LRS-75-24 is a 24-volt power supply with a maximum current of 3.2 amperes. According to the manufacturer, the unit operates at a mains voltage of 100 to 240 volts without an additional switch. It has no PFC function. The supply measures approximately 4 × 4 × 1 1/5 inches (99 × 97 × 30 millimeters) and is made on a printed circuit board fixed to the base of the metal case. The top cover is perforated, and the holes are meant for passive cooling.
The input and output circuits are connected to a common screw block (1). From right to left, there are 3 terminals for the input line, neutral, and ground wires, and terminals 4 and 5 are the outputs: ground and +24V. The input voltage goes to the fuse and inrush current limiter (2), then to the RF interference filter (3), and finally, to the diode bridge (4). The inrush current limiter has no markings; apparently, it is just an NTC. The rectified mains voltage is supplied to the 150 uF, 400V capacitor (5) and then to the flyback converter built on an MW03A controller (located on the back side of the PCB), a TK750A60F transistor (6), and a transformer (7). The voltage from the secondary winding of the transformer is rectified by a Schottky diode HBR20150 (8) and supplied to storage capacitors 2×470uF 35V, and, through an additional LC filter (10) (11), goes to the output. The feedback circuit is classic; with TL431 (on the other side of the board), the feedback signal is transmitted to the PWM controller through one of the optocouplers (12); the second optocoupler forms a backup channel for overvoltage protection at the OVP output. The installed electrolytic capacitors are designed for operating temperatures up to 220F (105C). The bulkiest of them, the input one, is held on the board with compound.
Build quality is good.
The power transistor (6) and diode (8) are pushed against the metal case using spring brackets to dissipate heat. Their own housings are insulated using special shells.
Test conditions
Most tests are performed using Metering Setup #1 (https://teardownit.com/posts/power-control-unit-for-testing) at 80F (27C), 70% humidity, and 29.8 inHg pressure. The measurements were performed without preheating the power supply with a short-term load unless mentioned otherwise. The following values were used to determine the load level:
Output voltage under a constant load
It should be noted that there is a slight overshoot; increasing the load slightly increases the output voltage. Power-on parameters Powering on at 100% load Before testing, the power supply is turned off for at least 5 minutes with a 100% load connected.The oscillogram of switching to a 100% load is shown below (channel 1 is the output voltage, and channel 2 is the current consumption from the grid):
The picture shows three distinguishable phases of the power-on process:
When connected to the grid, the pulse of the input current charging the input capacitors has an amplitude of about 7 A and a duration of about 5 ms.
Waiting for the power supply control circuit to start for about 88 ms.
(Output Voltage Rise Time) Output voltage rise takes 7 ms.
(Turn On Delay Time) The entire process of entering the operating mode from the moment of powering on is 95 ms.
(Output Voltage Overshoot) The switching process is aperiodic; there is no overshoot.
Powering on at 0% load
The power supply is turned off at least 5 minutes before the test, with a 100% load connected. Then, the load is disconnected, and the power supply is switched on. The oscillogram of switching to a 0% load is shown below:
The picture shows three distinguishable phases of the power-on process:
When connected to the grid, the pulse of the input current charging the input capacitors has an amplitude of about 5.7 A and a duration of 6 ms.
Waiting for the power supply control circuit to start for about 117 ms.
(Output Voltage Rise Time) Starting the converter, increasing the output voltage,...
Intermittent faults ('floating' defects) are damages that manifest themselves periodically and are caused by poor-quality core connections or reduced insulation resistance. Customer complaints about short-term connection losses are evidence of defects of this kind. Such defects may appear due to mechanical damage to the cable (for example, in the event of vibration from heavy vehicles, rotary equipment, etc., nearby).
Typically, when a technician encounters this type of damage, he has to wait patiently for it to manifest itself, hoping the effect will last long enough to determine its location. There is no guarantee that the damage will reveal itself while the technician is on duty. The use of reflectometers allows one to automate this process and maximize productivity.
Some reflectometers have a special function for detecting intermittent faults. The device connected to the line accumulates all reflectograms over a certain period and displays them superimposed on each other. Where the reflectogram differs, the intermittent fault is located.
Finding intermittent faults
For example, consider the following situation: a particular pair of cables works fine for the better part of the day, but there is a momentary failure out of the blue.
We get two reflectograms for the same pair (with different gain settings) when checked. In the first one, with a gain of 12 dB, a surge of positive polarity is observed on the reflectogram of a working pair at a distance of 6760 feet, corresponding to the end of the cable. In the second one, when the gain increases by 14 dB, an additional spike appears on the reflectogram, the nature of which indicates the presence of a coupling in the cable at a distance of 3280 feet. By further increasing the vertical gain level, the reflectogram will not reveal the slightest sign of damage along the entire length of the cable being tested.
We will need the 'intermittent fault detection' function mentioned above. By continuously monitoring the pair's condition, the OTDR shows any deviations from the cable's rated impedance, allowing the location of intermittent faults to be pinpointed.
The reflectometer display will show the current reflectograms obtained during testing. Periodic inspections allow one to determine whether signs of malfunction have appeared. Once the non-persistent damage has been captured, the result should look approximately as shown in the figure.
The differences will be evident if one compares it with the previous one. A noticeable drop appears where there was nothing before. The location of the fault can be determined by simply moving the cursor to the front of the pulse reflected from the break and reading the distance from the display.
Random vibrations or other irregular events cause the connections to loosen and electrical contact to be temporarily lost, resulting in a fault similar to a partial break. Note that at the moment this fault occurs, the pulse reflected from the far open end of the line decreases because, due to a poor connection in the cable coupling, the magnitude of the electrical signal reaching the end of the cable is reduced.
What conclusions can be drawn? Almost every type of cable system is susceptible to intermittent faults. Such damage creates severe problems for users and technicians. The intermittent fault detection mode of reflectometers allows one to continuously monitor the cable over a long period, so the technician does not have to waste working hours waiting for the damage to manifest itself.
Pupin coils
Pupin coils can still be found on an analog telephone line. Pupin coils disrupt the homogeneity of the copper pair, turning it into an ideal low-pass filter with more substantial high-frequency attenuation.
Therefore, a prerequisite for using any xDSL technologies on existing phone lines is the removal of Pupin coils, which have been found to have extensive applications in US telephone networks. Servicing xDSL systems can always...
Sometimes, a microcontroller does not have enough pins to receive signals from buttons or display them on LED indicators, control relays, etc.
Sometimes, one needs to interconnect two digital devices with a single cable, and it would be great to transmit eight, sixteen, or more signals over two to three wires to avoid needing a thick cable.
Or, let's say we just want to make a lighting effect for a street sign. One does not need a whole computer or a microcontroller for this task. All these cases (and many others) should be designed with shift registers.
As children, many of us had an NES (Nintendo Entertainment System) game console. Its gamepad had 8 buttons: a plus-shaped button for left, right, up, and down, then Select, Start, A, and B. And there were only five wires in the gamepad cable: ground, +5-volt power, and three signal wires. Meaning the state of eight buttons was transmitted over three wires.
In the core of the gamepad is a single CD4021 chip. It is an 8-stage parallel input/serial output shift register. Here is a diagram of its internal logic: the chip has eight inputs for parallel input and outputs from the last three flip-flops.
This should look familiar to our audience: a sequence of synchronous D flip-flops passing the torch of data bits from one to another. Oh, that's our combination lock from the post on flip-flops!
The CD4021 chip has two operating modes: serial and parallel. In parallel mode, eight flip-flops store information from eight inputs, each individually, regardless of clock pulses.
In serial mode, at the edge of the clock pulse, each subsequent flip-flop receives a data bit from the previous one, and the first flip-flop gets an incoming one from the serial input.
Then, where is the input pin to reset all flip-flops? The answer is there's none. However, you can pull the serial input low and send eight consecutive clock pulses. If necessary, we can write zeros to all memory cells. Although, in the case of a gamepad, one can do without it.
Simply switch the chip to parallel input mode, and it will save the state of the buttons. Pressed-down buttons correspond to logical zeros; released buttons correspond to logical ones because parallel inputs of the CD4021 in the NES gamepad are pulled by resistors to the power supply positive.
In this case, the DATA wire connected to the output of the eighth flip-flop will contain the state of the button S8 ('A'). We switch the chip to serial mode, apply clock pulses, and read S7 ('B'), then S6 ('Select'), all the way to S1 ('Right').
Congratulations! We have read the state of eight buttons via three signal wires (plus two power wires). Then we toggle to parallel mode again, rinse and repeat. This mode toggling is performed lightning fast, and the player will feel like the console responds to button presses instantly.
But what if it’s the other way around, and one doesn’t need to read information from buttons but to write it into cells, for example, by lighting LEDs? Then, a shift register with serial input and parallel output will help.
An example of such a shift register is CD40194. Unlike CD4021, it has not 8, but only 4 digits. Yet it's got parallel output and input, as well as serial input, with the ability to shift both to the right and left!
Does the CD40194 have a serial output, though? I hear you asking. Of course, it has! Q3 will be the serial output when shifted to the right, and Q0 will be the serial output when shifted to the left.
The CD40194 also has a general reset input. And there are also two mode selection inputs: S0 and S1.
When S0 = 0 and S1 = 0, nothing happens. The chip does not respond to signals other than a general reset, retaining the saved 4 bits of information present at its outputs Q0..Q3.
When S0 = 1 and S1 = 0, a shift to the right occurs at the leading edge of the clock pulse, from Q0 towards Q3. And the value from the left-most serial input is written to Q0.
When S0 = 0 and S1 = 1, a shift to the left occurs at the leading edge...
What is the difference between LED strip amplifiers, LED amplifiers, and RGB amplifiers?
Only in words and channels.
LED strip amplifier is a general definition.
An LED amplifier usually refers to a single-channel device that operates with a white light strip. Another name is the DC amplifier.
WW LED Amplifier is a dual channel device for warm and cool white light temperature strips.
An RGB amplifier is a three-channel device that produces red, green, and blue color strips.
The RGBW amplifier is a four-channel device for red, green, and blue color strips, with additional white LEDs.
The RGBWW amplifier is a five-channel device for red, green, and blue color strips, with additional warm and cool white LEDs.
Why do you need LED amplifiers?
Conductors always have resistance. Imagine we want to install an LED strip around a 500-square-foot room (16*32 feet). We need 96 feet of LED strip, and it is impossible (!) to connect it to the power supply at one point (!). Why?
For example, a strip has a power consumption of 3 watts/foot (a 16-foot reel has a power rating of 48 watts and a current of four amps at 12V). A 16-foot strip comprises 96 sections (cut lines) of two inches each. Each strip section will have an internal conductor resistance of 0.005-0.02 Ohms, depending on the manufacturing quality. The total native resistance of the strip is 0.48 to 2.8 Ohms. The supply voltage drop for the last sections of the strip will be 2 - 7.7 V. The voltage across the last sections of the strip will be 10 - 4.3 V. This is very low!
When all three channels are on, we will clearly see the difference in brightness between the beginning and end of a 16-foot strip. For an RGB strip, it will look like a color change. The start of the strip will be white, and the end of the strip will be yellow.
Several solutions to the power problem exist for a long line of LED strips. The first option is to install a thick power cable next to the entire LED strip and connect it to the strip several times every 10-20 feet. For example, a 4*14 AWG cable. The solution is excellent and reliable but expensive.
The second option is the use of an LED strip amplifier. The device is a set of transistor keys for powering a powerful load controlled by a special signal. LED amplifiers allow us to use multiple power supplies, synchronizing powerful loads with a control signal. We don't need to run four thick conductors along the entire length of the RGB strip, but just install a few power supplies and amplifiers every 10-20 feet. We can also combine power supply options depending on the situation.
We will also need an RGB amplifier to connect more loads (LED strips) to the RGB controller output than it supports/allows. For example, the RGB controller is designed for a 100W load, but we want to connect 300W LED strips.
So, what can go wrong with such simple devices? When choosing from catalogs and online stores, you will see only two significant characteristics - operating voltage (5/12/24V), maximum output current, and the number of channels - three for RGB and four for RGBW. However, my experience has shown that not everything is shown in the documentation.
Lying about the maximum current
Amplifiers are DC-powered, and when all channels are switched on, the total current of all channels flows through the common power wire (5/12/24V). Therefore, the maximum total current through the amplifier is critical. Since we are describing an electrical circuit, it is crucial to know how strong the weakest link is.
Let's take a look at such an amplifier.
In the housing and documentation, the maximum current through the amplifier is 24A. But! The device uses disconnectable connectors, which...
As you know, a data cabling system consists of different segments. To connect them all and bring the data connection to the end user, it is necessary to make a certain number of crossings. Often, staff forgets to disconnect "old" lines. As a result, over time, parallel branches appear, and their presence can have a detrimental effect on the quality of services.
BRANCHES AS A SOURCE OF PROBLEMS
Parallel branches can make it difficult to serve clients and ensure system functionality. With the introduction of digital systems, the search for parallel branches becomes an increasingly important task since they negatively affect the operation of digital transmission systems and, even if in most cases they are relatively short in length, nevertheless lead to significant problems. The bramch creates a second path for digital signals transmitted on the main line, which travel along the branch and are reflected from its open end. Reflected signals (echoes) enter the main line, where they are mixed with "good" digital signals and negatively affect the quality of the transmitted data. Therefore, to ensure correct operation of the digital line, the branches must be disconnected completely.
When connecting to analog lines, branching also creates problems. For example, if there is a fault on such a branch, it may show itself in the form of a decrease in the quality of the transmitted signal.
Finally, unknown branches can affect the accuracy of diagnostic equipment, for example, when measuring cable capacitance and estimating the distance to a break using a capacitive bridge. An unknown branch increases the combined capacitance of the cable pair and causes a measurement error: for the tested pair, the calculated length will be greater than the actual length.
It is very important to have full information about all the parallel branches available on the line in order, if necessary, to select the correct algorithm for troubleshooting and eliminating the problem.
SEARCHING FOR THE LOCATION OF THE BRANCH CONNECTION
The capacitive bridge is the device most often used to measure the length of a cable that is open at the far end. Unfortunately, it only allows one to estimate the total length of a cable pair, including all parallel branches.
Using multi-function devices (combining a capacitive and resistive bridge), it is possible to calculate the length of the branch cable due to the ability to compare the length values obtained from measuring the cable capacitance and the resistance of the loop.
Pic main_img_p7621_thumb.png
In this case, an OTDR is the most optimal and, moreover, the only device that allows one to find the locations of branching, measure the lengths of the branches, and determine the distance to them.
However, in practice, cable analyzers that combine the functions of a reflectometer and a multi-function instrument are more convenient. The implementation of two measurement methods (reflectometric and bridge) in one device allows for comparison of the results obtained for more accurate fault localization.
The classic branch reflectogram is similar to the one for testing a damaged cable, the only difference being that the reflection of the signal from the branch is a straight line rather than a curve.
As an explanation, let's look closely at the reflectograms for an open-ended cable section without a branch and a cable section with one (it is located at a distance of 3385 ft). The corresponding measurement results using a capacitive bridge were transferred to the reflectometer for direct comparison and accounted for. Note how the presence of a branch affects the measurement results of a capacitive bridge—in particular, how the cable section with a branch distorts the pulse reflected from the open end of the cable at a distance of 6500 feet. This occurs because part of the energy of the reflectometer signal was lost passing through the branch. The ideal way to view these graphs simultaneously is to use a dual-channel OTDR...
SW1 - circuit sensitivity switch for measuring Inrush current
SW2 - zero-cross switching on and off
SW3 - instant switching on and off for inrush current measurements
T1 - current transformer, 10A, 1:1000
U1 - Solid State Relay, zero-cross, controlling voltage 90–250 VAC
AC-synchronized switching on and off
If the device requires zero-cross on-off switching, the operator should use SW2, while SW3 should be open. In this case, the SW1 should be switched to the lower position according to the diagram. Then, 10A of the grid current will correspond to the connector J2 voltage equal to 1V. In synchronous mode, the on state of SW2 corresponds to a continuous mode; the value of the source current can be easily measured by briefly connecting the ammeter to the output terminals of SSR U1 without changing the position of the switches. With this measurement method, the ammeter does not risk being overloaded by the shock current of turning on the device. Asynchronous switching on and off When measuring INRUSH CURRENT, the operator should reduce the sensitivity of the current measurement circuit (upper position for SW1 on the diagram), open SW2, and use SW3 to turn on the device. In this case, 10A of grid current will correspond to a voltage at connector J2 equal to 0.1V. Since powering on will be accidental relative to the source phase, the measurement procedure should be repeated several times (at least ten). Only then can the maximum and average values for the INRUSH CURRENT be reliably determined.
Assembly
The described power control unit was assembled on a breadboard with a 0.1-inch pitch; the look of the unit is shown in the photos below:
On view 1 of the power control unit in the foreground, one can find the terminals for connecting the source and the device under test, switch SW2, and current transformer T1:
Power control unit view 2:
Power control unit view 3 shows the current sensitivity switch SW1 and connector J2:
Usage example
For example, if one uses the device to test a power supply, then with an oscilloscope, one can determine the following characteristics of the unit:
SETUP TIME Time to set up from the moment of applying the input voltage until the output voltage reaches 90% of the rated level at 100% load.
RISE TIME Time for the output voltage to rise from 10% to 90% of the nominal level.
HOLD UP TIME Time to keep operating at 100% load from the moment the input voltage is turned off until the output voltage drops to 90% of the rated level.
FALL TIME The output voltage decay time is 90% to 10% of the nominal level.
To be more accurate, it sounds like a valve stack; after all, it is a British pedal imitating British Marshall amplifiers.
Don't tell anyone because it's a secret: when creating his JTM45, Jim Marshall actually copied the circuitry of a 1959 Fender Tweed Bassman 5F6-A.
And Mr. Marshall also equipped his first 50-watt combo amplifier, a 1961 JMP Tremolo “Bluesbreaker,” with four 10-inch speakers. The iconic 2x12" version was made a year later.
Tolex instead of tweed, a horizontal arrangement of tubes, and ring-shaped loudspeaker magnets—the differences end there.
But why does the British Marshall sound so different from the American Fender? Is the difference really just the Celestion speakers instead of the Jenhsen ones with their U-shaped magnetic core?
The stronger magnetic field of British loudspeakers compresses the sound's dynamic range to a significant extent. One can compare the waveforms recorded with the Shure SM57 microphone from the 12" Celestion G12M Greenback and Fender Mustang II (V1) loudspeakers, as well as from the 8" Orange Voice of the World PPC108.
But the spiciest part of the Marshall sound is literally based on the usage of British valves instead of American tubes.
In the post about a simple DIY tube guitar amplifier, we already noted that the sound of a particular tube depends on the geometry of the grids and anode.
And if we compare 12AX7 preamp tubes with ECC83, we will see and hear that they are all very different. This is determined not by an American or European stamp but by the design of this particular unit from a particular manufacturer.
It's a completely different story with the EL34 and 6L6 power amplification output tubes. Their sound difference is on another level. Short and thick American 6L6 can be described as high fidelity with a large headroom; long and thin English EL34 is, on the contrary, a growling and roaring powerhouse due to the fact that it tends to limit and distort the signal.
Does this mean that if you swap the speakers and tubes in the Tweed Bassman and Bluesbreaker combos, the Fender 5F6-A would become a Marshall JTM45? Not really, no.
In the universe of guitar amplification, nuances matter: the cabinet's open or closed back wall, the fine selection of component values, and the frequencies to which the tone controls are set.
And, of course, the sound is influenced by the anode supply rectifiers and the supply and output transformers. And according to some experts, even the material of the chassis matters: the windings of transformers have considerable leakage inductance, and their alternating magnetic field interacts with the metal of the chassis.
Then there's another question: is it possible to emulate all these effects without real tubes, bulky loudspeakers, and heavy multi-pound transformers? A guitar amplifier is a complex yet still measurable device; it's subject to the laws of physics and can be mathematically evaluated.
There is no doubt about the possibility of recreating a certain sound by other means. The question is how complex the circuit with transistors and ICs will be sufficient to obtain a convincing effect.
The idea to replicate the iconic sound of the Marshall JTM 45 and JCM800 in a pedal body and create the world's first amp-in-a-box, oddly enough, first came to none other than the employees of the Marshall company itself, led by the head of the Development Department, Steve Grindrod.
Guitarists worldwide owe a debt of gratitude to this man for developing the legendary Marshall JCM800 and Vox AC30.
Today, the godfather of British Sound owns his company, Steve Grindrod (Albion) Amplification. He produces Pendragon guitar amps and Gypsy Boy acoustic amps and works with various charities. And in 1988, his efforts led to the creation of the Guv’nor pedal.
In 1992, the pedal was re-released under the name Drive Master. It differed from the original only without an effects loop jack.
The circuit looks like a regular distortion pedal with two operational...
HDMI stands for high-definition multimedia interface. Since it has HD in the name, it should be easy for anyone to guess when it was first introduced and implemented, raising 'HD' on the flag is so early 2000s. HDMI is a digital interface that was and still is competing with DisplayPort. The crucial thing in this standoff was that DisplayPort was always meant for computers and all the alike. At the same time, HDMI was developed by a consortium of consumer tech manufacturers, including TV makers. Historically, this meant a much greater spread of the technology, so any new type of device should have HDMI if it supports an external display for any purpose.
Just to keep this explanation fair, DisplayPort still has one undoubtedly significant advantage—native support for Thunderbolt USB-C. Thunderbolt and USB-C are complex standards, so I won't dive deep into this. It should be noted that if you have a fairly recently produced laptop computer with USB-C, then connecting it with a USB-C to DisplayPort cable is simpler compared to a USB-C to HDMI converter. This makes no difference to 99% of users, but an unnecessary converter can bother some.
All that aside, back to the topic. HDMI has gone through several versions. Usable (or, should I say, meaningful) ones right now are 1.4b, 2.0, and 2.1. This hot take and all the following could be technically incorrect, but are a good rule of thumb to evaluate cables and devices:
HDMI 1.4b is a version with a 10 Gb/s transmission rate, used for FullHD (and up to 1440p with some limitations) and basic additional functions like HDCP, ARC, Ethernet, and CEC.
HDCP is a content protection protocol used from the beginning of HDMI and is closely tied to it. In simple terms, it is here to ensure that the system's endpoint is indeed a monitor and not streaming or recording equipment. Suppose one tries to stream an HDCP-protected Netflix show from a laptop to a streaming box with no HDCP support (like some enterprise screen-sharing solutions). In that case, the image on the screen will be just black.
ARC stands for 'audio return channel'; video and audio signals are sent to the TV, video is shown, and audio is transmitted back through the same HDMI cable to be played on the player's, console, or PC side. The easy way to play sound on some standalone audio system instead of TV speakers is, of course, a trusted audio jack output on the TV. Using ARC is the right way to do it with an amp or an audio receiver near the media player. HDMI audio could be multi-channel, but the one-eight-inch stereo port is limited to just two channels.
Ethernet is an excellent addition to video and was added to the standard relatively early. It can be implemented on a single twisted pair inside an HDMI cable. Ethernet over HDMI is neither fast nor widespread, so the idea of ditching ARC and CEC (those wires are used for Ethernet) did not take off.
CEC is a basic, unified list of commands for consumer electronics, like 'on', 'off', 'switch to input 1', etc. CEC control is a type of protocol that requires no input from the user, and due to its simplicity, it is quietly implemented in most consumer media players. When the streaming starts, any Chromecast-like device does not hesitate to send out a few bytes to the TV to wake it from standby and switch to the appropriate input.
HDMI 2.0 is the one with 18 Gb/s throughput. This version can deliver 4K 30 frames per second with no color compression or up to 4K 60 fps with slightly reduced color space and no HDR. So if you plan on using a budget-friendly TV or a monitor—not a crazy bright one, not connected to a top-of-the-line gaming rig capable of outputting 4K at 120+ fps—then HDMI 2.0 transmitters, cables, and switches are fine. But if you do, then the next version is for you. Additional functions are static HDR (for 2.0a, dynamic for 2.0b), better and more capable CEC, and ARC.
'No color compression' means using the full 4:4:4 YCbCr color space. Number sequences 4:2:0 and 4:2:2...
===== After having some bloody eyes and reading your article I decided to change the firmware on shelly rgbw2 with ESPHome so I can modify the pwm freq to 1500 Hz like you recommended. Don't know if placebo or not but I feel better :) .
I can test only with camera from phone with shutter speed at 1/1500 and no flicker (and sub multiples like 1/500). With PWM freq at 600 Hz I could see flicker on camera at anything above 1/600.
Don't know if this is the same you have tested but I was curious if you can test with a modified Shelly with ESPHome to be able to put higher frequency. I also don't know if there is a limit on the maximum frequency (the shelly or the COB LED strip it's dimming ) it will work and if is there any benefit in increasing any further.
Thank you for publishing this extensive tests online. Ciprian =====
Once the WiFi network is configured, you need to use two commands through the Tasmota console (changes will be saved after rebooting or shutting down the device): SetOption68 1 // The device will switch to 4-channel white mode (if you need it)PWMFrequency 2000 // PWM frequency will increase to 2000 Hz
I set the PWM frequency by a multiple margin (I was just curious). 4000 Hz.
The optical measuring tool showed an incomprehensible picture for me. But this phenomenon is outside the scope of this post, and I will deal with it later.
Conclusions.
The Shelly device manufacturer can change and does change the PWM frequency in their firmware. I really don't understand their answer about not being able/unwilling to change the PWM frequency to a safe level.
I am very grateful to Ciprian for the excellent advice. Thank you, Ciprian!
Despite all the hard efforts to keep IT cables dry, water remains the most likely cause of cable failure. Water introduction into the cable leads to various types of damage, often resulting in a high-resistance short circuit.
Signs of cable water ingress change over time. Usually, the first symptom is the appearance of noise on the line. Interference occurs due to the flow of microcurrents between conductors. Suppose the service personnel do not take any measures. The problem may grow in that case, so communication will be blocked entirely. Cables with some water inside them can be categorized into two types: wet and waterlogged. Most of the time, the cable is simply soaked. In cables with filler, water can accumulate in existing voids and in overhead cables in sagging sections. In warm weather, it evaporates, and in cold weather, it condenses back again. As a result, the copper wires corrode, increasing resistance and causing poor cable performance.
Water ingress occurs when water penetrates the cable through a damaged jacket. In this case, the impact may come from groundwater, melting snow, precipitation, etc. A cable submerged in water may work normally until it inevitably does not.
SEARCHING FOR WATER INGRESS SPOTS
Water impact is found when the reflectometer detects a change in the resistance of the pair being tested due to a change in its capacitance. In addition, a good indicator can be the pulse propagation speed, which directly depends on the characteristics of the cable.
Water in the cable "slows down" the signal. In the waterlogged section, the electrical signal's propagation speed can change every other inch. As a result, measuring the actual length of the entire cable and its waterlogged section is much more challenging since the reflectometer measures time intervals. (The bridge meter will indicate that the cable length is longer than the actual length.) Water significantly increases the capacitance of the waterlogged section of the cable, so it will not be possible to find the correct propagation coefficient value. To reliably measure the cable length, one usually measures the length of a dry section, either on one or both sides. If the total length of the cable is known, subtract the lengths of the dry sections from it. Very often, the starting point of the waterlogged segment is too close to the reflectometer connection point. In this case, the device will not detect the presence of water. Therefore, the cable must be checked from both sides.
Some OTDRs have a "marker" function to measure the distance between two points, eliminating the need to measure dry sections on both sides of the cable and making it easier to determine the length of a waterlogged section.
The figure shows that L2 = Lcable – (L1 + L3), where L2 is the known cable length and L1 and L3 are dry sections.
Water ingress affects the operation of multiple cable pairs. When testing a disconnected or inactive pair, there is a possibility that some voltage may be induced by neighboring active pairs, which is why most testing methods, such as using bridge meters, lead to distorted results. In such a situation, a reflectometer is the only device that will allow one to find the water damage point.
The classic reflectogram of a waterlogged cable has three key features. The first is a decline in the reflectogram (reflected pulse of negative polarity) in the place where the section of the waterlogged cable starts. The second is a waterlogged segment of the cable, usually having a slightly curved characteristic with "noise" (this is not noise per se, but simply an impedance unevenness that causes a characteristic distortion to appear on that section of the cable). Finally, the third is the rise of the reflectogram at the end of the waterlogged section of the cable (the reflected pulse of positive polarity). The reference reflectogram in the figure illustrates the ideal case.
It is important to emphasize that the water in the cable significantly...
The RSP-320-24 is a 24-volt power supply with a maximum current of 13.4 amps. The supported mains voltage is from 100 to 240 volts without an additional switch. The supply measures 8.5 × 4.5 × 1¼ inches (215 × 115 × 30 millimeters), made on a printed circuit board fixed to the base's case. The top cover is perforated at the back near the connection terminals and on the front, where the cooling fan is installed. The fan starts spinning even if there's no electrical load. As the load increases, the fan speeds up, following the load current value. The fan sucks in the air and pushes it through the internal case volume to the perforated holes, including those on the side walls.
The input and output circuits are connected to a standard screw terminal block (1), from right to left: 3 terminals for the input line, neutral and ground wires, and 3 in parallel for common and +24V output. The input voltage from the terminals goes to the fuse (2), then to the pulse limiter (varistor), followed by the RF interference filter (3), and finally to the diode bridge (5). Next comes the active PFC, controlled by the PFC+PWM controller FAN4800 (4). Indeed, with a 234-volt AC power input, we get a rectified voltage on the storage capacitor (8) of 377 volts, approximately 47 volts more than without PFC Boost. The small voltage reserve is confusing since the capacitor installed is rated for 180 uF and 400 volts. All that's left is to rely on Nichicon's quality control.
The power part of the PFC is made of two parallel MOSFETs, IPP60R280P6 (7) and on an ultrafast diode 8A 600V STTH8S06D (6). The temperature sensor (11) is mounted above the PFC elements. The output voltage from the PFC is supplied to the two-transistor forward converter; the transistors are IPP60R280P6 (9) and are controlled by the same FAN4800 controller. The transformer (10) converter voltage is rectified and supplied to the LC filter. The output rectifier comprises eight diodes connected in two parallel groups (12). Total output capacitance: 2 pieces of 1000uF, 35V, designed for operating temperatures up to 220°F (105°C) (13). The output high-current circuits are reinforced with tinned copper busbars.
The control signal from the high-voltage side to the low-voltage side is transmitted through transistor optocouplers (there are two of them in the photo above the transformer hidden under a blob of the compound). One optocoupler is the primary regulation channel, and the second forms a backup channel for overvoltage protection, OVP.
The block diagram in the datasheet shows the "Active Inrush Current Limiting" node. Still, we could not find components on the board that could perform such a role. Still, the inrush current limitation element is present, marked as RTH1 on the board, and installed near the boost inductor PFC; most likely, this is an ordinary NTC.
The high-voltage part of the board, starting with the capacitor (8) and ending with the transformer leads (10), is coated on the high-voltage side with a protective composite, presumably epoxy-based, which further increases electrical safety.
There is additional insulation and a thin sheet of fiberglass between the aluminum case and the board (solder side).
The overall build quality is good.
Test conditions
Most tests use metering circuit #1 (see appendices) at 80°F (27°C), 70% relative humidity, and 29.8 inHg pressure. The measurements were performed without preheating the power supply with a short-term load unless mentioned otherwise.
The following values were used to determine the load level:
Output voltage under a constant load
The high stability of the output voltage should be noted.
Power-on parameters
Powering on at 100% load
The power supply is turned off at least 5 minutes before the test, with a 100% load connected. The oscillogram of switching to a 100% load is shown below (channel 1 is the output voltage, and channel 2 is the current consumption from the grid):...
First of all, you should pay attention to the ROM used. The flash-ROM chip from an old computer motherboard has a finicky parallel interface where the address is written in two runs. This complicates the operating logic and increases access time. Additionally, the PLCC housing it comes in can be expensive and challenging to install manually. In this regard, it was decided to replace it with a more modern 39-series microchip from SST. These chips, such as the SST39LF and SST39VF, have faster access times (55 ns and 70 ns, respectively) compared to 270 ns for the 49 series chip. This allows one to reduce data preparation time to one cycle. The SST39VF010-70-4C-WHE chip has been ordered.
It is also necessary to replace the RAM. To save money, I picked one that operates precisely at 3.3 V and has TSOP housing. The IS62LV256AL-45TLI chip was ordered.
The CPLD chip remains unchanged.
These updates improve overall efficiency by reducing memory access times and using more convenient and modern components, which can also improve product availability and reliability in the future.
The updated diagram is shown below:
The timing diagram for new chips has become much more straightforward:
After the final selection of the main components, a printed circuit board, which had specific requirements, was created. The board had to be adapted for manual assembly. Due to this, components were placed on one side of the board, and the number of pinout components was minimized, leaving only external connectors.
50 copies of printed circuit boards were ordered. This introduces the risk of the first boards' errors and inaccuracies, leading to scrapping all fifty and re-ordering the whole batch. Also, along with the boards, a stencil for applying solder paste was ordered. This will simplify the assembly process.
While waiting for the boards to be manufactured and delivered, it was time to think about flashing and testing the finished boards. Flashing CPLD was less difficult and could be done using a separate connector and USB programmer. However, programming the character ROM seemed more questionable. On a development board, to reprogram the firmware, the chip had to be carefully removed from the breadboard panel, inserted into the programmer, erased, flashed, removed, and returned to the breadboard panel. These operations turned out to be quite labor-intensive. Therefore, to program the character ROM, it was decided to use the tools of the CPLD itself through a custom parallel interface. There were two possible implementation options:
1. ROM programming with special firmware installed in the CPLD, intended exclusively for ROM programming. 2. Implementation of ROM programming functionality into the working CPLD firmware.
The second option was more complex and required additional CPLD resources that would only be used once or twice in the device's lifetime. Fortunately, there were enough CPLD resources available to implement the second option.
The finished prototype was tested through the same parallel user interface, displaying the test picture on the screen. To do this, I utilized an old laptop with an LPT port, which provided enough I/O lines to transmit all the necessary signals to the device.
The testing device (diagram above) was assembled on a breadboard using the surface-mounting method. The resistors were installed in the housing of the DSUB25 connector, and the tested or programmed board was connected with long and flexible pins.
When bending, the contacts create tension in the board hole, ensuring reliable contact. 2 kOhm resistors, together with pull-up resistors of the LPT interface (approximately 1 kOhm), form a voltage divider. This divider converts the 5V logic levels of the LPT port to 3.3V ones.
The board is powered through a simple linear stabilizer, getting a voltage of 5 V from the laptop’s USB connector. Resistor R4 with a resistance of 10 ohms is used for current protection. Suppose a short circuit or other problems are on the board under...
Sometimes, when making your own devices on microcontrollers, there is a need to display huge amounts of information on a display and to use a bigger screen for ease of perception. Unfortunately, there are no ready-made and budget-friendly solutions for this task on the market. LCD displays with the ability to connect to a microcontroller are usually tiny and pricy.
But at the same time, there is a wide selection of legacy LCD monitors with a VGA interface. Models with a diagonal of 15 to 19 inches can be purchased in perfect working condition for a very low price, or one can even get one for free. This especially applies to monitors with a 4:3 aspect ratio. In addition, such models are usually quite reliable.
Most older monitors only have a VGA connector for connecting to a computer. Sometimes there is an additional DVI port (on more expensive models). The HDMI connector is more common on modern devices.
Thus, with a probability close to 100%, we'll get just a VGA on an older monitor. In order to display an image on such a monitor, it is enough to work with only five signals: analog R (red), G (green), and B (blue), responsible for the brightness of each color component, as well as digital HS (horizontal sync) and VS (vertical sync), providing synchronization. Analogue signal levels should range from 0 to 0.7 V, where 0 V corresponds to no light at all and 0.7 V to maximum brightness. Digital signals HS and VS are short pulses with a TTL level of negative polarity. The timings of these signals can be found, for example, here: http://tinyvga.com/vga-timing/640x480@60Hz.
Typically, special controllers, or FPGAs, are used to generate video signals, and many FPGA development boards are already equipped with a VGA connector. However, FPGAs are often expensive and require many additional components. I was looking for a simpler and cheaper solution. As a result, the decision was made to use CPLD. CPLDs have fewer available logic gates (LEs) than FPGAs but are less expensive. For example, the MAX II Altera EPM240 development board is sold on Aliexpress: https://www.aliexpress.us/item/3256804686276488.html for only $8.12 (excluding shipping), and the kit even includes a programmer. The chips themselves can be purchased for $1.6–2.1 (for nice knockoffs).
Plain text mode was chosen for implementation because it is easier for a slow microcontroller but at the same time quite informative. Some graphics elements can be implemented using pseudo-graphics symbols, as was often done in the days of DOS. The introduction of a graphics mode would require transferring a large amount of data from the microcontroller and additional efforts to create it, which is not always possible, especially for weak cores.
CPLD has a built-in Flash ROM (User Flash Memory block, UFM), which can be used as a character ROM. However, its capacity is very limited—only 8 kbit, or 1 KB. This amount of storage is only sufficient for characters with a resolution of 5×7 pixels, and only if we discard non-displayable, insignificant, and visually identical characters from the ASCII table. In addition, the use of UFM will require the use of logic gates (LE), of which there are already a few. Despite the attractiveness of this option, I had to abandon it and use an external ROM chip, which can be salvaged from an old motherboard. Choosing a microchip with a supply voltage of 3.3 V will eliminate problems with matching voltage levels for the CPLD. The capacity of such ROMs is quite large: 2, 4, or 8 Mbit, or at least 256 to 1024 KB, which allows one to store a large number of different fonts with a decent resolution of 8x16 pixels.
To store the screen image, you will also need a RAM chip. Let's estimate the approximate size required for this. If we plan on using an 8×16 pixel font on a screen with a resolution of 640×480 pixels, we will end up with 80 characters per line and 30 lines on the screen. Thus, saving the screen image will require 80 ×...
Power-on and parameters characterizing the behavior of the power supply when turned on
Powering on the AC/DC source can be separated into the following phases:
Connecting to the grid, charging the input capacitors
Preparing the power supply control circuit for switching on
Starting the control circuit
Output voltage increase, entering the operating mode
INRUSH CURRENT
Peak input current at full load.
An excessive current value can cause false alarms on protection circuits and interfere with neighboring devices in the power line. Considering that nearby devices at risk could be computers, home automation control systems, etc., the cost of damaging them in such an event can be huge.
The INRUSH CURRENT value depends on the power supply circuit, the instantaneous value of the voltage in the grid at the moment of powering on, and the residual charge of the input capacitors before switching on. To reduce the INRUSH CURRENT value, both parametric (the most common is the introduction of NTC thermistors) and current-limiting circuitry methods to cap the charging rate of capacitors are used.
SETUP TIME
Time from power-on until the output voltage reaches 90% of rated voltage at full load
It affects the readiness time of powered devices, which is essential in many industrial applications: automation, redundancy schemes, etc. This time is not critical for domestic applications and can reach several seconds.
As a common rule, the power-on circuit determines it to the greatest extent and depends on its state at the time of switching on. To a lesser extent, it depends on the input voltage at the moment of switching on and on the residual charge of the input capacitors.
RISE TIME
The time it takes for the output voltage to rise from 10% to 90% of the rated level at full load.
Usually, this is several tens of milliseconds. Mainly depends on the power supply control scheme.
How to measure these characteristics
One can use the power management diagram at the end of this document to obtain the power-on characteristics. You need to connect the AC input to the power source and connect the power source under study to the output. Connect the channel 1 probe of the oscilloscope to the source output and set the vertical sensitivity so that the expected output voltage of the source conveniently fits on the screen for observation. Set the triggered sweep threshold to 0.7 of the expected voltage. Set the horizontal scan to 20 ms/div. Set the launch moment to position 0.8 from the full horizontal sweep.
Connect the channel 2 probe of the oscilloscope to the measuring output of the power control circuit and set the sensitivity to 0.5 V/div.
Ensure the power control unit's current transformer mode button is pressed.
Keep the circuit off for 5 minutes, switch the oscilloscope to standby mode, set the load to 100% power, and turn on the circuit.
Evaluate the use of the vertical and horizontal dynamic range for the resulting oscillogram: the processes should occupy from half to the total size of the screen; single limitations of the signal "hairpins" along the vertical are allowed. If the display conditions are not met, adjust the gain and/or scan and repeat the power-on procedure from the beginning.
Determine parameters using cursor measurements on the oscilloscope screen.
An approximate view of the oscillogram obtained using the described method is shown in the figure:
These characteristics are consistent with a device having an active PFC circuit and an active inrush current-limiting circuit. It can be seen that the SETUP TIME is 263 ms, and the RISE TIME is 8 ms.
Power-off and parameters characterizing the behavior of the power supply when turned off
Switching off the AC/DC power supply can be separated into the following phases:
The supply continues to operate due to the residual charge on the input capacitors until the voltage across them drops to a certain critical level; at this point, maintaining the output voltage at the nominal value...
Programmable power supply for external/target devices
The PiEBridge has a built-in programmable power supply for external/target devices. The user can set the voltage of 2.5-5V (accuracy not less than 2%) with a current not more than 300mA by command from SBCs (e.g., Raspberry Pi).
Users can set this programmed voltage or "ground" to any pin of the output connectors using the built-in 3*10 pin matrix and jumpers.
Connectors
The PiEBridge extension board has built-in 6-pin IDC (2x3 0.1") and 10-pin IDC (2x5 0.1") output connectors. We recommend using four basic adapters to connect to target systems (e.g., for flashing) via these connectors:
The primary and most common damage types are wire casing damages or cable installation errors. These typically are 'floating' defects and wire connection errors. Let's learn the technique of searching for those kinds of faults.
AUTOMATIC DEFECT SEARCH
Let's start with the automatic search mode. This method automatically compares defects detected on the reflectogram with a threshold value of reverse attenuation. The method of automated comparison with a threshold value greatly simplifies reflectogram viewing. If, for example, you set the threshold to 30 dBRL, the reflectometer will automatically display only the faults with a return attenuation value of 30 dBRL or less.
FIXATION OF 'FLOATING' DEFECTS
Locating 'floating' defects is another indispensable function of a modern reflectometer. Only with its help can it be possible to point out the locations of the periodically repeating effects of weak wire connections or reduced insulation resistance. Defects of this kind manifest themselves in customer complaints about random signal loss. 'Floating' defects can appear for various reasons: when a signal is applied, due to mechanical stress on the cable at the point of damage (for example, vibration from nearby operating equipment like an elevator), etc.
The inconsistent nature of 'floating' defects complicates their localization; it becomes possible only if the data is accumulated over a relatively long period (sometimes up to a day). To solve this problem, some reflectometers implement a special intermittent fault detection function. When activated, the device connected to the line accumulates all reflectograms and displays them overlayed on each other. The 'floating' defect shows up as the difference in graphs. It is enough to connect the device to the line and leave it for the period during which the defect is guaranteed to appear.
SEARCHING FOR CROSSED CABLE PAIRS
Resolving cross-pairs in structured cabling systems is extremely difficult. Finding them takes much longer than finding any other damage.
Fixing such damage is much cheaper than replacing the entire cable or laying an additional one. Using an identification tone and an OTDR is one of the simplest methods for quickly and reliably locating tangled wires. First, you should understand the causes and symptoms of the malfunction. We must remember that mixing up wires is a human error. This malfunction appears mainly at cable splices (in couplings) when two wires of the same color but belonging to different pairs are connected. This situation usually results in unacceptable crosstalk. Most often, this happens due to the inconsistency of the twist and the susceptibility of the untwisted cable pair to parasitic signals. As a result, the wires act as antennas. In addition to receiving a strong spurious signal from external sources, the untwisted pair itself has increased radiation and has a negative effect on the remaining pairs in the bundle. The primary way to solve the problem is to fix the defect in the next cable coupling line. We are talking about restoring the correct connection (and, in fact, about re-tangling the same wires). This is the simplest solution, which, of course, does not eliminate the problem. In any case, this section of the cable must be repaired.
FINDING THE SPOT OF THE BREAKAGE
The instruments used to test cables are often unable to detect mixed pairs. For example, a bridge-type meter turns out to be ineffective. This device combines an AC bridge (capacitive bridge) and a DC bridge (resistive bridge). The capacitive bridge will show a fault in the cable. It will be able to determine the length of the defective section of the cable since the reversed pair has a reduced capacitance. However, it will not allow you to determine the distance to the place where the mix-up occurred. A resistive bridge is unsuitable in this case since mixing up the wires has virtually no effect on their resistance.
Note that some reflectometer models have a function...
The LRS-150-24 power supply can operate from a 100–120 volt or 200–240 volt AC network. The manufacturer states it provides an output current of up to 6.5 amperes at 24 volts. The supply measures 5¾ × 3¾ × 1¼ inches (145 × 95 × 30 millimeters), made on a fiberglass printed circuit board fixed to the base's case. The top cover is perforated in a honeycomb pattern. The case and cover are both made of aluminum.
The board is put together neatly, with no visible defects. The components are arranged evenly, and soldering was done with a no-clean flux. Absolutely nothing dangles or rattles in the assembly.
No noises of any sort were noticed during the operation of the power supply.
The power supply uses a flyback circuit without PFC.
The input voltage is supplied to the input node: RF interference filter (1), a pulse surge limiter (varistor), then the voltage goes to the diode bridge (2) and two input electrolytic capacitors (3). The input voltage selector is also located here. Flyback, built on a MW03A controller (4, installed on the back side of the board) and a power switch (5) on a N-channel MOSFET transistor MMF60R290P. Unfortunately, there is no information about the controller on the Internet. The transistor has a channel resistance of 0.29 ohms at 650 volts and 13 amps. The transformer (6) is entirely covered by the casing, so it is unclear what core material is used. The output rectifier (7) is built using a Schottky diode HBR20150 in a TO-220F package screwed to the side wall and covered with casing. It is basically dual 150V 10A diodes connected in parallel. After the diode there are four output electrolytic capacitors (8) and an additional LC filter. Here (12), there is a small output voltage indicator (green LED) and a regulator (tuning resistor) for adjusting the output voltage. Input and output circuits are connected through a shared screw 7-terminal block (10). 3 terminals for the input line, neutral, and ground wires, and 2 in parallel for common and +24V output.
The main electrolytic capacitors are designed for operating temperatures up to 220°F (105°C), Rubycon. Two optocouplers (11) are installed in the feedback circuit, most likely with phototransistors transmitting control signals from the low-voltage output to the high-voltage input side.
The board has a few cutouts to increase the dielectric strength between the high-voltage and low-voltage sides of the circuit.
The picture shows that the board has three unused spots for storage output capacitors (8), most likely used in the other power supplies of the same series but with different output voltages.
Test conditions
Most tests use metering circuit #1 (see appendices) at 80°F (27°C), 70% relative humidity, and 29.8 inHg pressure.
The measurements were performed without preheating the power supply with a short-term load unless mentioned otherwise.
The following values were used to determine the load level:
Output voltage under a constant load
The high stability of the output voltage should be noted.
Power-on parameters
Powering on at 100% load
The power supply is turned off at least 5 minutes before the test, with a 100% load connected.
The oscillogram of switching to a 100% load is shown below (channel 1 is the output voltage, and channel 2 is the current consumption from the grid):
The picture shows three distinguishable phases of the power-on process:
The pulse of the input current charging the input capacitors when connected to the grid has an amplitude of about 7.5 A and a duration of 2 ms.
Waiting for the power supply control circuit to start for about 100 ms.
(Output Voltage Rise Time) Starting the converter, increasing the output voltage, and entering the operating mode) is 8 ms.
(Turn On Delay Time) The entire process of entering the operating mode from the moment of powering on) is 119 ms.
(Output Voltage Overshoot) Output voltage overshoot is absent; the switching process is aperiodic.
"PiEBridge" is an extension board for microcomputers similar to the Raspberry Pi (Pi), which is designed to be a helper for the DIY-maker in all his activities - Pi, together with PiEBridge, can perform a variety of functions:
universal programmer
software and hardware debugger for target systems
PCB fusion furnace controller
smart-home controller
as well as do many other useful things
You might say Pi already knows how to do these useful things, so why does it need more extension boards? Here is the answer to that question:
PiEBridge transforms the Pi's 40-pin I/O subsystem into more practical 6/10-pin lines for many applications and provides signal integrity for these lines
adds the simplest controls and indications (button, pedal, and LEDs)
has a programmable 2.5...5V power supply for external devices
"Naked" Pi is usable in two extreme configurations - either just a box controlled externally via SSH or a desktop computer with a monitor, keyboard, and often even a mouse. In addition to these typical use cases, PiEBridge allows you to use the Pi as a standalone software automaton to perform random repeating tasks with minor interactive operator participation.
PiEBridge is plugged into the Pi extension connector (compatible with family models with a 40-pin connector) and installed vertically. For this purpose, the Pi case (if available) must have a corresponding cutout on top.
When used as a programmer, PiEBridge can work with most known 6-pin and 10-pin connectors, and GND and Vcc can be randomly connected to their pins to ensure compatibility.
The programmable power supply for external devices is programmable on/off and programmable in the range of 2.5 - 5V with an accuracy of about 2%.
Deb-packages for PiEBridge have been created and compiled into a repository:
general-purpose, providing configs and libraries for working with controls and indications, as well as with the power supply
special purpose, e.g., applications for MCU and FPGA programming and debugging
auxiliary purpose, for example, for repeating operations automation (like mass-production function for firmware flashing). In this case, the user can use settings that provide autonomous launching of the necessary software when the Pi is turned on, and then (after finishing its work) its simple parking and shutdown by pressing and holding the button for a long time.
metapackages, which cause installation of necessary software and configs for the selected role and allow to simplify preparation for work
The accuracy of reflectograms, the reliability of the conclusions made, and the time spent on diagnostics largely depend on the set of additional functions of a particular device.
A modern reflectometer must meet the following requirements: • have a decent amount of memory for storing reflectograms with workable resolution; • be able to exchange data with a computer; • have two channels for comparison and differential mode support; • automatically calculate the return loss value.
Other useful features that make the operator’s job easier, thus worth mentioning: • automatic search for defects when viewing a reflectogram; • automatic two-dimensional scale adjustment to fit the most significant defect found; • distance measurement between two points or cursor positions on the reflectogram; • registering transient or "non-persistent" faults.
Introduced as another means to simplify the operation, some of the functions mentioned above had a revolutionary impact on fault localization techniques using reflectometers. So they are worth a closer look.
Saving reflectograms to memory
Thanks to this feature, measurements themselves do not require any specific knowledge, and qualified specialists can analyze the results later. Suppose the initial cable parameters were set incorrectly. In that case, the needed information can always be clarified, and using the saved data, the results can be reprocessed without going back to the site.
Data uploading to and downloading from a PC
Uploading data to the cloud or to a computer provides the possibility of archiving and further processing. For example, reflectogram files can be viewed, printed, scaled, compared, superimposed on each other or on a trace diagram, sent, etc. Reflectograms can be processed using proprietary (supplied by the manufacturer) and open (particularly graphic editors) programs. If necessary, files can be sent for analysis to a more experienced specialist. A critical point should be made: the reflectogram file can be loaded back into the reflectometer’s memory, for example, for comparison with a new reflectogram at the diagnostic site.
Dual channel
Two measuring paths allow one to take reflectograms simultaneously from two pairs and display them for visual comparison. Some devices also implement further processing of the received reflectograms.
Comparison and differential modes
These two modes greatly simplify the localization of the main fault against the background of numerous synchronous interferences (repeating reflections from the input of the device, reflections from couplings, inserts, branches, etc.). The amplitude of the signal reflected from the main fault in the line could be less than the amplitude of these interferences. Suppose one receives signals from both faulty and serviceable pairs of the same cable. In that case, their overlay (comparison mode) or subtraction (differential mode) will allow one to identify differing sections of the reflectogram, i.e., exactly those places in the characteristic where the faulty pair does not coincide with the working one and where the defect is probably located.
Differential mode is more convenient—the reflectograms of the damaged and good pairs are subtracted, which leads to compensation for almost all synchronous interference. It is much easier to identify differences this way than by eyeballing them. Using this mode, damage locations are clearly visible on the difference reflectogram. If the device is dual-channel, both reflectograms can be obtained in real-time. Such devices are simply irreplaceable for localizing places where pairs have been damaged due to improper connection of wires (decoupling).
In devices with built-in memory, comparison and differential modes are implemented using reflectograms obtained in real-time from two different channels of the device or by processing saved reflectograms created as a result of the last measurement and stored in the device’s memory. The latter mode provided a revolutionary ability to diagnose...
I almost built a 1954 Regency TR-1 superheterodyne transistor radio.
It was the very first commercially available radio receiver in the United States and globally, built entirely on transistors. How much have inner and outer designs changed in 69 (excellent) years?
The 1954 Regency TR-1 was not just portable but pocket-sized. And not just pocket-sized but autonomous and battery-efficient.
Pocket crystal radios, such as the popular back-in-the-day rocket-shaped ones, have been around for a long time. They required grounding, so listening to the radio while walking was impossible.
The earbud cable performed the antenna function as somewhat recent cell phones with FM receiver functions. And the decorative antenna at the top of the rocket was a tuning plunger for moving the induction coil of the resonant tank core.
There were pocket tube radios in the 1950s. But an expensive set of anode and incandescent batteries lasts for just 5 hours. And almost all such receivers could only be listened to with an earbud.
There were a few loudspeaker exceptions, like a 1954 Hoffman Nugget sub-mini tube pocket radio made in Los Angeles, California.
Two marks on the receiver scale in the form of a triangle indicate 640 and 1240 kHz, the frequencies for the public warning system. In the 1950s, it became clear how important small, self-powered radios were in an emergency. This spurred demand for such receivers.
And this is a loud-speaking 1953 Emerson 747. It was too quiet, so in 1955, the low-frequency tube output stage was replaced with a transistor one. The new model received the number 838.
The Emerson 838 was called the world's first transistor radio in ads. However, it was a hybrid tube transistor and the all-transistor Regency TR-1 had already been released a year earlier.
It was a revolution, both technically and aesthetically. The Regency TR-1's case set the standard for radio design for decades, and no doubt even influenced the appearance of the Apple iPod.
Note that a thumbwheel instead of a knob was first used not in transistor receivers for the sake of compactness but in old RF-tuned radios for a completely different purpose.
For loud-speaking reception of a signal from a powerful station, it is enough to connect an audio amplifier to the crystal radio output. And to hear a distant station, one needs to amplify a weak signal using a radio frequency amplifier.
The problem here is that the strong signal of a nearby station will not vanish into the blue. One or even two LC-resonant tanks will not be enough to suppress unwanted signals and highlight the desired ones. Therefore, a nearby station (and also interference from car ignition and other electric motors nearby) will sound louder than a distant one.
RF-tuned receivers were created with three, four, and even five resonant tanks, like the 1927 Leutz Transoceanic "Phantom" to mitigate this issue.
Linking the shafts of three or five variable RF-tuned radio capacitors mechanically and settling for just one tuning knob is, at first glance, a bad idea because it is difficult to ensure stable equality of the resonant frequencies of all resonant tanks in each position of this knob.
Therefore, the creators of such receivers supplemented each variable capacitor with a dedicated adjustment regulator. Unlike the knob, which is supposed to be turned with a two-finger pinch, the thumbwheel can be rotated with one finger. Thus, one can learn to adjust three or even four circuits simultaneously.
It would be even better to make one large knob with a vernier, a reduction gear with a scale that turns the shafts of all variable capacitors, and connect an additional small variable capacitor in parallel to each big one for fine-tuning. But this would lead to a cost increase for the receiver as well as an increase in weight and dimensions.
But one can choose another path. When we tune a guitar by holding the second string at the fifth fret and listening to its sound simultaneously with the first string,...
IntroductionWhy use HDMI over IP in some cases? The image quality is noticeably worse than a classic HDMI twisted-pair extender. Let's see a few examples and answer this together.
When is the best case for HDMI over IP extenders?
Previously, we have repeatedly compared two types of HDMI extenders with each other:
HDMI over twisted pair cable
HDMI over IP extender
The second type also works over twisted pairs, but it has the additional ability to operate in populated local networks.
Upon reading our posts, you may think using the first type of extender is always better. After all, it is indeed better in many respects: ideal video quality, no transmission delays, and many supplemental functions. The only thing is to stay within the twisted pair cable length limits, usually up to 330 feet.
But it is only sometimes the case.
Sometimes, having a separate twisted-pair cable from the video source to the TV makes it impossible to install a transmitter and receiver of the first type. But suppose there are available wired Ethernet sockets somewhere near both installation spots. In that case, the extender of the second type is a good option.
Sometimes, installers plan on remaking an existing LAN, adding separate twisted-pair cables for video transmission of the first type, and turning to us for advice. The initial idea is to disconnect two sections of twisted-pair cable from the router:
from the video source to the router
from the TV to the routerand connect both lines together.
At first glance, we will see a twisted-pair cable from the video source to the TV. So we should be able to use type 1 extenders, right? Although it is theoretically possible, the probability is extremely low.
We will have the following connection between the transmitter and receiver: HDMI transmitter - patch cable - LAN socket - twisted-pair cable - connector - twisted-pair cable - LAN socket - patch cable - receiver.
The first type of extender is very picky about the cable's construction and the connections between the transmitter and the receiver. Firstly, one must use twisted-pair cable of a category no lower than specified in the manual. This is usually CAT6, CAT6A, or better. Secondly, there must be a solid piece of twisted-pair cable between the HDMI transmitter and receiver with no breaks or lower-quality connectors, like wall sockets.
The second type of extender works like any other LAN device. So, we can use LAN sockets, patch cords, routers, and switches.
Of course, expensive professional solutions with low video compression levels exist. The quality of the video output from the receiver is hard to distinguish from the original. The transmission delay is almost invisible to the human eye. Such equipment has strict requirements from the manufacturers in terms of IP-network parameters; they usually do not recommend using an existing network.
In our post, we will skip this case and look at more down-to-earth options for the average user.
So what are you going to do if laying a separate whole piece of twisted pair is not on the options list? First, you must determine what you will connect to the remote TV. Suppose this is a DVR located somewhere in the attic or garage. In that case, you can safely use an HDMI over IP extender connected to the existing LAN network.
Let's look at one of the devices of this sort and try it in real-world conditions. We'll use the INRIKS EX2073KVM extender as an example.
Device description
The INRIKS EX2073KVM is an HDMI and USB transmitter and receiver kit twisted-pair cable with a range of up to 390 feet. The kit operates "over IP," so the receiver can be connected to the transmitter with a single piece of twisted pair and via a local network.
The maximum video resolution is 1080p at 60 Hz.
In addition to video, the EX2073KVM can transmit a USB 1.1 signal, which is sufficient for a USB keyboard and a USB mouse.
Let's look closer at the package contents and the typical connection.
Let's see how the cables measure influence the range of the reflectometer. How do the noise filtering mode and methods for determining the unknown propagation coefficient affect the measurement accuracy?
KEY FACTORS FOR CABLES
The reflectometer's detection range depends on the cross-section of the cable cores, the overall quality of the cable, as well as on the way the reflectometer is connected to the cable being tested. The larger the cross-section of the cable cores, the less attenuation the electrical pulse supplied by the reflectometer to this cable undergoes and the longer the distance it covers. Old or defective cables may have reduced insulation resistance or increased attenuation. This significantly reduces the ability of the cable cores to conduct electrical signals and, as a result, reduces the maximum distance. The connection of the reflectometer to the cable must be done so that a pulse with the maximum possible amount of energy is emitted from the reflectometer to the cable.
NOISE FILTERING
I want to eliminate the noise in more detail, as it is on any cable. Many reflectometers have a digital noise filtering mode that obliterates the noise from 50 Hz to 1 GHz. This mode is designed primarily for lineworkers dealing with cables near sources of strong electromagnetic interference (for example, railway contact networks, power lines, or antenna poles). The operator can select a filter type with the required characteristics for each test to ensure the acceptable quality of the resulting reflectogram. Suppose an unexpected random voltage value appears in the line during the measurement. In that case, the noise-filtering mode gets turned on automatically. A multi-level and multifunctional filtering system allows one to check antennas and cellular nodes with some received signal interference.
In some cases, the noise-filtering subsystem may slow down the OTDR operation to such an extent that the display becomes unusable. A good example is filtering the noise the power supply induces (60 Hz). One period of alternating current with a frequency of 60 Hz is 16.7 ms. Therefore, it also takes 16.7 ms to generate one point on the reflectometer display. It will take no less than 5.12 seconds to refresh all the 256 image pixels on the display. One way to compensate for this delay is to store the denoised reflectogram. Writing data to the device memory will take some time, but subsequent operations will be as fast as if the filter were turned off.
The "averaging" mode, often provided by the manufacturer to eliminate interference at maximum gain, is no exception. This mode also decreases the refresh rate of the display. Four times less noise means the screen is refreshed sixteen times slower. When the image refresh speed is reduced significantly, it becomes difficult to work with the display, so this mode should be used only when necessary. One more thing to mention: cables for digital data transmission should be tested using short pulses with a duration of 2, 10, or, in extreme cases, 100 ns. They do not affect nearby pairs under load, so the data transmission devices' error detection system will not flag them as such.
PROPAGATION COEFFICIENT AND METHODS FOR ITS DETERMINATION
As already mentioned, the reflectometer determines the distance to the abnormal spot based on the signal propagation speed in the cable and the time it takes to reach the point in question and return. In most cases, speed is expressed as a unitless coefficient, the ratio of the signal propagation speed in a given cable to the speed of light. It is an empirically determined value. Reflectometers from different manufacturers require one to set the wave propagation speed, called the Velocity of Propagation (VOP) or Velocity Factor (VF). Typically, this parameter is expressed as a fraction of the speed of light and can have a value from 0.3 to 1. A cable with a VOP value of 0.66 allows an electrical signal to be transmitted at 66% of the speed of light. Some manufacturers...
We have many years of experience in developing electronic devices for various customers. When we complete a non-standard task, we often explore new methods and ways to achieve the required result. By accumulating this knowledge, we create solutions to simplify the design and creation of devices. It's time to share some of our solutions with the community now.
Core team:
• 3 full-time hard/firmware engineers • 15-30 years in product R&D and systems engineering • full range of product development jobs: - highlighting the problem - transforming it into a task - searching for possible solutions based on target parameters - analysis and selection of the best option
Application and system programming:
• core team programming languages: C/C++, ASM • compilers: C /C++ (CLI): GCC, IAR, SDCC, C++ Builder, Avocet C, Hi-Tech C • IDE: SlickEdit, emacs, IAR Embedded Workbench, Multi-Edit, eclipse cdt, STM32CubeIDE, Atmel Start, Atmel Studio, NetBeans IDE, Qt Creator • make, cmake, qmake, cvs, subversion, git, etc • experience/projects: - embedded programming z80, MCS-51, AVR, PIC, ARM (7, 9, Cortex), STM8 - RT-tasks under eCos - eCos modules - in-house RTOS for telecom equipment - special Windows-NT services for own hardware - BDOS/BIOS CP/M for Z80CPU hardware emulator - desktop applications for Windows/Linux
Circuit engineering:
• analog: automation, data acquisition, measurements, sound, etc • digital: from simple logic circuits to FPGA/MCU/PSoC • power electronics: experience in DC/DC up to 600W • experience: PSpice, VHDL, Verilog
Electronic devices R&D:
• PCB/PCBA TH/SMD/multilayer w/auto testing @ production cycle • PCBA (bare and cased) thermal calculations • calculation and design of pulse transformers and inductors • 3D housing design • experience: KiCAD, Altium Designer, FreeCAD, OpenSCAD, Fusion360 projects: - wide spectrum of microcontrollers - telecommunication equipment (about 1M subscribers in service) - time measurement equipment for telecom - hardware emulator with a signature analyzer
Signal distortion induced by electronic devices, primarily amplifiers, could be either undesirable or useful.
When we play back an audio recording, we want it to sound as close to the original as possible. Or sometimes, we want to add just a smidge of tube distortion.
On the other hand, magnetic recording on tape and mechanical recording on vinyl, by their nature, significantly alter the sound; therefore, distortions are deliberately added into the circuits of recorders and playback equipment so that, in the end, the resulting audio signal turns out to be indistinguishable from what has been recorded.
In addition, volume controls are equipped with loudness compensation to account for human hearing abilities.
Mobile pocket audio devices have tiny speakers, and their power amplifiers are specifically designed to add bass and limit treble so that the sound is deeper and less squeaky.
Multi-way speaker systems have filters, and sometimes even separate amplifiers, that slice the sound signal into frequency bands for each dedicated speaker: subwoofer, low-frequency, mid-frequency, and tweeter. These can also be considered deliberately created distortions.
Finally, processing an electric guitar signal requires numerous fine-tuned distortions. They form a wonderful guitar tone. But if we simply plug the best electric guitar into a hi-fi amplifier, we'll be disappointed.
One can also identify a malfunction by the specific distortions of the signal and, by tracking the signal flow, specify the location of the malfunction in a complex circuit.
A device that allows you to see distortions is called an oscilloscope. But having an oscilloscope is not enough; we will also need a standard waveform signal generator. Today, we will assemble three such generators.
So-called standard waveforms are sine, triangle, and square. Devices that generate such signals are called function generators.
A sine wave is the simplest signal, but it is the most difficult to create without an LC resonant tank, using only RC circuits. A pure sine wave oscillates one frequency; it is needed to determine the harmonics the circuit adds to the signal.
For example, in this image from the post about the tube amplifier, we see that the upper half-wave is wide and rounded, and the lower half-wave is narrow and pointy. This indicates the presence of a second harmonic, which makes tube amplifiers sound so beautiful.
A triangular waveform could be created by a ramp voltage generator. Such a signal allows one to see nonlinear distortions as lines bend on the oscilloscope screen.
Bending them a certain way brings the triangle line closer to a sinusoid. This is exactly how the function generators on microchips that we are studying today are designed.
An ideal square wave consists of vertical and horizontal lines. Looking at the flow of such a signal, one can see the frequency-dependent deviations, interference, and parasitic processes.
For example, a differentiating circuit with a time constant of an order of magnitude smaller than the period of the input signal creates a sharp peak at the beginning of the horizontal section.
And this is what the result of the operation of an integrating circuit with a time constant comparable to the signal period looks like.
If the integrator time constant is noticeably smaller than the signal period, then only the leading edges become sloped, and the top part of the square wave remains flat. In this oscillogram, we see additional high-frequency interference.
Here, we see not just high-frequency noise but damping oscillations excited by sudden changes in the input signal. Such vibrations are called "ringing".
Function generator on the XR2206 chip
Our first generator can produce electrical oscillations with frequencies ranging from 1 Hz to 1 MHz. This is more than enough for an amateur's lab.
The 300 kHz square wave we have here is distorted not by the generator itself but by the DSO112A oscilloscope, whose analog bandwidth is 2 MHz....
The reflectometer's capabilities in terms of maximum distance and damage detection accuracy are determined by the sensitivity of the amplifier and some other important parameters.
Amplifier sensitivity
The sensitivity of the reflectometer, along with the pulse amplitude, is one of its most essential characteristics. It determines the maximum operating range of the device. It is crucial if you're going to check cables with high signal attenuation. Technical documentation often skips this parameter or describes it very vaguely. In an ideal scenario, sensitivity should be characterized as the input voltage when the waveform on the instrument display is contained between the top and bottom edges of the screen (i.e., “x mV for full-screen deviation”). Vertical sensitivity is sometimes measured in decibels. The decibel value is relative and has no meaning unless given a reference level of 0 dB. With this data, the amplifier's sensitivity can be calculated, as each 6 dB step doubles the gain. Based on the parameters mentioned above—pulse amplitude and amplifier sensitivity—it is possible to calculate the maximum overlapped line attenuation, which also serves as a criterion for assessing the quality of TDR. The maximum overlapped attenuation (amax) is defined as the line attenuation when the deviation of the vertical beam is at least one-eighth of the full screen. In this case, amax is calculated using the formula:
Amax = 20 lg8 + 20 lg(Upuls/ampl), - Amax is the maximum attenuation, - Upuls — pulse amplitude under load Zo, - Vampl — amplifier sensitivity for full-screen deviation.
It should be mentioned that this method can only be used to compare reflectometers from different manufacturers. It will be impossible to accurately calculate the maximum attenuation overlapped by the reflectometer using this method since the attenuation in metal cables is frequency-dependent. Therefore, different duration pulses will correspond to different Amax values. The covered method for estimating overlapped attenuation better suits optical TDRs. Optical fibers have frequency-independent attenuation, and therefore, in optical time domain reflectometers (OTDR), the pulse amplitude and sensitivity of the photodetector are usually not taken into account; they are "integral" parameters of the device. A parameter called "dynamic range" is introduced instead, i.e., the insertion loss of the line, at which the signal-to-noise ratio SNR = 1 for a certain duration of the probing pulse. To widen the dynamic range of OTDR, one needs an increase in probing pulse power and the receiver's sensitivity, as well as a very specific set of digital processing algorithms developed by the manufacturer.
Resolution and accuracy
[illustration from viavisolutions.com]
Before discussing the issues related to resolution and accuracy, some basic concepts should be defined.
Display resolution is the interval between two consecutive dots on the screen. Fault detection resolution is the minimum distance between two consecutive faults to be visible as separate faults on the reflectometer display. Sampling precision is just the precision with which samples are carried out. The term "fault localization precision" also speaks for itself.
Fault localization precision
The accuracy of finding the fault in the vast majority of real-world cases is limited by the availability of reliable information for the cable being tested and not by the sampling precision or display resolution of the reflectometer. Firstly, the pulse propagation coefficient can only be known with an accuracy of a few percent, and on top of that, it is affected by temperature changes. A 1% error in setting the pulse propagation coefficient leads to a 1% error in determining the distance. Secondly, the limited information on the actual cable route, in turn, limits the user’s ability to find a point along the cable...
The project was created by accident at the moment of urgent need for a mobile standalone device for ISP programming and testing a lot of printed circuit boards with controllers and FPGAs. The task was quickly solved on a Raspberry by assembling a small IDC-10 socket adapter with a button and LEDs on a breadboard and installing OpenOCD and xc3sprog packages.
It became a solution, after which any thoughts about buying or upgrading another programmer just disappeared. In fact, if you have been working with programmable devices for a long time, you can surely find a whole museum of such devices for flashing (I have a whole drawer of them on my nightstand) - ByteBlaster, Segger, (maybe even several), ST-Link, etc., but there are many of them! These devices are built for LPT, COM, USB... lots of different ones, but here's the trouble - many are already old, unsupported, and incompatible. We'll have many more other reasons to finally buy a new one already. You know? And instead of all this happiness!
The advent of small and low-cost Linux microcomputers with GPIOs has allowed desktop applications to access external devices without special adapters, dongles, etc., leaving only electrical matching necessary.
Many projects immediately used this opportunity but also immediately raised the problem of unification on the use of GPIO (lack of unification). And this requires a solution.
Project Objective
The first project objective is to create extension boards for Linux microcomputers with GPIO, containing minimal indication and control elements and a small connector for connecting external devices with unified access to them.
Why do you need a board like this?
In most practical applications, the extension connectors of these microcomputers are redundant. For example, a cursory review of published Raspberry application projects shows that you will often find that 10-pin will suffice.
For the same reason, the same 40-pin connector is impractical (and more often - simply impossible) to install in the target device, and this means that somewhere, there must be a transition, a bridge to a smaller connector.
Serial matching is very useful (and sometimes necessary) when connecting devices, for which, for example, Segger has a special adapter. Raspberry has no matching elements, so they must be placed somewhere. By the way, these elements (resistors) are useful for another important reason - they effectively reduce the risk of GPIO damage.
A microcomputer, equipped with a minimalistic interface on a few LEDs and buttons, is freed from the monitor, mouse, and keyboard from the constant "tutelage" of the host-PC and becomes a handy standalone tool for a pervasive class of routine and cyclic tasks, such as: - programming, diagnostics (JTAG interface provides access to various pins of the chip, which allows the creation of the necessary test conditions (logic levels on the pins) and reading the states; general tests are also possible), - electrical training (test (usually cyclic) operation of the device in specified modes. For example, at the initial moment of the device lifetime, detection of hidden defects is most possible (semiconductors, switching, etc.), so "runs" of devices in the correct modes at the factory and workshop are necessary to ensure that consumers receive the best quality devices by filtering out defective devices back at the factory), etc.
In fact, for example, what does the flashing process of a stack of assembled boards consist of? It consists of a sequence of actions: "plugin, start programming, wait, on a pass/fail signal, move to cell number either 1 or number 2, go back to the beginning". Ideal for a button and three LEDs.
GNOME Project, CC BY-SA 3.0 US, via Wikimedia Commons...Read more
The INRIKS EX4076KVM is a transmitter and receiver kit that allows HDMI and USB signals to be transmitted over twisted-pair cables for up to 230 feet.
Specsheet claims the maximum supported video resolution is 4K at 60 Hz.
The transmitter has an HDMI pass-through output port. It can help connect a nearby TV or monitor.
The receiver has a digital S/PDIF output for connecting an audio system.
The manufacturer does not specify the version of the USB standard. We assume this is USB 1.1, intended for connecting low-speed devices like a regular keyboard and mouse. So, the webcam most likely will not work with such an extender, but we will check it anyway.
Let's take a closer look at what's in the box and how everything connects together.
Visual overview
As usual, INRIKS ships out the EX4076KVM kit in a gray cardboard box with a brief description on a sticker.
Inside the box, one finds the transmitter and the receiver neatly tucked in soft-touch plastic baggies. Those are rare for INRIKS packaging, usually saved for a higher-level lineup of extenders.
Under the plastic tray, there are two PSUs, a USB cable, and a set of mounting brackets with a bunch of screws.
So the full kit of the INRIKS EX4076KVM is:
• Transmitter unit - 1 pc • Receiver unit - 1 pc • DC 5V/2A - 2 pcs • USB Cable - 1 pc • Mounting brackets - 8 pcs • Screw - 18 pcs • User manual - 1 pc
The transmitter and the receiver are both medium-sized, not compact, but feel solid in your hand. It's easy to spot high manufacturing quality right away. The entire case is made with minor grooves for better heat dissipation.
One side of both the transmitter and the receiver has the same set of interfaces, left to right: • a pair of LED indicators for USB (KVM) signal transmission and reception • Reset button • RJ45 port for twisted pair connection • LED power indicator
On the opposite side of the transmitter, left to right: • power connector DC 5V-12V • HDMI output for a local TV • HDMI input for connecting a video source, PC, or DVR • USB port for connecting to a video source
The opposite side of the receiver, from left to right: • DC 5V-12V power input • digital audio output (S/PDIF) • HDMI output for a TV • two USB ports for a keyboard and a mouse
One can call it just a standard set of interfaces, except for the loop-out HDMI on the transmitter and S/PDIF digital audio output on the receiver.
We have already covered the HDMI loop-out function in a separate post. It is basically a 1 to 2 HDMI splitter built into the transmitter.
It can connect a reference monitor, displaying the video identical to that transmitted over a twisted-pair cable to another room. Suppose you want to stream the same video simultaneously to both the remote room and the room with the video source (PC or DVR). In that case, you can do it easily with no external HDMI 1-to-2 splitter or additional cables needed.
As for the S/PDIF audio output of the receiver, this option will be of little use to anyone connecting an HDMI KVM extender to a DVR. Although it might be helpful to someone.
The sides of the housing have mounting holes for screws. The possibility of adding the brackets and the fact that they are included are undeniable advantages of this kit. With them, you can securely fix the transmitter and receiver to horizontal and vertical surfaces.
The holes allow the mounting brackets to be positioned in two planes, as shown:
The first option of bracket placement is used to secure the device to a horizontal or vertical surface by the majority. However, some professionals will be very grateful for the ability to install brackets...
The awesome Colpitts oscillator. Exploring the secrets of the Colpitts generator.
Hello, and welcome to our electronic studies! We probably all know that an oscillating circuit consists of a capacitor (C) and an inductor (L), and its waveform is an ideal sine wave.
In the LC resonant circuit, single-frequency oscillations occur, and their period in seconds is equal to 2π√(LC).
This equation is called Thomson's formula after its author, William Thomson, aka 1st Baron Kelvin. Many other things are named after him because Lord Kelvin was an outstanding scientist and inventor. One can recall, for example, the Kelvin, a unit of absolute temperature, or the marine compass with sundial he invented.
Another thing we know is that a transistor and an operational amplifier amplify the signal, meaning they transform a sin wave with a small amplitude into a sine wave with a bigger amplitude. We had 0.5 volts; it became five volts - ten times as much.
However, real electronic devices, even seemingly simple ones made from a handful of components, work in a much more complex and interesting way than the simplified idea of them from a school physics class.
This can either cause problems that we must learn to overcome or inspire technical creativity and help us achieve difficult tasks with simple components.
Today, we will study the operation of a real Colpitts oscillator, and a small printed circuit board and a digital oscilloscope will help us with this.
Edwin Henry Colpitts was a great inventor and a famous communications engineer. From 1897 to 1899, he served at Harvard's Jefferson Physical Laboratory. From 1899 on, Mr. Colpitts worked at the American Bell Telephone Company. In 1907, he became the research branch chief at the Western Electric Company. It was a manufacturing division of the American Telephone and Telegraph Company from 1881 to 1995.
Colpitz became vice president of AT&T in 1924 and was vice president of Bell Labs from 1934 to 1937. From 1940 to 1946, he served as head of technical aid for Division 6 (antisubmarine warfare) of the National Defense Research Committee and was awarded the Medal of Merit.
As often happens among renowned geniuses, Colpitz neglected his most known invention. He described the operating principle of his generator in a private conversation around 1915. He quickly forgot this product pitch, and later, according to company practice, he was asked to sign a patent application in 1918 (US patent 1624537).
A distinctive feature of the Colpitts oscillator is that the positive feedback for the amplifier (which can be a bipolar or field-effect transistor, an operational amplifier, or a vacuum tube) is received from a voltage divider on two capacitors connected in series and connected to an inductor.
The oscillation frequency is nearly equal to the resonant frequency of the LC circuit of two capacitors with an inductor parallel to them.
The actual frequency will differ from the theoretically calculated one due to the distribution of capacitances and the resistive load of the transistor. This is exactly what we will see on the oscilloscope screen.
The twin brother and probable predecessor of the Colpitts generator was the Hartley oscillator; a patent application for it was filed in 1915 (US patent 1356763, issued 1920). The difference is that a voltage divider for positive feedback is formed not by two capacitors but by two inductors in series or a single-tapped inductor.
The innovative feature behind the Hartley oscillator was that its coils did not have to be magnetically coupled, which was strictly necessary for its predecessors, the Meissner and the Armstrong oscillators.
Rhodes Scholarship winner Ralph Vinton Lyon Hartley, also known for pioneering the concept of "information" as a random variable and for attempting to define the "unit of measure of information", has worked for the Western Electric Company since 1915. He was in touch with Edwin Colpitts at the time and probably was a part of the aforementioned...
The general principle of operation of the reflectometer is elementary: a probing pulse is transmitted from the generator through a directional coupler to the cable; it is then partially (or completely) reflected back from impedance irregularities along the cable length. The reflected impulse arrives at the input of the device and, through a directional coupler, enters the receiving unit. This input signal is converted into digital format and shown on the display as a reflectogram; its form can be easily traced back to the known diagrams. Impedance abnormalities can be caused by various cable faults or external causes, like an incorrect plug-in.
For successful direct fault detection, two parameters are of particular importance. First is the maximum distance to the damaged spot when it can still be clearly identified. The second is the accuracy of determining the defect. Unfortunately, it is difficult for any manufacturer to comprehensively answer these specs because reflectometers can be used to test many different types of cables, primarily in real-world conditions rather than in a dedicated lab. Therefore, usually, device manuals contain a list of basic technical parameters. Key values predetermining reflectometers' maximum detection range and damage detection accuracy are the amplitude and duration of the probing impulse, as well as the amplifier's sensitivity.
The Pulse
Most reflectometers are able to generate probing pulses of various durations. Short pulses allow one to detect a faulty spot relatively close to the point of connection of the reflectometer; they also provide better search resolution, meaning it's possible to detect two individual damage points close to each other. Longer impulses help find remote faults in the cable as they carry more energy. However, the search resolution in this case is decreased.
It is a common misconception that decreasing pulse width necessarily results in increased accuracy. This is not entirely true. When using a reflectometer, the measurement is made along the edge of the pulse. Therefore, if the primary purpose of the test is to detect just the first fault, the pulse duration has virtually no effect on the accuracy of the pulse edge measurement. The main advantages of a short pulse are the narrowing of the so-called "dead zone" following the transmitted pulse and a corresponding improvement in resolution when detecting faults. The easiest way to explain the "dead zone" effect is by using the example of searching for two closely located damage points. Comparing graph shapes on the display for shorter and longer pulses, we'll clearly see that short pulses make both spots identifiable. But as the pulse width increases, the two spots become indistinguishable, as the dead zone covers the second one. The same logic applies to the case when the fault is too close to the connection point of the reflectometer: the initial pulse, due to its width, will mask the one reflected from the nearest damaged spot. Some OTDRs use balance adjustment to fix this issue. It allows one to effectively suppress the transmitted signal and display just the one reflected from a fault located too close to the device. Thus, it is not that necessary to use short pulses to detect defects up close. Using longer pulses provides another advantage; the never-ending problem of mitigating signal noise can be dealt with by increasing signal energy and, therefore, improving the signal-to-noise ratio.
If the reflectometer you currently have does not offer the ability to send short pulses and, moreover, there is no balance adjustment, then to detect damage up close in the cable, we can suggest a simple trick: you can connect a short piece of cable between the reflectometer and the cable being tested; this will allow you to "move" the damage point further away from the device. Just remember to use the same impedance cable as the one tested. And to minimize spurious signal reflections, the device's total resistance must match the extension...
Are you the type of person who likes listening to good ol' radio like I do? Unfortunately, medium-wave broadcasting has decayed in the last few decades. There's nothing in many areas, even at night when medium wavelengths work best. That’s why the radios from our childhood stay unused and collect dust.
Today, we will make a small medium-wave radio transmitter that can help you check and configure AM radio receivers and listen to music through them if you connect an MP3 player or smartphone.
The power of this transmitter is 0.0005 watts, and the range is about 3 feet, so you won't disturb your neighbors or need a license for it.
The transmitter is AMT-MW207 and was developed by an enthusiast under the nickname "Radio Lover". The circuit is proven to work perfectly and stays unchanged, but the layout of the PCBs can be different. For example, here is the newest and perhaps most nice-looking version 1.3 revision 2, dated September 15, 2022.
I've assembled ver. 1.2 rev. 7. It has a green board, no frequency scale, and the wavelength adjustment knob is located at the very bottom of the board. I consider these differences to be purely aesthetic. The transmission frequency can be viewed much more accurately on the screen of a separate frequency meter or oscilloscope.
Older versions are less convenient to attach the testing hook of the oscilloscope to, and they have no cutouts in the back of the PCB for winding up excess wire. The differences are generally insignificant; all versions of the transmitter work and sound the same.
The DIY kit was designed and kitted with passion: brass fittings, high-quality AA battery holders, and neat resistor value markings.
The potentiometer volume knob was not forgotten either; they also got me a good 3.5 mm TRS-TRS cable. In fact, this is an important detail. You sure can twist the variable resistor's shaft without a handle. Still, you won’t be able to connect a player or a laptop if there is no connecting cable. You won’t be able to try out a freshly assembled device, which will ruin the mood.
The transmitter circuit is simple yet elegant. Transistors Q1 and Q2 are a long-tailed pair, and Q3 is its current stabilizer.
A transistor current stabilizer is an emitter follower whose load is a resistor R6.
According to Ohm's law, the current through this resistor will be equal to the voltage across it divided by its resistance. The voltage at the emitter of a transistor connected to a circuit with a common collector is similar to the voltage at the base minus Vbe.
Vbe, the voltage between the base and the emitter for a particular transistor, is an almost constant value. Nothing is ideal, so Vbe actually depends on the temperature and base current, but these influences are tiny and can be ignored.
R3 and R4 together are a voltage divider. With a supply voltage of 6 volts, the current through this divider is 6V / (R3 + R4) = 6V / 59.2 kOhm = 101 µA. We neglect the base current of transistor Q3, which is connected in parallel with R4. I will explain why later.
The voltage at R4 is 101 µA * 8.2 kOhm = 828 mV. As Vbe = 0.63 V, resistor R6 gets the remaining 199 mV. Then, the current through it will be 60.3 µA.
The emitter current of transistor Q3 is the sum of its collector and base currents. The collector current is β times the base current, where β is the current gain coefficient of the transistor.
The average value of β for the 9011 transistor is 90. That is, the collector current is 60.3 µA * (β-1)/β = 60.3 µA * 89/90 = 59.63 µA.
The base current is 60.3 µA / β = 0.67 µA, less than 0.7% of the R3R4 divider current. Therefore, the base current can be neglected even in such a microampere case due to the fact that Q3 is connected as an emitter follower.
That is, it has a very high input impedance. It can even be calculated: Rin = Vin / Ib = 199 mV / 0.67 µA = 297 kOhm.
Even if our transistor has twice the current gain,...
We have already covered the topic of connecting a monitor, mouse, and keyboard to a PC (server, laptop, or DVR) at a great distance. The best option is to use an HDMI KVM extender over a twisted-pair cable.
With its help, one can complete the simple task of installing a DVR in one place, a monitor, keyboard, and mouse in another, and controlling the DVR remotely. In other words, using twisted pair cables, one extends HDMI and USB interfaces by 200–300–400 feet.
But what if the person needs to connect two different remote workstations for CCTV operators so that every one of them can see the image from the DVR and control it?
Let's try to solve this problem in practice using HDMI KVM extenders over twisted pair and see if it works out.
Required digression
First and foremost, I'd like to note that HDMI KVM twisted pair extenders come in two main types: 1. The transmitter and the receiver are connected to each other directly by a single piece of network cable. Such setups guarantee almost perfect image quality without any visible video distortion or transmission delays for HDMI and USB signals. 2. The transmitter and the receiver are connected to the local network. Both units encode and decode video signals, which, although just a smidge, negatively affects the image quality and increases the transmission delay, so one can feel a slight lag when using the mouse.
We think it is always better to try to use the first type of extender. Such devices deliver the best user experience of all.
On the other hand, sometimes, running a single dedicated twisted-pair cable between the transmitter and receiver is not at all possible. In this case, your only option is the second type of extender. Obviously, you'll need a LAN connection available on both ends :)
Therefore, we'll experiment with both types of extenders separately.
Extending the HDMI KVM interface to two different spaces with a one-piece twisted-pair cable
To assemble such a system, we used a pair of INRIKS EX4076KVMs. The kit includes a transmitter and a receiver. The INRIKS EX4076KVM can transmit 4K 60 Hz video with USB KVM up to 230 ft.
Thanks to the HDMI pass-through port on the transmitter, we can connect two transmitters, one after another, to the DVR. This way, we don't have to use a splitter to duplicate the HDMI signal.
As shown in the diagram below, we have connected all of our equipment.
Everything started working after powering on the equipment and a little initial delay. This startup delay is for all the video devices to sync. The video quality on the remote monitors was perfect; both mice worked simultaneously. We consider this test to be passed.
Extending the HDMI KVM interface to two different spaces over the LAN
We took two HDMI KVM extenders for this case over LAN INRIKS EX2073KVM. The kit extends 1080p 60Hz video and USB KVM over a network cable for up to 390 ft.
It should be noted that the kit uses an IP network, so we can use LAN switches to increase the transmission distance even further. For example, when using a single network switch, the distance will be "up to 330 ft." — "LAN switch" — "up to 330 ft."
Another advantage of HDMI extenders over LAN is streaming the signal from a single transmitter to multiple receivers ("one-to-many connection" in the manual). All the receivers will get the same picture from the transmitter.
We'll try to make use of this feature in our scheme. That means we'll need just the receiver from the second INRIKS EX2073KVM kit.
The manufacturer also states that although many EX2073KVM receivers can be present on the LAN, the mouse should be connected to only one of the receivers at any given time; the remaining ones are just there to show the image. We will check whether this claim is valid.
We have connected all of our equipment as shown in the diagram below and, according to the manufacturer's recommendations, just one mouse.
There is a short pause after powering up to sync all the devices, and everything's working as intended....
My first impression was that I had finally assembled the best overdrive in my entire life. For the first time, a cheap Squier Bullet Mustang electric guitar with stock humbuckers sounded equally good with all the cabinets I usually simulate and switch between when testing a new pedal.
Like my all-time favorite guitar, the semi-hollow-body Harley Benton TE-90QM with P90 pickups, this Squier Mustang can be called "moody." The beauty of its sound does not reveal itself with any overdrive or cabinet you pick at will. One must properly look for good-sounding gain and tone knobs positions.
The 2011 Gibson Melody Maker Explorer behaves completely differently than most other Gibson guitars. A deep and clear sound with no unpleasant overtones and no excessive protrusion of certain frequencies is obtained with almost any equipment of "good enough" quality in a much more comprehensive range of tone and gain settings.
Does wood affect the guitar tone?
It is common knowledge that the design of an electric guitar affects its sustain. The semi-hollow body transfers part of the strings' vibration energy to the air; the sustain is shortened, but the sound production nuances are emphasized, which is important for the blues.
Additionally, harmonics that make multi-layered chords with complex alterations sound ugly are also suppressed; this matters for various jazz styles.
A solid-body guitar retains the strings' vibrational energy, resulting in longer sustain. Even longer for a guitar with a glued set-in and, moreover, a set-through neck. But both the glued neck and, especially, the through neck soften the attack a little.
That is why many bluesmen prefer a Stratocaster over a Les Paul. Rhythm guitarists tend to like bolt-on neck guitars, while lead guitarists pick set-in and set-through necks. Of course, this rule of thumb depends on the person; each musician does their own thing. It could be playing DJENT on a Telecaster with a single pickup, like Rick Beato.
We are accustomed to the fact that a string is a stretched wire. But in a striking clock, the string is a metal rod, fixed on one side and not tensioned. The bass string in the clock is called "gong"; it can be very long and twisted like a spiral to fit into the case
The guitar's soundboard and neck combined are also very massive strings compared to the actual strings. And it's made of wood for the most part, so it is much less hard and dense than regular metal strings.
So, the Q-factor of the soundboard and neck oscillating system is much lower than that of strings. Meaning that the natural frequency vibrations of the guitar's neck and body decay much faster than the vibrations of the strings.
Therefore, wood has minimal effect on the actual sound timbre of an electric guitar. The signal passes through pickups, cables, pedals, an amplifier, a cabinet, and then a microphone with an equalizer; it's safe to say that wood does not affect the frequencies.
The sustain time of the body and neck's vibrations is much shorter than any noted time, but it is comparable to the attack time when one hits the string with a pick.
Very dense, hard, and heavy types of wood, such as rosewood, pao ferro, and ebony (listed in order of increasing density), respond to attack with a short, sharp snap. Thus, the wood of the fretboard emphasizes the attack.
Indian laurel wood, used for the fingerboard of the Squier Bullet Mustang, resembles rosewood in appearance but is softer. It can be compared to the roasted maple wood of the Gibson MM Explorer`s fretboard.
Mahogany's soft, relatively light, and moderately porous wood creates a longer, more profound, and softened response that hides shortcomings in sound production. The Gibson MM Explorer has a mahogany neck.
But if the guitar's neck and body are made of mahogany, the sound may be too dull, washed out, and mumbly. To add some brightness, maple wood is used. The Gibson Les Paul Standard has a top made of it, the LP Tribute has a neck, and the 2011 MM Explorer...
To localize defects in metal cables, there is a popular, widely used device — reflectometer.
Photo from website TEMPO ® (www.tempocom.com/products/cablescout-cs90/)
The reflectometer measures the reflection of a signal. This method for cable damage detection complements all the others we've previously discussed and, in some cases, gives more accurate results, especially when locating wire entanglements or breaks and looking for non-persistent faults. Furthermore, it allows one to clearly identify several individual problems when they interfere with each other, as well as determine the range of each one of them.
Reflectometers' principle of operation
The reflectometer detects irregularities in any wire line (in particular, in a symmetrical twisted pair) by measuring the reflected signal. To do this, short DC electrical pulses are applied to the cable pair being tested. Suppose there is an imperfection in the cable. In that case, some or all of the energy of the original DC impulse is reflected back. Both the sent pulse and all of its reflections are shown on the display. Impedance abnormalities could be of various origins; each of them has a unique reflection pattern. Thanks to this feature, it is possible to determine from the shape of the reflected signal not only the location but also the nature of the fault.
This principle of determining the state of a cable pair based on the parameters of the reflected pulse is called time domain reflectometry (TDR). At its core, it is identical to the radar principle used in radio systems.
The method of measuring the signal at the output of the line being tested (also called the incident wave method) provides only an integral assessment of the line's condition. It requires two devices: a generator on the transmitting side and a signal meter on the receiving end. On the contrary, reflectometry, firstly, allows one to estimate the quality of the wire at any point of its length. Secondly, a measuring device is needed only at one end of the line. This latter feature is the key for TDReflectometers to become as widely used as they now are.
To determine the distance to a particular fault spot or just an impedance abnormality of the cable, one needs to simply set the propagation coefficient and measuring range. The propagation coefficient defines the speed of the electrical impulse going through the cable of a particular type as a reference for the reflectometer. After capturing the impulse, the device will automatically calculate and display the distance to the damaged point of the cable.
Before looking into all the quirks and features of reflectometers, it is helpful to briefly describe the key features of a simple symmetrical twisted pair cable, as they are directly related to the reflectometer's operation.
It is well known that any symmetrical pair is a two-wire electrical line, and it is described as a chain of primary sections connected in series. Each section is a simple circuit, a four-pole unit consisting of active resistance R, inductance L, capacitance C, and active conductivity G.
When a harmonic signal circulates in a twisted pair circuit, the voltage-to-current ratio at each point is called the input impedance of the twisted pair. If a twisted pair is loaded at the end with a resistance equal to
where w=2pf, then it's input resistance will be equal to Zc anywhere along the line.
This input resistance for any twisted pair is its defining feature, and it is called wave impedance or characteristic impedance. In this ideal example, all the energy of the signal, when reaching the load Zc, dissipates completely from it. This characteristic is relevant for a specific cable length known as electrical length and listed in a spec sheet.
Suppose a twisted pair is loaded with a resistance ZL different from Zc. In that case, the energy of the probing signal is only partially absorbed by the load and partly directed back to the emitter. The relative measure of the power going back through...
One usually uses an HDMI cable to connect different video equipment. If the display (or a TV, monitor, or projector) is farther than 60 feet away from a signal source like an Xbox, we have to use an HDMI extender. Extenders over twisted-pair cables could be helpful even for distances smaller than 60 feet.
We must find another way to solve this when the transmission distance goes north from 400 feet. One of the options here is to implement HDMI over optical cable, a kit like the INRIKS EX2078A.
Features
INRIKS EX2078A is a set of transmitter and receiver units. It extends the HDMI signal with a maximum resolution of 1080p at 60 Hz for 24 miles.
The TX unit has an HDMI output for local monitoring TV.
In addition to the above, an IR return channel controls the playback source from the display end of the line with the remote.
Visual inspection
INRIKS EX2078A is shipped in a simple gray box with a sticker; all the basic features are listed.
Inside the box are both TX and RX units in a firm wrap. All the accessories and the manual are under the plastic tray that holds the transmitter and receiver.
So, the box contains:
- HDMI transmitter (TX) over optical cable, 1 pc.
- HDMI receiver (RX) over optical cable, 1 pc.
- Power supply DC 5V, 2A, 2 pcs.
- SFP optical transceiver (T1310/R1550nm), 1 pc.
- SFP optical transceiver (T1550/R1310nm), 1 pc.
- IR blaster extension cable, 1 pc.
- IR receiver extension cable, 1 pc.
- User manual, 1 pc.
Rx and TX units are pretty compact; their size directly corresponds to the ports on their back plates.
The face plate has LED indicators and a RESET button.
On the back plate of a transmitter, one can find a DC 5V input, an optical transceiver slot, an eighth-of-an-inch jack connector for the IR output, an HDMI input for the image source, and an HDMI output for the monitoring display.
The back plate of a receiver has basically the same ports: DC 5V input, optical transceiver slot, IR input, and HDMI output for the TV.
It's worth mentioning that we've got mounting brackets on the case to easily install it on any even surface.
And one more thing: the infrared emitter and receiver are included. With those, one can transmit the signal from the remote to the image source, which is miles away from it. More details on this feature are here (link).
As for the optical transceivers, there are two of them included in the box. The input optical interface is LC/UPC S. You should start by plugging in the transceiver labeled "RX" into the receiving unit; the other transceiver is supposed to be inserted into "TX" but does not have such a convenient label🙂
We've opened the case to check the quality of the materials and the soldering job. The metal case is fine and thick, would be very hard to bend, and looks and feels substantial.
The board is sitting in special cutouts in the case. It is securely fixed to the case with no slack. Openings for the ports are made accurately with no shifts or gaps.
The upper side of the PCB has no issues; everything looks neat. But the downside is the downside (pun intended); it has some unwashed flux stains around bigger elements and port connections.
Some soldering sloppiness never hurts, but we had to point this out.
Testing
For the test, we've got a laptop, a monitor, and a fiber optic cable.
Honestly, we cannot check if the range is indeed 24 miles, so we'll take the manufacturer's word for it. For the shorter distances, it does not matter if we use 50 feet or a mile-long cable, so we've settled for 50 feet of fiber that was lying around.
We connected everything according to the included manual.
We powered everything on, and after just a few seconds, there was an image on the remote monitor. Those few seconds at startup are necessary for both units to get synced.
The transmission lag is negligible. We've done several measurements, and it was somewhere between 0.06 and 0.1 seconds.
Transmitting a video signal over such a long distance makes the delay irrelevant....
Have you ever made a processor? I did. Took me just 12 microchips and a clock generator.
The processor can execute several commands, and programs can be written for it. The program code and input data are entered using micro switches, and the state of the output register is displayed by four LEDs, according to the number of bits.
At first glance, even this circuitry may seem very complex. Still, it consists of simple modules interconnected by data and control buses. Understanding each module's operation and interactions is relatively easy.
The primary function of a processor is to perform arithmetic and logical calculations. Therefore, our processor is naturally built around an arithmetic-logical unit (ALU).
As an ALU, we will use a full four-bit binary adder SN74HC283N. This chip is asynchronous; it adds two four-bit numbers and outputs a five-bit number (a four-bit number and a carry flag if there is an overflow).
If you are unfamiliar with the binary numeral system, it's high time to learn it. It is precisely the same as the decimal we're used to; its base number is 2 instead of 10.
0000b = 0, 0001b = 1, 0010b = 2, 0011b = 3, and so on until 1111b = 15.
If one adds 15 to 15, the resulting number is 30. The corresponding binary number is 11110b. That is 14 plus 16, or 1110b plus 10000b.
In other words, the carry flag here means the number 16, 2 to the fifth power. The SN74HC283N adder considers the presence of a carry flag at the input and outputs a carry flag to the output, which is why it is called a full adder.
So, we have a microchip with two inputs for four-bit binary numbers: A3..A0 and B3..B0.
Why does binary digit numbering start with zero? The digit's index is the power to the base; in our case, the base is 2.
0100b = 4 - 2 to the second power. 1000b = 8 - 2 to the third power. 1001b equals 2 to the third power plus two to the zero power, 8 + 1 = 9.
Any number to the zero power is equal to 1.
The microchip has a four-digit sum output S0..S3 and a carry flag output. It also has overflow input, but we won't use it, so we'll simply ground it. Thus, this input will always be a logical zero.
What can we do with the adder? We can add two binary numbers and receive their sum. We have a carry flag that indicates whether the adder has overflowed. We can add a binary number to 0 by entering 0000b (simply four 0 bits) into one of the inputs. The output will be the same number. You'll see in a moment how this is useful.
So, we've already got ourselves an ALU—not that capable, but enough for us to use. Next, the processor needs registers.
Registers are internal memory cells of the processor meant for direct access. From these exact registers, four-bit numbers arrive at the inputs of the ALU, and the resulting sum is written to them.
The register is based on a synchronous latch. Our asynchronous adder does not save data; its output momentarily pulls its pins low or high, corresponding to the input values.
(To be more precise, it happens almost instantly, but the performance of the SN74HC283N chip is so much greater than the clock frequency of our processor that we can ignore this "almost" part.)
Unlike the asynchronous adder, our synchronous flip-flop changes the state of its outputs only when it receives a clock pulse and is subject to "enable" signals at its control inputs. It will keep its state until the signals at the control inputs are permissive and a new clock pulse arrives.
We use a total of four identical 4-bit SN74HC161N registers in our processor. Strictly speaking, they are not just registers but much more sophisticated multifunctional chips—synchronous binary counters.
The SN74HC161N chip has a 4-bit input P0..P3 and a 4-bit output Q0..Q3, a carry flag output, a CLK clock input, and four control inputs.
The inverting asynchronous reset input ¬RST sets all 4 latches to zero whenever this input is driven low, regardless of the state of all other inputs.
A low level on the inverting parallel enables input ¬PE...
Sometimes, a case exists for using multiple computers from a single desk. Several servers could be quietly grinding numbers in the background until they need to be accessed by the user for configuration or maintenance.
Sure, buying several sets of keyboards and mice is always easier. Still, it's smarter to use a specially designed unit, a KVM switch like the one we have here, the INRIKS SW4041KVM.
Features
INRIKS SW4041KVM is a 4-to-1 HDMI KVM switch. That means one can connect 4 PCs (HDMI outputs and USB ports) and one set of monitor and USB HID devices like a mouse and keyboard for the user.
This user (should we call him "operator"?) can switch from one PC to another with an IR remote or a button on the unit. This selects what computer is connected to the operator's monitor and peripherals.
In addition to these controls, there's RS232 for connecting to an external control system like Crestron.
The maximum resolution for an HDMI signal is 4K at 60 Hz.
Visual overview
INRIKS SW4041KVM is shipped in a simple cardboard box with a brief description on a sticker. The switch is carefully placed in a plastic tray, and all the accessories are under it.
The box contains:
- HDMI KVM switch
- Power supply: 5V/1A
- User manual
- IR remote
- Mounting ears and screws, 1 kit
- Grounding screw
- Terminal block for RS232
- USB A to B cables, 4 pcs
The device kit is very complete by today's standards. It includes nearly everything needed, even four USB cables. The only exception is the HDMI cable, which has to be bought separately.
The back panel has the following connection ports:
- power input, 5V
- RS232 terminal block connection
- 4 groups for PC connections, each with an HDMI input and a USB-B port
- HDMI output for the operator
- 2 USB-A ports for keyboard and mouse
Front panel
- 2 USB-A ports, just in case you need them
- IR window for the remote
- LED indicators for active input connection
- button to cycle between those inputs
- power LED
The RS-232 port allows the switch to be connected to various control systems to automate processes. The included manual has all the commands for controlling the switch from an external automation controller. Everything is clearly listed, along with the connection parameters needed.
A complete mounting kit with 2 brackets and 6 screws is also included. Those brackets are installed flush with the bottom panel of the case and are useful for mounting on a flat surface.
It is worth mentioning that the case is made of steel, and there is a grounding screw, among other accessories. So the unit can be safely installed in a server rack.
We've found that the paint is scuffed around the mounting point inside the case. This should be done intentionally to provide a better case-to-ground connection. Still, it is rather odd to do the paint scuffing manually.
Disassembling the case, we found it thick, substantial, and solid. Port cutouts are exactly where they need to be, with no shifts or bends.
Looking closely at the PCB inside, there's nothing interesting there. Everything is soldered neatly and accurately. There are a few sloppy spots on the backside, but nothing to worry about. I'm just mentioning those to be somewhat fair.
Testing
To test the INRIKS SW4041KVM switch, we prepared a set of three laptops, a monitor, a keyboard, and a mouse.
Everything's connected, and we have an image on our screen a couple seconds after powering up the switch. The mouse moves as it should; there is no input lag or video distortion. That is exactly the point of this device; one can't tell if there's an active device between the desk and the computer.
We've tried to switch inputs with the button and the remote. The only difference is that you can pick any channel with the remote, and the "SWITCH" button just cycles through them (1, 2, 3, 4, 1, 2, 3,...)
When switching inputs, there's a few seconds of delay. That is for connecting your monitor to the next PC and syncing USB devices. This behavior is normal and should...
Unlike bridges, which can be used to measure the distance to the defect along the cable route, pulser fault locators search for the cable fault location, i.e., determine where exactly the defect is located. At the same time, cable parameters or temperature do not affect its localization accuracy.
The primary purpose of pulser fault locators is to localize defects in the protective insulating sheath of the cable, due to which the shield and/or conductors are shorted to the ground. The signal from the generator is applied between the defective conductor and the earth to find such locations. As a result, a closed circuit is formed (generator-conductor-defect-soil-generator).
Current flowing in the ground is concentrated in the area of the earth electrode and fault. However, the current flows at different depths along various paths with the lowest resistance between these points. A sensitive voltmeter can detect the potential difference in any area of the ground due to current flow. It is such a device that is used in a pulser fault locator as a receiver. The signal is picked up by two probes located a small distance from each other (usually mounted on an A-frame). The receiver probes are stuck into the ground to reduce transient resistance during signal acquisition.
Depending on the condition of the ground, pulser fault locators detect defects with a resistance of 0.5-2 megohms. For successful localization, it is necessary that as much of the current as possible flows through the fault into the ground and through the ground to the earth electrode. Therefore, the generator should be connected to a high-quality earthing system.
AC voltage or DC voltage pulses are used as the test signal. In the first case, the receiver only measures the signal strength between the two probes (potential difference). In the second case, in addition to the signal strength, the polarity of the signal can also be used to determine the position of the receiver's probes relative to the defect (before or after the fault). But the AC signal also has an attractive feature - it allows you to trace the cable.
In any case, the signal strength is minimized when the probes are positioned strictly above the defect and symmetrical about it: if the fault is located exactly below the probe (midway between the two probes of the A-frame), the signal strength will be zero. It is this fact that is used to localize the defect.
For error-free fault location and refinement of the cable trace, the probes should be placed in a plane perpendicular to the trace and again find the point where the signal will be minimized - accuracy can be as low as 0.1 meters.
The signal levels are maximized at these locations since the current is concentrated near the earth electrode and the defect. If the distance between the earth electrode and the fault is large, the signal may not be detected because it is too weak. The distance to the defect should be estimated using a bridge or TDR to reduce the search time beforehand. This will allow you to start the search close to the fault instead of walking along the trace from its beginning.
It is essential to remember that the signal's amplitude at a certain distance from the earth electrode is equal to the amplitude at the same distance from the defect. This can significantly accelerate the search - using a receiver calibrated in this way allows not to react to minor signal fluctuations on the trace. Using a point located on the other side of the earth electrode at the same distance from the cable as the earth electrode as a reference is usually recommended.
Suppose any conductors (pipelines, armored cables, etc.) run close to the cable and parallel to it. In that case, the return current, choosing the path of least resistance, will flow through them rather than through the ground. This significantly reduces the signal level and makes it difficult to localize the defect.
The same problem occurs if the localizable defect is located in one of several...
Welcome to my guitar effects workshop! Today, we will study the circuit and history of the pedal, which is copied and improved by dozens, if not hundreds of companies and masters. And, of course, we will build and listen to our own copy.
Almost every audio signal processing effect in electric guitar music and analog synthesis was born from faulty equipment or setup.
I believe the fuzz effect's history began the same day the history of rock 'n' roll began. In 1951, five years before he met his future wife and vocalist Tina, Ike Turner, founder of The Kings Of Rhythm, recorded a song named after an Oldsmobile 88.
More precisely, in honor of the innovative Rocket 88 engine installed on this luxurious, stylish muscle car.
Before recording, the Fender Bassman amplifier Ike was using was dropped, and a tube exploded.
So, instead of a pure bluesy guitar sound, the buzzing sound of the future came out of the speakers. The ensemble played rhythm and blues, but rock and roll sounded.
In 1961, virtuoso session musician and unusual guitar enthusiast Grady Martin recorded the bass solo for Marty Robbins's song Don't Worry through the channel of a tube mixing console that turned out to be faulty. However, not only did this not spoil the solo, which was left on the record and made it onto vinyl, but it was the beginning of a new guitar sound.
To repeat this sound, Orville "Red" Rhodes, known for his iconic Velvet Hamer pickups, created the first custom effect in a box plugged between the guitar and the amp input. Pedal-style effect boxes were invented later.
In 1962, the great Nokie Edwards, whom the Japanese call the King of Guitars, specifically used the fuzz "box" for the first time, the very one created by Red Rhodes, when recording a guitar riff. It was the single The 2000 Pound Bee by The Ventures.
Be sure to listen to this masterpiece song. The fuzz gives the composition a unique space. Each note of the guitar flashes like a firework spark.
Next up. Who hasn't heard (I Can't Get No) Satisfaction by The Rolling Stones? In this song, Keith Richards used the first commercial Gibson/Norlin Maestro FZ-1 Fuzz-Tone, released already in a pedal body.
And the much more famous smiling, round-faced Dallas-Arbiter Fuzz Face is, of course, associated with Jimi Hendrix, the virtuoso who took the art of electric guitar playing to a whole new level.
And finally, David Gilmour used the Electro Harmonix Big Muff in his masterpiece solo Comfortably Numb. This is the very pedal we are going to study and assemble today.
But first things first.
In 1967, Mike Matthews, a young IBM computer sales manager, electronic engineer, and musician and producer who had worked with Chuck Berry, among others, was impressed by the song Satisfaction, played on the radio even more often than it is now. The demand for fuzz pedals was great, and they were assembled in New York City by a single music equipment repair engineer, William Berko, in his shop, ABCO Sound, on 48th Street, in single copies.
Bill suggested that Mike work together, and every couple of weeks, they handed Alfred Dronge, the founder of Guild Guitar Company, a few hundred assembled pedals that went by the name Foxey Lady.
These were Mosrite Fuzzrite pedals based on the Gibson Fuzz-Tone circuit. It differs from Fuzz Face in that the second knob does not control negative feedback, i.e., gain. Still, it is a crossfader between the signals from the first and second transistors.
In other words, the knob mixes the amplified clean signal of the guitar with the distorted signal after limiting. It allows the musician to find the right balance between them. Another iconic pedal, the Klon Centaur, works similarly.
Note that the first transistor is a buffer in the original Maestro FZ-1 Fuzz-Tone. It is included in the emitter follower circuit and completely repeats the shape and voltage of the input signal. The foot switch short-circuits the output of the distorted signal.
This is simple, effective, and guaranteed to eliminate distortion...
1. Our equipment fully* supports** the HDMI standard***
HDMI is the most basic standard for digital video transmission.
"Acceptable" quality is HDMI 1.4, "good" quality is HDMI 2.0. All standards above 2.0 are redundant, at least for now. Also, HDMI at a lower quality than Display Port wins in reliability, which is why professional equipment uses HDMI. By 2016, 100% of new TVs with resolutions higher than HD had an HDMI connector.
The HDMI 2.0 standard has many parameters:
- Resolution, 4K@60 or 5K@30 or 8K@30 (4:2:0)
- HDR support for 1080p@60, 4K60 (4:2:0)
- Widescreen aspect ratios 21:9, 2:1
- CEC, unified control signal
- Audio, up to 768kHz, 24-bit, 32 channels
- 3D
- Ethernet
🧐 In practice, compliance with the HDMI 2.0 standard is guaranteed to mean: 4K resolution at 60 frames and 4:2:0 color subsampling; audio up to 192 kHz 24-bit 2 channels. All other parameters are optional, but these two are sufficient for professional use.
Good HDMI equipment manufacturers list all supported parameters and all technologies in the specifications to avoid surprises during installation.
HDR - high dynamic range. This technology allows the display to increase brightness locally. HDR is often used in bright night scenes in movies or when the sun, fire, or explosion is shown on the screen.
In technical terms, HDR is a wider color range, extra bits for extra brightness. Color is 8 bits; a signal with HDR requires 10 or 12 bits. Most budget segment custom displays use a conversion: it takes HDR 10 bits and converts it to 8.
To support extended dynamic range, all elements of the system must work with it:
- A source, computer, or media player with HDR support at the output end
- The content, video file, or web player must contain HDR information
- Cables, extenders must transmit 10-12 color bits
- Display with 10–12-bit HDR support; specific HDMI port on the display must support this mode
- The display must have a peak brightness many times higher than the nominal value; this is the point of HDR technology.
🧐 The "HDR-compatible" label on the equipment does not mean that it supports this standard. It's a marketing ploy, meaning the device takes an HDR signal as input and quietly converts it to regular 8 bits. The source sends HDR, but the HDR-compatible device simply ignores the extra 2 bits of brightness.
🧐 HDR 10 bit (8bit + FRC) is also an example of a marketing ploy. The sentence has a cherished number 10, but it stands for "8 + FRC". FRC stands for Frame Rate Control, meaning that the monitor receives a 10-bit HDR signal and plays back 8 bits digitally enhanced. The effect is like HDR, suitable for inexpensive TVs, but is not HDR.
Good manufacturers do not specify HDR support for equipment where it is emulated or limited to compatibility only. Therefore, the choice of HDMI devices with HDR support is quite narrow.
3. Our extenders transmit the video signal* without delay**
Video signal transmission is always delayed. A 0 ms transmission delay is physically impossible, but it is unnecessary in practice. During transmission, time is lost to encoding/decoding in the extender.
Human reaction time is on the order of 250 ms, and reaction time of cyber athletes reaches 100-120 ms. The minimum perceived latency a human can hear and see is 15-30 ms.
The monitor and the extender give the delay or input lag from the computer or set-top box to the monitor. Consumer segment monitor introduces 30-70 ms of delay; gamer and professional models are closer to 10-30 ms.
🧐 A "latency-free" HDMI extender is a device that transmits a signal faster than 30ms. The main consumer quality of lag-free video transmission is the ability to work comfortably with a mouse or trackpad. For this purpose, it is enough to keep the transmission speed within some known limits.
Where manufacturers specify "latency free", it is there. Still, it is less than all other...
The interpretation of the measurement results should be discussed in particular. What should be done after the cable fault location has been searched and the distance to the defect has been measured? First, it is necessary to find the scheme where the cable route is indicated and to estimate approximately which section of the cable the localized defect is located. It is required to make clarifying measurements from the switching points closer to the defect. Other measuring devices, e.g., TDR, should verify the results. Then it is necessary to measure a known distance to the defect on the cable route. It is most convenient to use measuring wheels for this purpose. However, the cable is not laid strictly along the line, so the defect may be quite far away from the postponed point. That is why before searching for the place with a defect on the cable, it is necessary to find the closest switching point to it and measure the defect from it.
Another group of "secrets" is related to the defect localization on real cables, which always consists of several sections. The section parameters may differ, e.g., regarding cross-section (which affects DC measurements) or cable type (which affects AC measurements). This is another reason you should measure as close as possible to the fault to be detected.
For composite cables
The rules to be followed when performing measurements on composite cables and DC are simple (see the following two figures). In cases where the faults to be localized are caused by low insulation resistance of the conductors (short circuits of the conductors to the shield or to each other). The same rules apply to AC measurements when localizing faults caused by increased core resistance (breaks).
For cable branches
A separate case is the fault localization in cables with taps. The general rule to avoid errors is that measurements should be carried out on individual cable segments. In cases where this is impossible, they are carried out on the cable with branches. But always keep in mind that the result depends on the choice of the location of the strap. Suppose the measurements indicate that the defect is located at the switching point. In that case, it may also mean that the branch cable is connected to the cable where the defect is located. It can be localized by disconnecting the branch, taking measurements, or changing the strap position.
The figure above shows that if there is a defect in an undocumented tap, the fault location may be misleading - it will look like the problem is at the tap connection point. And the measurements on both sides will give the same result. In such a case, only an OTDR, where the tap will be visible, or cable examination at the switching point will help to finally determine the location of the defect.
When an AC measurement is used to locate a wire break, the presence of an undocumented tap will also lead to erroneous results, but in a much less predictable manner. If the tap is located upstream of the open circuit, it will introduce an unknown added capacitance. The actual distance will therefore be less than the measured distance.
When localizing a break on a line with taps, it is also necessary to make two measurements according to the diagram shown in the figure below. One measurement is made with an AC bridge, and the other with a DC bridge.
Of course, these rules can only be followed if there is documentation of the cable network where the defect is localized. Therefore, when the first serious fault is eliminated, carefully prepared documentation will more than compensate for the time and resources spent on its creation.
Accepted designations
In most cable fault locators, the following intuitive and convenient symbols are used to designate the lengths of the various cable sections with localizable faults, which were chosen for the figures in this article:
DTS = Distance To Strap (distance from the device connection point to the installation point of the jumper at the far end);...
Earlier in the article (link), we reviewed the long-distance transmission of HDMI and USB signals over twisted pair cable. We explained the difference between HDMI USB 2.0 and HDMI KVM extenders in terms of practical application.
But what if you only need to extend a USB 2.0 interface over a long distance via twisted pair cable? What to do to remotely connect a webcam, speakerphone, or other equipment?
Let's look at such extender type using INRIKS EX100USB USB 2.0 extender as an example.
Brief feature description
The INRIKS EX100USB Extender is a twisted pair USB transmitter and receiver kit. Using CAT6 cable, a transmission distance of up to 490 feet can be achieved. If CAT5e cable is used, up to 330 feet.
The extender provides USB 2.0 transmission with a High-Speed (480Mbps) maximum transmission speed.
The transmitter must be connected to a signal source (PC, laptop, DVR, and the like). The receiver has four USB ports for connecting various devices.
A unique feature of the INRIKS EX100USB kit is the ability to work in two modes: one-to-one connection and switch relay.
One-to-one connection connects the transmitter to the receiver with a single piece of twisted-pair cable up to 490 feet.
Switch relay connects the transmitter to the receiver through a gigabit switch. This scheme will increase the transmission range to "490 + Switch + 490" feet.
External checkup
The extender is supplied in a standard cardboard box. The label shows the main kit features.
After opening the box, you can see the transmitter and receiver in the blister. The power adapter, USB cable, and manual are under the blister.
The transmitter and receiver are compact in size; this is an advantage. The housing is made of metal and looks good.
A minimum port set can be found on the transmitter. These are USBs for connection to a PC or laptop. And also RJ45 for twisted pair connection.
The receiver has an RJ45 twisted pair port, four USB connectors for connecting peripherals, and a power adapter connector. Because of this, we assume that the transmitter is sufficiently powered by the laptop's USB power supply.
When we disassembled the case, we found that all the components fit perfectly. Why do we pay attention to this? In our practice, we have studied the extenders of other manufacturers with large gaps between the case and connectors. We had an impression that the extender manufacturer bought a certain universal case and tried to produce their components (boards) for this case. The final version looked very shabby. In the case of INRIKS EX100USB, we believe all parts were developed by one manufacturer.
Removing the top cover, we once again made sure that the components were assembled with high quality. The board is fixed in four points, which eliminates backlash.
If we have no claims to the front side of the board, the back side has some minor defects. We do not think that these defects will affect the performance. But visually, it looks strange.
Performance testing
To test INRIKS EX100USB, we prepared a laptop, webcam, speakerphone, keyboard, mouse, and CAT6 twisted pair cables of different lengths.
One-to-one connection
We connected our equipment according to the diagram in the instructions:
We took 490 feet of CAT6 cable to connect the transmitter and receiver. After powering up, we found no power indicator on the receiver and transmitter. The only indicator is the LEDs on the RJ45 connector, which start flashing when the devices are connected to each other.
Next, we connected the webcam, speakerphone, keyboard, and mouse to the receiver. After a typical pause, all devices were detected in the laptop's operating system. We didn't feel any delay in keyboard and mouse operation. Then we made a test video call. Everything worked without any problems. We did not feel the peripheral devices were connected via a twisted-pair USB extender.
Switch relay connection
In the next step, we tested the possibility of extending the range with an Ethernet Switch....
AC measurements are useful for localizing core breaks. This is best accomplished for shielded cables by measuring each core's capacitance relative to the shield. Knowing the core capacitance C-linear, the length of the broken core can be calculated using the formula: Lpaire = Ccore-shield/C per length
When measuring a broken circuit's core capacitance, the cores of the other circuits in the cable bundle are connected to each other and to a reliably grounded shield. If the capacitance measurement results of both cores are the same, they are broken in the same place. Different values indicate a break in only one core and in the one with the lower capacitance. The distance to the breakage point is calculated by the formula Lpaire = Ccore-shield/C per length, where Ccore-shield and C per length are the measured and the linear capacitance of the core.
It's crucial to remember. Defects in the cable shield have a significant influence on the measurement result. With the help of the above scheme, it is possible to determine the cable screen breakage place. For this purpose, the screen is disconnected from the grounding. Its capacitance relative to the ground is measured on both sides. The breakage place is calculated based on the ratio of the results of these measurements and the cable length (if it is unknown, it is necessary to use measurements for any pair of cores at constant current). The distance to the break is determined approximately - based on the measured capacitance of the shield and its capacitance (it is estimated as 0.083 of the core capacitance relative to the shield).
If the cable is not shielded, the distance to the break can be determined by measuring conductor pair capacitance. However, the Wheatstone bridge circuit does not provide sufficient accuracy. However, even in the case of DC measurements, the Wheatstone scheme is rarely used for fault location.
The Murray Bridge is often preferred because it allows measuring resistance differences between two arms. Thus, for example, the asymmetry at direct current is measured, which is evaluated by the relative value of the resistance difference between the conductors. From the figure, it can be clearly seen that this will be determined using the Murray Bridge. The twisted pair asymmetry at alternating current is measured in the same way.
The same property of the Murray Bridge is also used to localize several other faults. The most common are low insulation resistance, and one of the cores shorted. During measurements, the unknown values of the defect resistance RF and shield resistance Rshield are included in both arms of the bridge, so they are mutually compensated, and their value does not play a role.
At alternating current, the location of a break in one of the pair conductors can be localized with the Murray Bridge much more accurately than the Wheatstone Bridge. Moreover, in this case, the information about the cable core capacitance is not needed - the ratio of capacitances C1 and C2 will indicate the ratio of the distance to the defect to the length of the entire pair.
The measurement scheme for localization of the place with low insulation resistance between the conductors of one pair is more complicated. Here too, the compensation effect of unknown values is used.
In all DC measurement schemes for Murray Bridge, an additional conductor is used in addition to the core with the defect to be localized. It can only be a core of the same pair or one of the free pairs in the same cable because it is essential that the RDTS (resistance of the additional core) is equal to the sum of the resistances RDTF+RSTF for the defective core. Since there is always the possibility of a defect in one core due to poor contact at the splice point of two cable sections, one can only be partially sure of the measurement accuracy.
The Hilborn/Graf Bridge measurement circuit can overcome this drawback. As can be seen from the figure, although the circuit is based on two additional conductors,...
HDMI twisted pair HDMI extenders are commonly used to extend the HDMI interface over long distances. This is a kit of transmitter and receiver that are connected to each other with twisted pair cable. Many manufacturers have the same design.
But what if you need to transmit an HDMI signal and a USB signal? There are many devices for such cases. They are called HDMI KVM or HDMI USB twisted pair extenders. Both device types have HDMI in/out and USB ports on the body. But the functionality, purpose, and price of these devices are different. Let's take a look at these differences.
HDMI KVM extenders
This is the most mass type of active extenders, which can transmit not only HDMI signal over twisted pair but also USB. We need to know that in this case, USB is used only for keyboard and mouse connection; that's why this extender type is called HDMI KVM. Where KVM stands for keyboard, video, and mouse (a common term).
Manufacturers so indicate to buyers that it is possible to connect a video device to their extenders for HDMI transmission, as well as a USB keyboard and USB mouse. The reason is the low speed of USB signal transmission. Manufacturers rarely display the supported USB version in the specifications. We assume that it is USB 1.1.
HDMI USB extenders
This is a less mass-produced extender type; in their specifications, you can see the USB version, which is usually 2.0, and it's a more universal extender type. You can connect flash drives, webcams, and USB headsets to such a device. But it is also a more expensive type of extender. If you only need to remotely connect a TV, keyboard, and mouse, you can limit yourself to buying an HDMI KVM extender.
Let's look at the first device type using the INRIKS EX2072KVM HDMI KVM extender as an example.
Main features INRIKS EX2072KVM
The INRIKS EX2072KVM is a twisted pair HDMI KVM transmitter and receiver kit that allows you to extend HDMI, USB keyboard, and USB mouse interfaces. The kit can transmit 1080p60Hz video up to 230 feet and 4K30Hz video up to 130 feet. The manufacturer does not specify the supported version of the USB port.
The manufacturer positions this kit as a basic one in the lineup of HDMI KVM extenders.
INRIKS EX2072KVM External checkup
Like most INRIKS equipment, the reviewed kit comes in a small cardboard box. You can find the transmitter, receiver, and manual in the blister top part.
The USB connection cable for connecting the transmitter to the controlled device (PC, DVR, etc.) and power adapters for the transmitter and receiver are under the blister.
The transmitter and receiver have small dimensions. Probably the most compact kit in the whole range of INRIKS HDMI KVM extenders.
HDMI, USB, and power connectors are very well matched to the cutouts on the case. Everything looks monolithic and reliable.
You can find the necessary HDMI, RJ45, USB, power adapter connectors, RESET button, and LED status indicators on the front and back sides.
The kit doesn't have removable brackets, which again indicates its position in INRIKS' HDMI KVM lineup.
The device's housing is made of thin metal. No, it's not flimsy and doesn't easily bend in your hands. In this case, we compare the metal thickness with the housings of senior INRIKS models.
Soldering is performed qualitatively without visible defects.
Performance testing
In the first step, we use 230 feet of CAT6 twisted pair, laptop, display, USB keyboard, and mouse to test the operation. After connecting the equipment, the remote display showed an image, and we could remotely control the laptop with the keyboard and mouse.
Video transfer and keyboard and mouse control are seamless. The average user will not feel the 230 feet of distance between him and his computer and a kit of accessories.
In the second step, we replaced the keyboard and mouse with a USB headset. The wonder did not happen. The headset repeatedly tried to connect to the computer through the tested extender. But the process continued. We...
An electronic clock without a microcontroller is a circuitry masterpiece that can be looked at forever! Today we continue to explore the practical possibilities of pure logic.
We start with an hourglass on the shift registers. Look what a beautiful design in a two-board stack! The top board has only the LEDs, and the bottom has all the chips and other components.
Any digital circuit starts with a clock. Instead of the apparent 555 timer solution, the circuit designers used the CD4069. It contains six logic inverters, of which only two are used, and the other four are idle.
The generator works as follows. There is almost no current through the U1 pin 1 and 3 because they are high-impedance inputs, almost like an operational amplifier. To make input 1 even more high-impedance and thus negate the effect of its current, the developers added a resistor R31.
The time-setting circuit, consisting of capacitor C1, resistor R32, and trimmer VR1, is constantly overcharged. Because it is connected between the input and output of the inverter U1B. More precisely, the capacitor is recharged through the series-connected resistors.
And an inverter is an inverter so that the logic level on its output is the opposite of the level on the input: one if the input is zero, and vice versa, zero when the input is one.
Ask, how is the capacitor recharged between the output and the input of the inverter? Did we just write that there is practically no current through the input? - Exactly right, but the current goes through the output U1A - the second pin of the chip.
When logic 0 is on pin 1, logic 1 will be on pin 2 and, therefore, on pin 3. And on pin 4 will be a logical 0. So the plus pin of C1 will be on the circuit's ground, and the minus pin will be charged through the resistors to the plus of the power supply.
That is precisely right. This is bad and wrong for an oxide electrolytic capacitor, and a solid device would have put a non-polar capacitor in C1's place. But in this toy, the developers decided that this would do.
Personally, my hourglass hasn't failed yet, but I don't turn it on for a long time. And if the capacitor still goes terribly, I will replace it with a non-polar one. The microcircuit won't burn out from the capacitor breakdown because it is charged and discharged through resistors. The clock generator will stop working, and accordingly, the sand in the LED lights will stop falling.
As soon as the capacitor is so charged, its minus terminal, connected through resistor R31 to input U1A, shows a logical 1, the second, and, therefore, the third pin of the chip will switch to low and the fourth to high.
The capacitor will start to charge in its correct polarity (while restoring the parts of the aluminum oxide layer that are corrupted by the wrong polarity) until pin 1 receives a logical 0, and everything repeats.
The time of this process, and therefore the clock frequency of the circuit, depends on what resistance the trimmer is set to. The limiting resistor R32 does not allow make the circuit resistance to zero.
The remaining LED control circuit consists of four identical nodes, each on a 4-bit shift register. One CD4015 chip contains two such registers. In total, two such chips are used.
The static shift register has a serial input and a parallel output. This means you can enter data - logical zeros and ones - in series on one wire leading to the D - Data input.
And this logic level will go from input D to output Q1, from Q1 to Q2, from Q2 to Q3, and from Q3 to Q4 when a clocking or synchronizing pulse comes to input CP.
Thanks to this memory circuit, you can light and extinguish almost any number of LEDs using just two pins of the microcontroller or just two wires or two radio control frequencies. Instead of LEDs, there can be relays, vehicle model servos, or something else just as enjoyable.
In the case of LEDs or light bulbs, this circuitry solution is called serial bus-driven static indication. It has long been successfully...
When servicing metal cable lines, measuring bridges are most commonly used. However, other devices are also available for locating cable faults.
Firstly, they provide high accuracy in a wide range of measured values.
Secondly, their use makes it possible to organize measurements in such a way as to compensate for extraneous influences, which is indispensable for fault location.
Thirdly, they are not expensive.
It will be helpful for the reader to become familiar not only with the construction of measuring bridges but also with the principles of their application for fault location. However, speaking the language of mathematics, such knowledge is necessary, but more is needed for constructing optimal measurement schemes. Diagnostics is always both an experience and an art.
Pic. 1 The connection of a bridge circuit The principle of the bridge measuring circuit is shown in Pic. 1, and its application in practice is shown in Pic. 2. Resistance R1 is calculated based on the ratio R4/R3 obtained when balancing the bridge, and a resistor with a known value is used as R2. Of course, this gives only the most general idea of the measuring circuit of the bridge. In fact, it is much more complicated - modern bridges are based on digital processors. The microprocessor core allows automating the measurement procedure (in the first models, the operator had to use a calculator, today all calculations are performed by the hardware) to ensure the multifunctionality of the device (many bridges are integrated with other measuring instruments - multimeters, OTDRs, etc.), to eliminate interferences (foreign DC and AC voltages are almost always present on the cores of cables), to organize further processing of accumulated measurements (storage, exchange with the computer, printing and so on). Pic. 2 Bridge circuit in use
The bridge used for the resistance measurement discussed above is named Wheatstone. It uses only two terminals (B and C) to connect the circuits to be measured. Two other bridges, Murray and Kupfmuller, have more advanced circuits. Here the measured circuits are connected with three terminals (A, B, and C). The more complicated Hilborn/Graf schemes use four terminals (A, B, B' and C). Pic. 3. The meaning of increasing the number of connection points will become apparent when considering measurement schemes using bridges. Pic. 3 Hilborn/Graf Bridge circuit in use
All described bridge circuits are used for measurements at direct current (values of active resistances connected to the terminals are determined). In addition, Wheatstone and Murray bridge circuits are used for measurements at alternating current (the values of capacitances connected to the terminals are determined). In such bridges, the voltage source is a sinusoidal voltage generator. Pic. 4 AC Bridge circuit in use
Now let's focus on the measurement schemes. Using the Wheatstone bridge at constant current, measure the resistance of the twisted pair (cable harness), the insulation resistance of the cores of the pair, and the insulation resistance between the cores and the shield ( Pic. 5, Pic. 6, Pic. 7). The values of the mentioned parameters are used to diagnose cable lines. Localization of faults requires the location of the fault on the cable line. Using a DC bridge, it is easy to calculate the distance to the fault location. Knowing the loop resistance Rwire and the cable core resistance R', you can use the formula: Lline = Rwire / 2 R' and calculate the length of the twisted pair. Pic. 5 Measuring the resistance of a cable harness
Their cross-section determines the linear resistance of copper cores in a tabular method. It depends not only on the cross-section but also on their temperature. To avoid errors, you must use the resistance value for the corresponding temperature (it is crucial for overhead cable lines, where the temperature varies over a wide range). In simple bridges, the operator manually enters the values from tables. In more complex devices, an automatic or...Read more
Nowadays, electronic DIY projects with microcontrollers, especially Arduino, are very popular. The microcontroller makes it easy to create many interesting and useful things.
I am even more interested in assembling different devices with simple logic circuits. They are easier to buy when there is a shortage of semiconductors, and they are not susceptible to software failures, hacking, and firmware corruption. And most importantly, their principle of operation is more visual, which gives me aesthetic pleasure.
Today I will introduce readers to four simple devices. Three of them are based on flip-flops, and the fourth one, which we will start with, could use a flip-flop.
Voting machine
The majority rule applies when people vote to accept or reject a proposal. The decision is made if more than half of the participants vote in favor.
If there are three voting participants, it requires two or all three to press the buttons to answer in the affirmative. This is the logic of this little electronic toy.
The 74LS08 chip contains four AND logic elements with two inputs. The output of each element will be 1 if 1 at both inputs. Otherwise, it will be 0.
The circuit uses three of four 74LS08 elements. The inputs of each one are connected to one of three possible pairs of buttons. They are pulled up to the ground with resistors, so the input will be a logical 0 unless the button that connects the input to plus power is pressed.
The CD4075 chip contains three OR logic elements with three inputs. The element's output will be a logical 1 if there is a 1 on at least one of the inputs or two or all three.
If any button pair is pressed, one of the inputs of the 74LS08 will be a logical 1, and the output will be a 1. The transistor will open, the buzzer will sound, and the LED will light.
In the case of an actual voting machine, it would be desirable to lock the button so that the voter does not have to hold it down. For this purpose, lockable buttons or toggle switches could be used.
Or you could use flip-flops - devices with two stable states that remember their state until a signal comes that changes this state.
Standby light with touch switch
But first, let's study a monostable multivibrator, aka a single vibrator. This device has one steady state, which exits under the action of the input signal, gives a certain pulse duration to the output, and returns to the steady state again.
This property can organize lighting in some small room or cabinet. The economical red LED consumes very little current and indicates the sensor location.
If you touch the sensor, the red LED turn off, but the five bright white LEDs turn on. Depending on the adjustment resistor, they will shine for a few seconds to a minute or two. After that, the white LEDs turn off, and the red LED turns on again.
The basis of this circuit is one of the most popular chips among DIY enthusiasts - the NE555 integrated timer.
The two main components of the NE555 timer are an RS flip-flop and two comparators. The comparator is essentially an operational amplifier, or rather an operational amplifier workmode.
When the voltage on the "+" input is higher than on the "-" input, the comparator output will have a high voltage level, i.e., almost plus power. And if, on the contrary, the "-" input voltage is higher than the "+" input, the output will be low - almost minus power. That is practically zero/ground because our power supply is unipolar.
The RS-flip-flop is a circuit with two steady states, a logical 1 and 0 at the output. The one on the S - Set input switches the output to a high state, and the one on the R - Reset input switches the output to a low state. Thus the flip-flop is a memory cell.
The NE555 timer inputs are high impedance, which allows you to connect touch buttons directly to them. A touch button is a metal plate, or a metalized surface on the board, as in our case, where you can touch it with your finger.
The touch of a finger on our sensor connects the capacitance...
The ARC (Audio Return Channel) function in HDMI has helped to remove unnecessary communication between TV and AV receiver, soundbar, or home theater. What does the ARC feature mean for twisted-pair HDMI extenders, and how can you use it?
We will review the INRIKS EX4076E twisted-pair HDMI extender with ARC function (and other useful features).
Main Features
The INRIKS EX4076E extender provides a maximum 4K60Hz video transmission range of up to 230 feet over the CAT6 twisted pair.
The transmitter has an additional HDMI pass-through output for connecting a local TV. The receiver has a S/PDIF digital optical audio output.
The kit provides two-way IR signal transmission to control a remote TV on the transmitter side or a video source (e.g., TV receiver) on the primary TV side.
External review
The INRIKS EX4076E is shipped in a plain gray box. The pictograms on the label show the device's main features.
Inside the box are the transmitter, receiver, and manual. The transmitter and receiver are packaged separately in tactile sachets.
Under the top layer are additional accessories: power adapters, brackets, IR emitter, and IR receiver.
The front and back panels of the transmitter and receiver indicate that we have a complex long-range HDMI signal transmitter. This kit gives the installer additional flexibility in connecting additional devices.
The transmitter has a pass-through HDMI output (e.g., connecting a local TV without an additional HDMI splitter). You can read more at this link:
The transmitter and receiver have In and Out inputs for connecting the IR blaster and IR receiver.
But only one pair is included. The manufacturer assumes that you will transmit the IR signal only one way. Another strange thing for us was the massive size of the IR blaster and IR receiver.
Perhaps these accessories have better signal reception and emission characteristics. But it won't be easy if you need to do a covert installation.
An IR blaster and receiver photo of another INRIKS HDMI extender kit is below for comparison.
The good thing is the removable brackets are included. The brackets are made to attach more flexibly to various vertical and horizontal surfaces.
The receiver has a S/PDIF digital optical audio output on one side and a S/PDIF / ARC switch on the other.
The S/PDIF output connects external audio devices with an optical cable (receiver, amplifier, soundbar, etc.).
S/PDIF mode.
The receiver extracts audio from the HDMI signal from the transmitter and sends it to the S/PDIF output.
ARC mode.
The S/PDIF output will return audio from a TV connected to the receiver (if the TV supports the HDMI ARC function).
Myth. Thanks to ARC, the sound from the TV is transmitted over twisted pair towards the transmitter (for some installations, this would be very useful). It is not!
Devices teardown
The receiver has a thick housing with ribs to improve cooling.
The PCB is locked into the case tightly without any gaps. The front side does not have any problems. But the back side has a minor patina at the soldering points.
Testing
We connected the transmitter and receiver with a 230 ft CAT6 twisted pair for the first test. The connecting cables for the laptop and TV were 6 ft long.
The video started streaming to the TV without any glitches immediately after the connection. We replaced the twisted pair cable with a CAT5e 230 ft cable. To our surprise, the video appeared on the TV. The manufacturer specifies a range of 230 feet exactly when using CAT6 cable, and this is very important.
But after some time, the video signal disappeared for a short time when using the CAT5e cable. Therefore, we do not recommend...
In the previous article, we reviewed the basic parameters NEXT and FEXT. The Attenuation to Crosstalk Ratio (ACR) is used when evaluating structured cabling. This parameter is equivalent to the signal/noise parameter concerning the transient effects at the near end of the NEXT, i.e., it serves as an estimate at the receiver input for the undergone line attenuation of the signal and for noise from the transient effects at the near end. Quantitatively, ACR is expressed as a logarithmic measure of the difference between NEXT and cable attenuation. If, for example, the ACR value is 10 dB, this means that the NEXT power of the interference at the receiver input will be 10 times less than the power of the useful signal, i.e., the signal-to-noise ratio will be 10.
Suppose the communication system operates in single-cable mode, and the signal levels at the outputs of the transmitters at points A and B are the same and equal to 0 dB. If the line attenuation at frequency F denotes by Ak, then at transient attenuation NEXT at the same frequency signal levels, Pc and transient noise Pp at the input of receiver A will be Ak and NEXT.
Then ACR = Pc - Pp = NEXT - Ak.
The practical meaning of the ACR parameter becomes more precise if the frequency characteristics of the attenuation of a symmetrical pair (A), transient interference (NEXT), and the parameter (ACR) are presented on the same graph. The frequency at which the values of attenuation and NEXT are the same (in this case, it is 100 MHz) determines the upper limit of the operating frequency range. At frequencies above the boundary value, the power of the interference NEXT exceeds the signal strength.
Another cable system indicator, the Equal Level Far End Crosstalk (ELFEXT), has the same physical meaning as ACR. The only difference is that ACR is associated with NEXT, while ELFEXT is associated with FEXT. The ELFEXT parameter becomes critical when several transmitters of the same system are transmitting in the same direction on pairs located in the same cable.
In this case, ELFEXT = FEXT - Ak.
In addition to the ACR and FEXT parameters, two additional parameters are used - PS-ACR (Power Sum ACR) and PS-ELFEXT (Power Sum ELFEXT), which consider the real influence on this pair of all other cable pairs.
ASYMMETRY (IMBALANCE) LINE
Asymmetry is a transmission parameter, as it is determined by the pair parameters and affects its bandwidth, and an influencing parameter, as it affects the transitions between other pairs.
Each symmetrical line must be balanced concerning the ground in a certain way. Two types of asymmetry are distinguished depending on the current, DC, or AC.
DC asymmetry is estimated by the relative value of the difference of resistance of the cores of a symmetrical line and should not exceed 1%. The presence of the resistive unbalance of the line, equal to the difference of its core resistances measured at AC current, can be interpreted as the inclusion of an additional low-pass filter with the resistance of the longitudinal arm dR. In addition to the resistive component, the longitudinal unbalance of the line in the general case contains a capacitive component; it can arise, for example, due to accidental crossing of the cores of different pairs in the connection points of cables. This component can be interpreted as the transverse capacitance of the additional low-pass filter mentioned above.
The AC Longitudinal asymmetry can be caused by loose contact at cable core joints (twist or splice points, switch cabinets, etc.). The longitudinal unbalance problem cannot be solved, even if the longitudinal asymmetry of the pair in question is reduced to normal. This fact is a necessary but insufficient condition for solving the problem of longitudinal asymmetry in a particular cable. The state of sufficiency requires that all pairs of the bundle or the loop must be checked for compliance with the asymmetry norms. The fact is that any unbalance of even a non-working pair is a source...
I have been interested in smart home systems, automation, and sensors for a long time. I like devices without reference to any manufacturer. So I often use the excellent Shelly Wi-Fi devices. These relays, controllers, and bulbs have an open embedded web server and are controlled via MQTT or web API.
I recently made new lighting in my home lab. I used a Shelly RGBW2 controller (24 volts) for the bright white LED strip (main light) and Shelly Duo RGBW GU10 bulbs (background light).
I immediately noticed discomfort in my eyes, and by evening my eyes were watery. I thought I had pinkeye, or the air in my room was dehydrated, or the street air was suddenly polluted. I agonized for two days.
On the third day, I experimented with LEDs and a spectrometer for one of my future posts. I was getting extraordinary results. During one of the experiments, I pointed the spectrometer at my illuminating LED strip in the lab for comparison with samples. Bingo! I saw a scary pattern of light ripples.
I also measured the light pulsations from the bulbs and saw a similar pattern.
The Shelly RGBW2 controller and Shelly Duo RGBW GU10 bulbs produce 600/1000 Hz pulsations (accordingly) and deep modulation (almost 100%).
But maybe it's normal, and my eyes are abnormally sensitive?
Briefly. «Max % Flicker ≤ Flicker Frequency x 0.08» For a frequency of 600 Hz - the modulation must not exceed 48%. For a frequency of 1000 Hz – the modulation must not exceed 80%. For a frequency of 1250 Hz - the modulation can be any.
My spectrometer detected an amplitude of 98-99%... And that's too bad.
How are the light modulation (amplitude) and the light pulsation frequency related?
For the Shelly RGBW2 controller. For the Shelly Duo RGBW GU10 bulb.
Dependence of pulsing frequency and modulation depth. This is the safe area graph from IEEE 1789-2015. My crossover point (98% at 600 and 1000 Hz) is in the white zone. This means "the product is not acceptable". Controller output voltage modulation for powering the LED strip.
A little check on the other side. I built a small circuit to test the voltage modulation from the controller (Shelly RGBW2 output) to the light source. I connected the device to a 24-volt power supply. I attached a load (a piece of LED strip) and an oscilloscope at the channel's output.
Additionally, I will check several device operating modes: 1%, 50%, and 97% of maximum brightness, and I want to confirm my guesses about the PWM modulator operating mode.
My results. For 1% power:
For 50% power. The main light in my lab works in this mode.
For 97% power.
The minimum PWM regulator voltage is less than 10 volts in all cases.
This is not zero. Could the LED strip emit light at this voltage? If yes, then the light pulsation amplitude (the difference between the minimum and maximum level) may decrease noticeably. Is my spectrometer wrong, and the light emission amplitude does not start from zero?
I assembled another test bench to test the minimum supply voltage for emitting light from the used sample strip. Simple. I connected the LED strip to an adjustable power supply.
At 10 volts, the strip does not work - there is no light emission!
I gradually increased the output voltage and got the initial result (weak glow of the LED strip) at 15.4 volts....
You must connect multiple video sources to a TV with only one HDMI input. Switching the HDMI cable is inconvenient and causes wear and tear on the TV connector and its repair. Instead, your best choice is to buy an HDMI switcher. This device usually has several HDMI inputs and one HDMI output. You can switch sources using the buttons on the front panel or with an IR remote control. Some switchers have an RS-232 port for connecting external control systems.
When looking for an HDMI switch in stores, you may find a more advanced device, the multi-switch, which costs a bit more. What is it? Is it a good buy? Let’s find out.
HDMI switch. General view
What is an HDMI switch, and how does it work, using the INRIKS SW4031 (analog is Lenkeng LKV301-V2.0) as an example? The device has 3 HDMI inputs for connecting video sources (laptop, TV set-top box, video recorder, etc.) and 1 HDMI output for connecting a monitor / TV / projector. The maximum resolution is 4k@60fps.
The device is shipped in a cardboard box. This is the usual packaging of devices for the professional consumer. Mass-market products are often packaged in boxes with colorful prints.
The Switcher has a compact size. The bottom of the package contains the IR remote control, a 5 V power adapter, and instructions.
All connectors are located on one side. This feature simplifies the wiring organization. In addition to the HDMI ports and the input for the 5V power adapter, there is an RS232 port. This is another attribute of professional orientation. The device can be connected to various control systems. For example, to control audio/video complex with one console, touch screen, or for automation (running some scenarios). This extensive theme is better explored in more detail in a separate article.
The status indicators (on/off, active input) and the input switching button are on the front side.
The remote control has a minimum button count.
The case is made from thick metal and feels very monolithic in the hands. The connectors fit very well. The gaps are minimal.
The soldering of elements and connectors is neat.
HDMI switcher. Performance testing
According to the diagram, we connected three laptops and one monitor to the switch.
We found a delay of several seconds when turning on the first input. The same delay is also present when connecting the laptop to the TV directly. It is explained by the two devices matching, which takes time. The picture quality is excellent.
We see the same delay when we switch to the second and third inputs. When switching back to the first input, we see the same delay again, i.e., the matching process happens repeatedly.
This switching is common to all low-cost HDMI switchers. If the long switching time is unacceptable, you should look for a device with Seamless Switching. This function is necessary to switch between cameras during live broadcasts on the Internet.
You can select the desired input or scroll through all video sources individually with the remote control.
The manual contains a port setting description and switching commands for RS232 control:
HDMI multi-viewer switcher. General view
What is a multi-viewer switcher, and how does it work (using INRIKS SW4041MS (analog is Lenkeng LKV401MS) as an example)?
This device has four HDMI inputs for connecting various video sources (TV set-top box, DVR, laptop, etc.) and one HDMI output for connecting a TV. The maximum resolution is 1080p@60fps.
The SW4041MS multi-switch comes in a similar cardboard box as the regular switch. The package contains the multi-switch, a 12V power adapter, a removable surface mount, and instructions.
Unlike the usual switch, the SW4041MS has HDMI and power cable connectors on both sides. Four HDMI inputs are on the rear side. One HDMI and a DC 12V power input are on the front side. The control buttons and the IR receiver are also on the front side.
The packaging box is made of cardboard. A small window allows the user to identify the power supply model without removing it from the packaging.
The power supply is built on the TEA18363 chip.
It is a single-cycle DC-DC converter controller from NXP Semiconductors. The chip needs an external n-channel power transistor. The controller is designed for a flyback converter topology and focuses on maximum power efficiency with minimum components. This feature is listed in the datasheet footer: "TEA18363T GreenChip SMPS control IC".
Structural diagram is traditional: input → filter → rectifier bridge → inverse pass converter with rectifier working for output C-L-C filter, regulation by the output voltage, the control signal is transmitted through the optocoupler.
The power supply has no PFC.
Careful assembly of the components. The quality of the connections is good.
We consider placing the optocoupler, which is practically under the transformer, as a design disadvantage. If this component fails, it won't be easy to replace it.
The manufacturer used the output rectifier diode in the DO-201 package (shown with a red arrow in the photo) for an unclear reason. After all, the design provides for a diode with heat dissipation to the metal wall of the unit.
Test results
• The pulsation value as a fraction means that the voltage has pronounced HF (numerator) and LF (denominator) components. • The hottest component in the power supply is the output rectifier diode. Its temperature is shown in the corresponding table cell. • The overcurrent protection trips at an output current of 2A and operates in start-stop mode.
What is the "start-stop" mode of protection?
When an overload is detected, the power supply turns off, pauses briefly (usually after 0.5-2 seconds), then tries to turn on again; if it still sees an overload, it turns off again and then goes through the cycle until it finds that the load is back to normal at the next start attempt, after which it resumes regular operation. In the event of damage to the load, this mode reduces the risk of fire and energy loss many times over. This is the reason why this mode is actively used in modern power systems. However, it also makes it impossible for several separate power supplies to operate in parallel for a total load greater than the rated load of one of them.
Output voltage pulsations
Slow sweep waveforms
Fast sweep waveforms
The waveforms clearly show that the converter goes into burst mode in no-load mode. The overall ripple level increases due to an emerging low-frequency component with a peak-to-peak of about 40 mVp-p.
Conclusions
• The output diode is in a heavy thermal mode when the housing is closed. The transition-to-environment thermal resistance of the DO-201 package is high, about 86 °F/W, and at an average output current of 1.5 A, this becomes a problem. Clearly, abandoning the stock diode with heat dissipation to the block wall was a bad idea. • The power supply can operate at full load for short periods of a few minutes, but the following limits should be observed for the safe and continuous operation of this power supply: - It is dangerous to operate the unit at a constant full load. At an ambient temperature of 77°F, the output rectifier diode temperature reaches dangerous levels. - A load reduction of up to 70% allows regular unit operation at ambient temperatures up to 86°F. • Power supplies of this type cannot be paralleled to work with a load greater than the rated load of one power supply.
The main influences in symmetrical cables are transient influences at the near and far ends. The influences are caused by parasitic electromagnetic and capacitive coupling between pairs of the same cable or several closely spaced cables. Devices for diagnostics and localizing faults in metallic cables are used to assess such transient influences.
The primary method of reducing such influences is to twist the copper pair strands. The most stringent requirements are structured cabling with a wide range of operating frequencies. For example, no twisting is allowed at a distance of no more than 1/2 inch from the two cable segments' connection point.
A transient influence measure is: - Near End Transient Attenuation (Near End Crosstalk, NEXT) - Far End Transient Attenuation (Far End Crosstalk, FEXT).
These parameters allow you to assess the suitability of symmetric cable pairs for high-speed data transfer. The transient attenuation NEXT and FEXT can be expressed as the logarithm of the ratio of the oscillator power P1 feeding the affected circuit to the interference power P2 in the affected circuit, that is, as 10lg (P1/P2) dB or as the level difference at the specified p1 to p2 points.
You must remember that the signal or noise level at any point X of the link is estimated as px = 10lg (Px/1mW) dB. Here Px is the signal power at point X. The designation dBm is sometimes used in place of the dB designation to emphasize that a signal power of 1 mW has been chosen as the reference power. We will use the abbreviated dB designation below in the text. The NEXT value is the difference between the signal level at the output of the transmitter of one pair and the interference it creates at the input of the receiver of the other, measured at the same point, i.e., NEXT = p10 - p20.
The NEXT parameter is the major one in single-cable communication mode when signals of opposite directions are transported on pairs of the same cable. NEXT also plays a key role when the echo-compensation method separates signals of opposite directions transmitted over one pair.
As you know, the opposite direction signal spectra completely (for example, for HDSL) or partially (for ADSL) coincide. The value of FEXT is estimated by the signal level difference at the one pair's transmitter output and the interference created by it at the other pair's receiver input. However, unlike NEXT, in a FEXT measurement, the affected pair's transmitter and the affected pair's receiver are located at opposite points on the transmission line.
FEXT is the primary parameter in a two-cable link operation when opposite direction signals are transported on different cable pairs. FEXT is also important when the frequency division method of FDM signals (e.g., in ADSL or VDSL systems) separates opposing direction signals transmitted over the same pair. Then the opposite direction transmission signal spectra do not overlap, and there is no transient effect at the near end.
All other things being equal, the value of FEXT is significantly greater than NEXT because, in the first case, the influencing signal undergoes attenuation in the communication line. In contrast, it directly affects the influenced pair in the second case.
The NEXT parameter first decreases with increasing line length L. Then it stabilizes: starting from a certain length, interference currents from distant sections come so attenuated that they have almost no effect on the NEXT value. The situation is different when mutual interference currents are added at the far end - as the line length increases, all of its sections contribute the same interference values. Transient attenuation decreases with increasing frequency, with NEXT decreasing with frequency at a rate of 15 dB per decade and FEXT decreasing at a rate of 20 dB per decade. The smaller steepness of the FEXT frequency dependence is explained by the attenuation of transient interfering currents coming to the near end from distant line sections increases with frequency....
Many guitarists consider the DS-1 to be the worst-sounding guitar pedal. Could this 1978 Roland design be a failure and is now hopelessly outdated?
However, the idol of millions, Kurt Cobain, the author of world-favorite solos John Frusciante, and electric guitar classics Steve Vai and Joe Satriani either did not know that the BOSS DS-1 sounds terrible or managed to make it sound good.
We can get a good sound out of this classic pedal, too. For that, we'll put it, listen to it, and start by studying the circuitry.
Like most other guitar pedals, it is powered by a 9-volt battery. In the case of overdrive and distortion pedals, this battery not only gives you independence from the power supply but, oddly enough, also plays a part in shaping the sound.
Lovers of vintage pedals also prefer vintage, saline-type batteries. The fact is that the Leclanche manganese-zinc cell has not only less capacity and durability but also a higher internal resistance than the more modern alkaline cell.
The high internal resistance of a battery is usually a bad thing. But in the case of guitar amplification, the drawdown of the supply voltage due to the current consumption changes the character of the sound for the better.
After all, the task of a guitar circuit - pedals, amplifier, cabinet with speakers, as opposed to hi-fi equipment - is not to accurately reproduce the input signal but to distort it beautifully. Beautiful, i.e., softened, which is achieved by power sagging.
Mesa Boogie is the world leader in amplifying heavy, overdriven guitar styles. It equipped its flagship product, the Triple Rectifier head, with a rectifier switch: tube and solid-state.
And for the creators and buyers of the amplifier, it was so important that the word Rectifier became the central part of its name! The fact is that different rectifiers have different load characteristics, so they limit the output signal in different ways. And it is necessary to soften it. Otherwise, you will get unpleasant to the ear "sand".
And the miniature, all-semiconductor Spirit of Metal by Hughes & Kettner has not a rectifier switch but an entire SAGGING knob that adjusts to simulate the load response of the power supply.
This adjustment proved so crucial for designers and musicians that one of only four knobs on the front panel was dedicated to it. A second tone knob could have been made, such as an ultra-low resonance or an ultra-high frequency preset, like the Peavey 6505 and many other amplifiers.
Or the opposite, you could make a smooth adjustment from vintage mid boost to modern mid scoop.
In different amplifiers, pedals, and even electronic loads instead of a cabinet, this knob or switch may have different names: CONTOUR, VOICING, SCOOP, SHAPE.
Each adjustment mentioned is extremely useful for shaping the desired guitar sound. However, Mesa Boogie, Hughes & Kettner, KORG, Danelectro, and many other guitar equipment manufacturers have found the power drawdown of tube and transistor amplifiers to be just as effective, if not more so, in coloring the sound.
Knowing this feature of the guitar equipment, you can understand the purpose of the resistor R38 and the diode D3 in the left middle part of the circuit. The pedal is powered directly from the battery and from the power supply through a silicon diode, which draws about 0.7 volts, and a 470-ohm resistor, on which every milliampere of current consumption will cause a draw of as much as 0.47 volts.
And this diode is not a protection diode. The protection diode D1 is in the classic reverse circuit at the bottom left. If you connect the power supply or a 9-volt battery in the wrong polarity, the diode will short out the power and save the rest of the circuit.
A circuit of resistor R38 and diode D3 simulates the load characteristic of a vintage saline battery when powered by a 9-volt adapter. This is the first of the little-known technical secrets of the DS-1 pedal, which is hard to notice if you don't know what power sagging is.
Earlier in the post (link), we tested the Lenkeng LKV373 kit and verified that the delay was insignificant - 0.067 seconds.
We recently examined the Lenkeng LKV383PRO over-IP extender kit, which upset us. Let's look into what the problem is.
What's the difference between a regular twisted-pair HDMI extender and an over-IP
1. Regular twisted-pair HDMI extender. The transmitter and receiver are connected to each other by a single piece of twisted pair (usually 130 to 330 feet). The twisted pair is used exclusively as some transport for specific signals. Video is transmitted in its original quality and without delay in this case.
2. Over-IP HDMI extender. Transmitter and receiver work on IP protocol, which means they can be connected to a local Ethernet network. The transmission range is limited to IP protocol, i.e., 330 feet. The range can be increased if a switch is connected between the transmitter and receiver in the middle. In this case, the video usually shows signs of slight compression and is transmitted with a small but visible delay.
An additional undeniable benefit of over-IP devices is the ability to connect additional receivers that connect to a LAN switch. They will display video from a single transmitter on that LAN without additional settings. Similar connection schemes can connect multiple TVs in a store to display promotional information.
When choosing an extender of the first type, everything is simple. You must decide on the maximum video resolution (FullHD or 4K) and video transmission range.
When choosing an extender of the second type, in addition to resolution and range, you need to pay attention to two more essential parameters: compression and delay.
HDMI over-IP extender image compression
Most low-cost HDMI over-IP extenders use video compression. An HDMI transmitter receives video at its input, encodes it with a specific codec (MPEG2, MPEG4, or other), and transmits it to the LAN network. The receiver receives this signal, decodes it, and outputs the video to the HDMI output. With this method of transmission, we may see a slight loss of image quality. At the same time, image deterioration can be observed only in some use cases. For example, when transmitting laptop desktop, showing documents. In this case, we can see a slight distortion of small details (letters, punctuation marks). When sending classic video content, image compression is difficult to see.
More expensive HDMI over-IP extenders use uncompressed transmission. Unfortunately, this device is still rare due to its high cost.
HDMI over-IP extenders video transmission delay
This parameter depends directly on the compression of the image. It takes time to encode and decode the image. Plus, more time for transmitting data packets in the IP network.
We experimented with Lenkeng LKV373 earlier and received an average delay of 0.067 seconds with a direct twisted pair connection without a switch. We considered this delay to be insignificant.
Recently we came across an older model of the same manufacturer - Lenkeng LKV383PRO. The main differences from the younger model are the transmitter's HDMI pass-through output and the IR signal reverse transmission.
When connecting it, we noticed a delay in video transmission, which was very noticeable. This upset us.
Having measured the delay, we got an average result of 0.5 seconds, which sometimes decreased to 0.2 seconds. Recall that the younger model managed in the same conditions for a relatively stable 0.067 seconds.
Instead of a conclusion
Who does NOT care? Let's say you have a TV receiver in one room and a TV in another. There are LAN outlets near the TV and the receiver. You can easily buy this set. It allows you to transmit video from one room to another. You can also remotely control the IR remote control of your receiver from the side of your TV. You won't notice any lag at all. Only a slight lag when scrolling through the menus.
Who cares? Suppose you are in a bar with a remote TV or...
In some cases, a successful result can only be reached with excellent and proper grounding if the probing signal is applied relative to the ground. An incorrectly selected generator grounding location will prevent the probing current from flowing in the search direction if the line to be traced is branched. The transmitter ground point should be changed so the signal is fed in the right direction.
The circuit impedance to which the signal is applied (cable-ground) depends on the ground condition (its type and humidity), the physical parameters of the traced line (size, insulation, etc.), and the characteristics of the grounding. Some generators can match the output impedance to the signal circuit parameters to increase the signal amplitude.
The grounding quality is essential for low frequencies. The better the grounding of the oscillator, the higher the signal amplitude. The ground resistance should be less than 1000 ohms. So a 5-gallon water canister will be helpful - water can always be poured into the grounding point and reduce the grounding resistance. A small metal plate is placed on the surface and watered if you encounter asphalt or concrete pavement. You do not need to use nearby metal structures (water pipes, fences) for grounding because they will emit a signal. You need to remember: if a parallel cable or pipe runs next to the cable to be traced, the reverse current will flow through them, and they will also emit an electromagnetic field therefore. It may take several attempts to experimentally find the best grounding point as a result.
The technique of routing pipelines and cable channels has its own features.
The generator is connected directly to them if they are made of conductive material. The pipeline must be disconnected from the ground at the point where the generator is connected. Otherwise, the signal will take a shortcut. It is worth using inspection pits for direct connection to a metal pipeline or cable channel in the middle of the route. If there are no inspection pits, the pipeline's location must be determined in advance by active or passive search. The connection quality of the generator (low contact transient resistance) to the metal cable channels is estimated by the change in signal level - the signal changes its tone when the load appears in most generators. When you trace cable channels and pipelines, you should always remember that the connection of their segments in some places can be made with non-conductive seals. It is advisable to connect such places galvanically so that you do not have to deal with each piece individually.
Tracing of non-metallic channels without internal conductive elements is done in two ways.
First, a metal CPS (Cable Pulling System) rod can be inserted into the channel, with the generator connected to both the rod and the ground.
Second, an active probe, a coil-loaded transmitter placed in a tiny capsule, can be inserted into the channel. The probe is attached to the CPS and pushed into the canal, and the active probe coil signal is detected by a receiver equipped with a coil sensor.
The first method is more convenient for tracing, and the second - is for finding specific locations (for example, to determine the location of a clog in the channel).
The signal can be fed to any two unterminated conductors of the cable or between one of the conductors and the building ground bus if you are using the sensor as an antenna.
Since the sensor-antenna "senses" the electric field, the signal is applied in such a way as to ensure its maximum (the circuit at the remote end must be open).
This must be remembered when the signal is applied to a pair of cores that has a defect in the form of a short circuit (reduced insulation) or is loaded (closed) at the other end since the electric field strength (its value is determined by the potential difference) will fall as you approach the point of short circuit.
I bought seven types of popular LED strips on Amazon. Three types of COB LED strips and four types of SMD (traditional) LED strips.
I'm not explicitly naming vendors because i think this will only mislead the reader. Most brands of LED products are now temporary brands. The brand is effortless to change if the brand does not mean anything to the seller. Today the product is sold under brand 1, and tomorrow the same product will be sold under brand 2.
I will test products of real A-brands (like IKEA or PHILIPS HUE) in the future, but for now, i'm interested in the current Amazon assortment.
The samples have different sector lengths, but i chose a sample length of about 1 foot.
Sample 1. COB strip.
Sample width: 25/64" Sample length: 11 13/16" Sector length: 1 31/32" Power supply voltage: 24VDC Declared power consumption: 4,57W/ft
Sample 2.
COB strip.
Sample width: 5/16" Sample length: 12 13/64" Sector length: 2 7/16" Power supply voltage: 24VDC Declared power consumption: 3.05W/ft
Sample 3. COB strip.
Sample width: 5/32" Sample length: 12 13/64" Sector length: 2 13/32" Power supply voltage: 24VDC Declared power consumption: 1.83W/ft
Sample 4. SMD strip on 2216 chips with a density of 149 chips/ft.
Sample width: 25/64" Sample length: 11 17/64" Sector length: 2 13/16" Power supply voltage: 24VDC Declared power consumption: 7.01W/ft
Sample 5. SMD strip on 2216 chips with a density of 81 chips/ft.
Sample width: 5/32" Sample length: 11 27/64" Sector length: 1 3/64" Power supply voltage: 24VDC Declared power consumption: 3.66W/ft
Sample 6. SMD strip on 2835 chips with a density of 73 chips/ft.
Sample width: 25/64" Sample length: 11 13/16" Sector length: 63/64" Power supply voltage: 24VDC Declared power consumption: 6.09W/ft
Sample 7. SMD strip on 2835 chips with a density of 18 chips/ft.
Sample width: 5/16" Sample length: 11 13/16" Sector length: 3 15/16" Power supply voltage: 24VDC Declared power consumption: 4.39W/ft
Test bench and measuring instruments
I created a unique test bench for experiments.
A sample LED strip hangs in the air with clips ("third hand" for soldering). The light from the LED strip is directed downward as in a real application (e.g., under a cabinet).
- The voltage is measured with a Greenlee 93-606 multimeter (accuracy for 24V DC = 1.2%).
- Current is measured with a Greenlee DM-65 multimeter (accuracy for DC < 0.6A = 1.2%).
- Temperature is measured with a Fluke TiS65 thermal imager (accuracy for temperatures 80-160 °F < 3 °F). The temperature is measured at the bottom (chips) and at the top (base of the strip). The device captures the maximum temperature in the central area of the field of view. This device property helps us find the hottest chips instead of their average temperature.
Measurement of current consumption. Comparison of real power consumption with the power consumption declared by the manufacturers.
Our samples are LED strips powered by DC voltage (not current!). Therefore, i monitored the 24V voltage during the entire test.
I measured each sample's current consumption and temperature after 30 minutes of operation. During this time, the strip is fully warmed up, and the operating parameters stabilize.
The samples have different lengths. I calculated the power consumption to the relative length of one foot to make a fair comparison. I also compared these values to the power consumption stated by the manufacturers of these strips.
I was unpleasantly surprised by samples 2 and 4. Terrible sample 5 with a difference of 23%. The overall conclusion is sad. The strips have a higher power consumption than the manufacturer claims. The total energy consumption of the lighting system will be more than the buyer wants.
Example. Sample 5 and a 23% difference. I use this strip to light the room around the perimeter of the ceiling. 60...
Let’s look inside a COB LED strip (and what is it anyway?)
1. Introduction. LEDs for the LED strip 2. Samples of COB strips 3. Removing the phosphor from the COB strip 4. Blue light 5. Damage to the individual LED chips and the effect on the operation of the strip 6. Comparing SMD and COB chips. What’s inside the SMD chip? 7. Chip density on LED strips 8. What i will do in the future
1. Introduction. LEDs for the LED strip
An LED (light-emitting diode) is a semiconductor that emits light by transmitting an electric current. LEDs are made from a silicon crystal (i.e., a chip). LEDs have both advantages and drawbacks. The most important ones are fragility (silicon is a very brittle material) and the inability to sustain temperatures over 200 to 250 °F.
The LED chips are protected from mechanical damage by a housing usually made from plastic. This housing also dissipates the heat from the chip to the surrounding objects (e.g., an additional heat sink).
The LED chip is placed inside such housing. There are miniature copper conductors inside the housing for the electrical connection of the chip. On the outside of the housing, there are copper conductors that a used to connect the housing to the surface (circuit board, tape, wires, etc.).
Enclosures can be different. SMD (Surface Mounted Device) housing technology is traditionally used for the mass production of LED strips.
Different shapes of housings The SMD housings are soldered to a flat long base with copper conductors to make a strip.
Notice the yellow-orange spots. This is a phosphor, a substance that absorbs and emits (re-emits) light creating a glow of the desired color or combination of colors.
What is it used for? White light is created by blending several colors from dark red to violet. A simple case is RGB. These are three colors (red, green, and blue). But this kind of white light isn’t a good solution for lamps, as the lighted objects look faded and gray. To get high-quality white light, you need to mix many individual shades of color. The more color shades are mixed, the greater the quality of the resulting white light.
The LED chips can only shine in one color. Red light is emitted by one LED. To emit dark red, a second LED is needed. Light-green needs the third LED, dark green — one more LED, and more, and more of them… You need many individual LEDs to create a quality white color.
At the same time, the efficiency of conversion of an electric current into light in LEDs is low for the red color and high for blue one. This means that the red LED will consume significantly more energy than the blue LED with the same brightness.
It would require a massive structure with many LEDs and additional electrical circuitry. It would be complicated and expensive.
But scientists have come up with a phosphor. This is a mixture of different chemicals that absorbs light of only one color and re-emits light in many different colors. This allows only one LED chip (with one color) to be used to create white light from dozens of shades of different colors. What color to choose for a single LED? Since the efficiency of a blue LED is much higher than a red LED, it is possible to use a blue LED as the base-emitter, getting a lot of light from a small amount of electricity.
In SMD technology, the phosphor is applied on top of the housing above the blue LED chip.
COB (chip-on-board) technology is the most modern. It means that the LED chip does not have a separate plastic housing. The chip is soldered to the built-in copper conductors on the strip base directly. The phosphor is applied to the strip from above in a continuous layer. Much more phosphor is required in production, but considering the advantages of the technology, it is not important.
The base of the COB phosphor is silicone. It is a soft material to keep the tape flexible. Also,...
I measured the LED chips' temperature and the strip base hanging in the air in the last experiment. Now i simulated mounting the strip under the cabinet in a groove ½" deep.
- At the bottom of the groove. Direct contact between the LED strip and the chipboard. Without an optical diffuser.
- At the bottom of the groove. Direct contact between the LED strip and the chipboard. Additionally, i install a diffuser. The diffuser/shield closes the ambient air access and blocks the heat dissipation from the LED chips through the air. I do the temperature measurement immediately after removing the diffuser to access the measuring device.
Test bench and measuring instruments
I created a special test bench.
without a diffuser with a diffuser I measured the temperature of each sample after 30 minutes of operation. During this time, the LED strip is fully warmed up and its temperature stabilizes. Generation and dissipation of heat from the LED chip without diffuser.Generation and dissipation of heat from the LED chip with diffuser.
I make sure that the 24V power supply voltage remains constant and i measure the temperature of the LED strip chips in a room with an air temperature of 73 °F. I use a professional Fluke TiS65 thermal imager (accuracy for temperatures 80-160 °F < 3 °F).
Fluke TiS65
This device records the temperature of the hottest chips in the central part of the field of view.
Example of automatic search and display of the hottest point in the central part of the field of view.
I also record the heating of the chipboard on the back side. I evaluate the effects of the chipboard's thermal conductivity and the danger of heat to objects inside the cabinet.
Results of chip temperature measurements of LED strips on chipboard
THERMAL IMAGES. LED CHIPS ON CHIPBOARD WITHOUT THE DIFFUSER
THERMAL IMAGES. LED CHIPS ON CHIPBOARD WITH DIFFUSER
THERMAL IMAGES. DIFFUSER OUTSIDE
THERMAL IMAGES. CHIPBOARD BACKSIDE WITH LED STRIP WITHOUT A DIFFUSER
THERMAL IMAGES. CHIPBOARD BACKSIDE WITH LED STRIP WITH DIFFUSER
I want to explore the effects of the heat sink commonly used with LED strips this time around. A simple 15" x 1" x 1/25" + 1/2" x 1/25" L-shaped aluminum profile was at hand. I glued the LED strips alternately to this profile.
Test bench and measuring instruments
I measure the temperature in a room with an air temperature of 73 deg F using a professional Fluke TiS65 thermal imager. I also use our past test bench, a simulated cabinet. (Learn more about previous results)
I added mounts to this bench to hang the profile and LED strips in the air.
Types of our measurements
1. LED strip on the aluminum profile in the air. I measure the temperature of the LED chips and the heating of the aluminum profile backside (heat transfer from the base of the LED strip to the profile).
2. LED strip on the aluminum profile in the air. I measure the temperature of the LED chips and the heating of the aluminum profile backside (heat transfer from the base of the LED strip to the profile).
3. LED strip, covered with a diffuser, on an aluminum strip in a chipboard groove. I measure the temperature of the LED chips and the chipboard heating on the backside.
This type of measurement completely simulates conventional LED fixtures sold in stores. The heat from the LED chips is removed mainly by the strip base and the heat sink. Air convection is negligible. The plastic diffuser creates a fixed air layer near the LED chips.
Results of chip temperature measurements. LED strips on aluminum profile in chipboard
THERMAL IMAGES. LED CHIPS ON AL PROFILE IN AIR
THERMAL IMAGES. AL PROFILE BACKSIDE IN AIR
THERMAL IMAGES. LED CHIPS ON AL PROFILE IN CHIPBOARD WITHOUT DIFFUSER
THERMAL IMAGES. CHIPBOARD BACKSIDE WITH LED STRIP ON AL PROFILE WITHOUT DIFFUSER
THERMAL IMAGES. LED CHIPS ON AL PROFILE IN CHIPBOARD WITH DIFFUSER
THERMAL IMAGES. CHIPBOARD BACKSIDE WITH LED STRIP ON AL PROFILE WITH DIFFUSER
In past experiments, i noticed the LED chips temperature on the chipboard compared to the LED chips temperature in air. This temperature was higher! This seemed strange to us, because the thermal conductivity of air is much lower than the thermal conductivity of chipboard. The heat should go into the chipboard better than into the air.
Where did i go wrong? How does the heat from the LED strip dissipate the air?
Data from past experiments: 1. LED strip chip temperature, suspended in the air. 2. LED strip chip temperature, glued to the aluminum profile and suspended in the air. 3. LED strip chip temperature on chipboard. 4. LED strip chip temperature, glued to the aluminum profile on the chipboard.
In many cases, the LED chip temperature has increased on the chipboard, not decreased.
I think the clue is in the movement of air near the LEDs (heat sources), not in the thermal conductivity of the air. The effect of convection - warm air moves up, and cold air moves down. The air is heated by the LED chip and moves upwards, taking the heat away. In its place comes the cold air, which heats up and goes up. So the heat from the chips goes into the permanently cold air, effectively taking that heat away.
Measurement description
To confirm this theory, i will modify the test bench from the previous parts of the experiment (learn more) .
I will add a thick layer of extruded polystyrene (XPS). I will create an obstacle for the rise of warm air from the LEDs in the form of an extended flat surface. I use XPS because this excellent material has a very low thermal conductivity. Therefore, it will not be a heat sink for the LED strip base. I investigate only the air movement.
Test bench and measuring instruments
The measuring instruments and the other things were the same as in the last experiment (learn more).
Measurement results of LED strip chip temperatures on XPS
The Lenkeng LKV372AE extender is considered basic in Lenkeng's lineup. It transmits video with a maximum resolution of 1080p at 60 Hz for a distance of up to 230 feet over a CAT6 cable. It should be noted that the cable category is based on the requirement for a 23 AWG wire cross-section. Theoretically, you can use CAT5e cable (24 AWG) and the range should be at least 130 feet. Going forward, during the tests i got more encouraging results for the range on CAT5e cable.
External view
The kit comes in a gray box without any advertising pictures. This usually suggests more professional applications, where "wrapping doesn't matter".
If you open the box, you can immediately see the transmitter, the receiver, and the instructions. Additional accessories (power supplies, IR transmitter, and IR receiver) are located under the soft padding.
The receiver and transmitter have a very compact design. What catches your eye are the lugs on the housing for easy mounting to surfaces. They will come in handy if you need to screw it to a wall or under a table. The transmitter and receiver housings are made entirely of high-quality metal. Except for the plastic overlay with HDMI Extender labeling, which displays the maximum range (70 meters is 230 feet) for information and to identify the Transmitter or Receiver. This plate is covered with a protective film that can be removed after installation.
There are connectors for HDMI, power, and IR transmitter and emitter connection on the front side of the transmitter and receiver. There are also the Reset button and the LED indicator that helps to determine if there is power and if there is contact between the devices. I would like to note a good fit of the inner board with connectors to the housing. All parts fit with minimal gaps and nothing inside is loose if you shake it.
In the package, you can find an IR emitter and an IR emitter for sending the IR signal back. This additional feature is very useful for controlling an IR remote control, e.g. a TV set-top box from the TV side. The Transmitter and Emitter come with double-sided adhesive tape for attaching to surfaces. It is very odd that it is supplied separately and not glued immediately
Right away i want to note the thickness of the metal from which the housing is made. It is thick enough. Perhaps this is because the smaller the housing, the better heat dissipation is needed. Anyway, i can see that the manufacturer did not try to save money here.
The board is inserted in special slots that secure it. And the edges of the board are insulated with special tape. In our opinion, the soldering is of high quality. The only disappointing thing is a little bit crooked gluing the cooling radiator to the chip. But it shouldn't affect the performance.
Performance testing
I prepared a small test bench which consisted of a laptop, a monitor, and a set of HDMI cables, CAT6 and CAT5e of several lengths. I would like to point out that for testing i used 6-ft HDMI cables, which is the standard for cables that come with many devices (monitors, TVs, set-top boxes). Initially, i tested the operation in standard mode - video transmission with 1080p 60Hz resolution using a CAT6 cable 230 feet long. I had no complaints at all. The video was transmitted on the laptop monitor and the external monitor through the transmitter and receiver set without distortion and visible delays.
During the next test, i replaced the CAT6 cable with a CAT5e, which has a smaller cross-section (CAT6 is AWG23, CAT5e is AWG24). Although the difference in the diameter of these cables is 20%, the vendor claimed that the kit should transmit video to a distance of up to 130 feet when using CAT5e cable. Maybe he decided to play it safe. I started our tests with 190 feet.
The test result surprised us because everything worked flawlessly. I can assume that it's all about the claimed performance characteristics:
In addition to the basic 1080p60Hz video specification, the manufacturer has said that 4:4:4...
I had another twisted-pair HDMI extender up to 230 feet for testing - Lenkeng LKV375N.
This is an inexpensive extender that works on HDBaseT technology. This means it is interchangeable with equipment from other manufacturers that work on the same chips
Main Features
The Lenkeng LKV375N is a ready-to-use kit for transmitting HDMI signals with up to 4K@30Hz resolution over a twisted pair at a distance of up to 230 feet. Additional features include additional IR signal transmission in both directions.
External view
The set is packaged in a gray package. Such packaging is found in almost all professional devices. This emphasizes that "wrapping doesn’t matter, but the content does".
If you open the box, you will immediately see the transmitter, receiver, and instructions. The rest of the accessories (power supply unit, IR transmitter, and IR receiver) are located under the black blister.
The transmitter and receiver are of average size for such devices and are made of quality metal.
There are a lot of vents in the housing of the devices, which seem to hint at increased heat dissipation. I will test this during the testing. There are also threaded holes on the sides of the housing. They may be used for additional mounting ears which i did not find in the kit. Moreover, there is not a single word about it in the manual. Still, i consider it to be a useful feature for fastening the box to various surfaces.
The kit also includes an IR transmitter and an IR receiver for remote control of either a display device or a video source. Remember that the kit has two-way transmission of the IR signal. Of the disadvantages, note that the double-sided adhesive tape is supplied separately and not already glued to its seats. But this is not a significant drawback.
After removing the cover, i found a rather large radiator on the main chip. Now it is clear why there are so many holes in the housing – they provide for better heat dissipation. You can also note the slightly skewed adhesion of the radiator to the chip. This does not affect its capabilities but should be noted as a fact.
Otherwise, there is no question about the quality of soldering - all is neat and high quality.
Performance testing
When connecting i use our test cable twisted pair CAT6 230 feet. Initially, i feed the image at 1080p at 60Hz. The set is up and running. The video was transmitted with no visible delay and no degradation in quality.
As the next step, i decided to test the claimed 4K video transmission at 30 Hz at a distance of 115 feet, which the manufacturer claims in the manual. Initially, i purposely set the frequency to 60 Hz. As expected, the video did not transfer. When i changed the frequency to 30 Hz it worked. There is not enough bandwidth to transmit more frames.
Conclusion
At first glance, the tested set showed the usual results, as the declared characteristics were shown during the test. But mind one significant thing - the price. The transmitter and receiver kit is cheaper than many other manufacturers' HDBaseT transmitters or receivers sold separately. If it's the transmitter and receiver kit you need, it would be a good choice in terms of price.
When purchasing a twisted-pair HDMI extender, it is useful to check if it has any additional functions. One of them is the ability to transmit the IR signal. In this article, i will look at the types of IR transmission, and explain what they are needed for and how they are implemented.
Let's look at an example of two extenders: Lenkeng LKV372AE-4.0 and Lenkeng LKV676E (twisted-pair HDMI extenders up to 230 feet)
IR signal pass-back
The Lenkeng LKV372AE-4.0 is a simple twisted-pair HDMI extender that has the additional function of sending the IR signal back. This means that i send an HDMI signal from the transmitter to the receiver (i.e. from the TV tuner to the TV) and i can send an IR signal back (i.e. from the TV to the tuner).
In other words, if your TV tuner is in the living room and you want to watch TV in the bedroom, you need to lay a twisted pair from the tuner to the TV in the bedroom. Then connect an HDMI transmitter to the tuner and a receiver to the TV, as in the diagram above.
Now i need to ensure a comfortable switching of the TV tuner channels. To do this, i additionally connect the IR blaster (included with the extension cord) to the HDMI transmitter and attach it to the TV tuner with the included double-sided adhesive tape. Connect the IR receiver (also included in the package) to the HDMI receiver, and attach it with double-sided tape in a convenient place where i will direct the IR remote control. Usually, this is the frame of your TV set.
Now the video signal will be transmitted over twisted pair from the tuner to the TV, and the IR signal will go back from the TV to the tuner.
And this is the principle of IR signal pass-back.
Bi-directional IR signal transmission
Bi-directional IR transmission can be explained in the example of the Lenkeng LKV676E twisted-pair HDMI extender.
On the body of the transmitter and receiver, you can see two ports to connect the IR: In and Out. Depending on the task i have to use the right input.
If i have already solved the first problem (the IR signal pass-back), then why should i transmit the IR signal from a transmitter to a receiver?
This is more used in commercial applications, e.g. the TV is in the lounge in the cafe, and the TV set is somewhere at the bartender's workplace. The bartender wants to turn off the TV, or switch the input source without going close to the TV set. So with the feature, i kind of extending the IR remote control signal of the TV over a long distance.
In this way, i get a more versatile transmission of the IR signal in both directions. This does not mean that you have to buy a device with a bi-directional IR signal function. Just think if this scenario is required or not.
I noticed that my LED strip samples have different base thicknesses. Most samples are thin and bend easily; some are thick and hold their shape well after bending. I found only one metal in the strip base. The copper conductors transmit the power along the tape to all the LEDs. I thought that the inner conductors' different thicknesses meant different electrical characteristics. Aha! There's a lot to study here!
Next, I'm talking about regular strips no more than 1/2" wide with constant voltage.
Why are the conductors in the strip important? Many types of LED strips are high power to generate a lot of light (shine brightly). The more power, the more current. The conductors must be thicker and wider (cross-sectional area) to allow more current flow. Power losses will appear in the conductor, and that conductor will heat up if that area is not large enough. So less electricity will reach the far-end LEDs, and they will shine less. If the LEDs emit light with different intensities depending on their location - it is a bad strip.
So. The current through LED strip conductors depends on the power of that strip and can be up to 0.5 Amps for each foot of strip (8 Amps (!!) for a 16-foot (5 meters) strip).
The resistance of a conductor is measured with a milli-(micro)ohmmeter usually. I don't have such a device, but I took measurements using this device's method. I mean the 4-wire method (Kelvin method). I measured the current through the conductor to be measured (as well as through the ammeter wires), also the voltage on that conductor at the beginning of the strip (not at the power supply output!!!! This is important!).
The resistance of the wires from the power supply and the ammeter (on the contacts of the LED strip) is excluded in this way of measurement.
The resistance of the voltmeter wires is unimportant because the voltmeter has a considerable internal resistance (usually mega ohms).
- The voltage is measured with a Greenlee DM-65 multimeter (accuracy for 0.5V DC = 0.9%).
- Current is measured with a Greenlee 93-606 multimeter (accuracy for DC < 10A ~ 2.5%).
- Power supply - RIDEN RD6024 precision power supply (I bought this power supply on Aliexpress and looked through many positive reviews on the Internet).
Measured data
Next, a simple calculation.
I multiplied the operating current of the LED strip and the internal conductor resistance. That's how I calculated the voltage reduction for a 16-foot strip. The LED chip section will not get 24 volts through 16 feet, but 24 volts minus the voltage reduction on the internal conductors.
20% or more is terrible, I think. Guys, and that's for LED tape that is only 16 feet long!
And here's the calculation for 32 feet. Just double the length.
47% !!! Half of the electricity is lost!
Conclusions
- Professional installers always connect LED strips no longer than 16 feet (5 meters) to the power supply. Otherwise, the voltage drop on the internal conductor is too significant. A large voltage drop is a large drop in light output on the far segments. LED strips more extended than 16 feet are connected in parallel pieces to the power source/s through thick copper wires to each piece.
- Cheap, low-quality LED strips cannot even be connected in 16-foot sections. Such strips have thin internal conductors with a significant reduction in power supply. Bad manufacturers skimp on the thickness of the inner conductors of their strips and create problems for customers.
- The 24V power supply voltage is much better for high-power bright LED strips. More voltage, less current. Less current, less voltage drop on a long strip. The manufacturer must use thick internal conductors for high-power LED strips of 12V (and even more so 5V!). Such strips will be expensive and hard to install. For example. Imaginary LED strips have the same power and internal conductors as my samples but with a voltage...
Wire tracing can be performed using two modes: passive and active.
The passive mode can be used to trace electrical wiring that has a current going through it. The electromagnetic field of the wire can be detected with a receiver that is equipped with either an inductive sensor (if an electric current is flowing through the wire) or a capacitive sensor (if there is no electric current present in the wire). The main disadvantage of this mode is the possibility of getting strong interference from other power lines, electrical appliances, and/or metal studs.
Therefore, the passive mode is very rarely used for tracing and identifying electrical wires when using professional devices.
During active tracing mode, a device generates a signal that is sent through the wire at a frequency different from the primary power line frequency (50/60 Hz). In this case, the signal can be sent through either a disconnected line or a live one.
Remember, conductors in the wiring cables are run in parallel. Let's assume that one sends signals through a pair of wire conductors that are opposite the line phase. In this case, the generated electromagnetic fields will be mutually compensated. Resulting electromagnetic field will be weak and hardly detectable.
For example, let's say a wire runs inside a metal cable duct. If you send a signal between one of the cable cores and this duct, mutual compensation of the signals will also be detected. It is easier to trace a wire in the points where cable cores are separated (e.g., in the switchboard, socket, or junction box). It is enough to just separate a wire pair by 1-3 cm to perform tracing. Then a signal can be sent through the wire pair as the next step.
The easiest way to trace a disconnected line is to send a generated high-frequency signal to the wire pair. Then, a capacitive sensor should be used in order to detect the generated electromagnetic field. In the case of a three-wire power line, it is recommended to use the phase-neutral wire pair. Do not use the phase-ground and neutral-ground pairs in order to avoid the risk of unwanted ground loops.
It is important to remember that the neutral wire should not be conductively-coupled with a natural grounding electrode (for example, a water supply pipe). If this is unavoidable, the signal generator can be connected to any large metal object instead of neutral (for example, the metal frame of furniture). However, the trace distance will be significantly reduced in this case.
It is often necessary to identify cable wires while performing tracing. In this case, wires that are not receiving a signal should be grounded. Grounding must be provided at the signal generator connection point. This will significantly reduce the amplitude of the signal induced on the wires and make identification easier even if the cable is long.
There are three ways to send a signal to live wiring in the active tracing mode.
THE FIRST WAY
is to use a signal generator that provides resistive load with alterating resistance at a constant frequency. When you connect such a signal generator to the mains socket, the wires will start emitting a specific signal. This signal can be detected by a receiver with an inductive sensor. Moreover, the alterating resistance of the signal generator has no affect on the operation of the equipment that's connected in parallel, nor the alterating resistance of any other device.
In this case, the wiring can only be traced from a specific socket to the switch or breaker that's located inside the switchboard. However, you can find a switchboard and identify the relevant circuit breaker inside it without even performing line tracing.
The signal from such a signal generator goes from the load towards the power source. It can successfully overcome transformers. Thus, the signal amplitude varies in accordance with transformation ratio. But this signal is not passed along to circuits that are connected in parallel (e.g. other mains sockets). This hapens due to the fact...
Only a few buyers of twisted pair network cable HDMI extenders pay attention to the additional features of some models. One of these features is the HDMI Loop Out from the transmitter.
Let's take a look at what this feature is and its intended use, and then decide whether it is adds the necessary value for the money.
What does “HDMI Loop Out” mean?
A standard twisted pair network cable HDMI extender kit includes a transmitter and a receiver. The transmitter has an HDMI input and a RJ45 port. The HDMI input can be used, for example, to connect a TV tuner. The RJ45 port is provided for the twisted pair network cable connection. The receiver has an HDMI output and an RJ45 port. The HDMI output can be used, for example, to connect a TV. The reciever's RJ45 port is also used for the twisted pair network cable connection, just like the transmitter.
The main purpose of such a kit is to provide an HDMI interface extention of up to 230 feet (the image above shows the Lenkeng LKV372AE-4.0 device).
Another example for its use is a situation when you want to watch the same video feed on two TVs simultaneously. In this case, one TV would be next to the TV tuner, and the other is at some distance. In this case, i need to split the HDMI signal. This is usually done with the help of a splitter device. But this would mean having to buy an additional device, and then having another active device in your setup. A better solution would be to use a twisted-pair HDMI extender kit, where the transmitter is equipped with the HDMI Loop-out.
For this case, i can to assemble the following wiring diagram. The Lenkeng LKV372Pro device is shown in the example.
Conclusion
All in all, i can see that implementating the HDMI Loop Out feature is relatively easy. However, manufacturers sometimes ask extra money for this feature. If you really need to connect TV locally near the source, as you can see in diagram 2, then this solution is the real find. If you plan to use the extension cable as shown in diagram 1, you definitely should avoid overpaying for the HDMI Loop Out feature. However, this is only relevant provided that you have the choose between “with this feature” and “without this feature”.
I have measured the LED strip temperatures in different strip placements.
1. LED STRIP SUSPENDED IN THE AIR.
Air without motion (limited volume) has low thermal conductivity. But when air moves, the situation changes significantly. Air can pick up and take away a lot of heat, and this effect is used everywhere. For example, in computers, a fan is constantly blowing cold air through the processor's heat sink. This cold air takes excess heat from the processor and gets hot. And then the hot air is blown outside.
The air moves near a hot object even without a fan. It is convection - warm air rises, and cold air falls. The LED chips are cooled by air convection in this placement. The air passing near the chips heats up and rises, taking heat from the chips.
For this LED strip cooling variant: (pros) easiest. We don't need any additional materials. (cons) Significant heating. LED strip bends from its gravity and does not protect against mechanical influences (easy to damage), dust, or water droplets.
2. STRIP IN THE GROOVE IN THE CHIPBOARD.
The LED chips are cooled by air convection and heat transfer to the chipboard.
For this LED strip cooling variant: (pros) simple - the tape is glued to the furniture element (for example, under the cabinet). (cons) Significant heating. LED chips are not protected from mechanical influences, dust, and water droplets.
3. STRIP IN THE GROOVE IN THE CHIPBOARD AND COVERED WITH A DIFFUSER.
The LED chips are cooled primarily by heat transfer from the chips to the chipboard. The air convection is minimal because no cold air enters the LED chips.
For this LED strip cooling variant: (pros) simple - the strip is glued to the furniture element (for example, under the cabinet), and the diffuser is inserted into a slot in the chipboard. LED chips are protected from mechanical influences, dust, and water drops. (cons) Extremely high heat.
Aluminum has a high thermal conductivity. This material quickly picks up heat from the LED chips (through the metal base of the tape with high thermal conductivity) and distributes this heat evenly over its volume. This design greatly increases the air's contact area and convection (see point 1). More convection means more cooling.
For this LED strip cooling variant: (pros) Efficient - LED chips are very well-cooled. The aluminum profile is an excellent housing, protecting the LED chips from mechanical damage. Also, the profile can be any shape and beautiful color. (cons) LED chips are not protected against mechanical damage, dust, and water drops.
6. THE STRIP ON THE ALUMINUM PROFILE IN A GROOVE IN THE CHIPBOARD WITH A DIFFUSER.
I simulate the light fixture under the chipboard cabinet entirely. The air convection is minimal because the diffuser blocks the cold air to the hot LED chips.
(pros) LED chips are well protected against mechanical damage, dust, and water droplets. (cons) None
The task of this test model is to estimate the strip heating without heat dissipation in the chipboard and with minimal air convection. This data will be helpful for comparison with other data.
This post contains a brief introduction to cable location principles. What does a typical locator consist of? Active/passive location methods. Cable connection methods.
Determining the route of an underground cable or conduit is a common challenge. This challenge can be overcome with the help of special measuring devices. Although they have a similar principles of operation, they can have different names, such as cable locator, cable avoidance tool (CAT), underground wire locator, or cable tracer. Using these devices, it is possible to successfully determine the route of all sorts of cables (even fiber optical cables, given that they are equipped with a metal cordage or jacket). Moreover, these devices can sometimes detect the location of cable faults, such as cable damage or a short circuit.
Locators that were used to search for metal objects underground were first introduced 40 years ago. Initially, they were only used to detect water, gas, or sewer pipes. Today this issue has become significantly more complicated. In addition to metal pipes, an enormous amount of power and telecommunications cables have been laid underground. Over the years, cable locators have become more accurate and now come with new features. However, they still use the same fundamental technology as the very first models. This technology is based on electromagnetic field detection.
How do the aforementioned devices work? The cable locator consists of two parts: a signal generator (transmitter) and a receiver (detector). The former sends a signal to the cable line, while the latter detects it. It can be said that the receiver serves as the "heart" of the cable locator. Firstly, its characteristics and features determine the aggregate capabilities of the generator-receiver pair. Secondly, in some use cases, a generator may not even be required.
The cable locator receiver needs at least one sensor to "pick up" the electromagnetic field. This can come in the form of a whip antenna (capacitive sensor) or a coil (inductive sensor). Both have specific advantages and disadvantages. Therefore, some devices have one or even several (two or even three) replaceable sensors. The signal that they receive is amplified and processed. The resulting processed signal is presented to the operator.
The signal can come from either a voltage or variable frequency current generator (200 Hz - 130 kHz). Some generators have a single fixed frequency. Others have multiple range of operating frequencies (up to 4) that can be chosen based on the use case. Some generators can generate a signal of several frequencies at the same time. And in some cases two frequencies may alternate.
A detection method is considered active if both receiver and generator are utilized. However, a sensor can also detect electromagnetic fields that are generated by other signal sources. This allows the device to detect and trace the routes of loaded power lines (50 Hz and higher harmonics of up to 3 kHz), cathodic protected pipelines (100 Hz), telephone cables via alarm signals (2-18 kHz), wired broadcasting networks (300 Hz - 130 kHz), as well as any conductive objects that have external radio transmitters which can induce a signal in long wave range (140 kHz - 300 kHz), and others. In such cases, the tracing can be performed in passive mode. In other words, it means that the use of a generator is not necessary.
In active mode, the signal can be sent to the cable via several different methods. The generator's signal can be sent directly to the cable (direct connection), via an inductive antenna (remote antenna) or through an inductive coupler (signal clamp).
The direct connection method is self-explanatory. The transmitter must be physically connected to the cable that's being traced. However, if this is impossible, one of the other two methods can be implemented.
An inductive antenna is a coil that receives a signal from the generator. The antenna is placed directly above the cable and induces a signal in it. Of...
There aren't many consumers who pay much attention to design when choosing an HDMI extender over a twisted pair network cable. But it can be quite important in some cases. What if you choose a compact type of extender?
If you remember, an extension kit includes a transmitter and a receiver.
If you conduct a Google search, you will see a wide variety of HDMI extenders available on the market. All the extenders have HDMI inputs and outputs, as well as RJ45 twisted pair network cable ports. Some models have additional ports such as an IR, RS232, and others, which provide the devices with advanced features.
But you can also find devices that are smaller in size than others. The transmitters and receivers of such devices normally include built-in HDMI plugs.
Such an extender can seem like a good choice at first glance. A compact size, lower price, and no need for additional HDMI cables. So many advantages – you might be compelled to order one right now! However, in practice, this type of HDMI extender is not suitable for every use case.
Let's take a look at an example. I have put the Lenkeng LKV372S extender to the test. It has a compact size and built-in HDMI plugs. It is powered by a USB port, with a USB to micro-USB cable included. For example, the transmitter can be powered using an available USB port on a laptop. And the receiver, in turn, can be powered using special USB+ port on a TV.
More often than not a laptop's HDMI and USB ports can be located very close to one other. In such cases, the transmitter unit will block the adjacent ports. This limits the usability of such a kit to a great extent.
The same situation can also happen with the TV and receiver unit.
Another important factor to consider is the flexibility of the twisted pair network cable. Usually, it is less flexible than a short HDMI cable. With the implementation of compact HDMI extender, you will not be able to freely move the laptop around on the surface of the table. Therefore, such a solution would be more suitable for connecting to a desktop computer.
LED luminaires use different connectors to connect the power supply and the light emitter or to extend the wires (for example). Manufacturers and retailers describe the current that can safely pass through the connectors for long periods.
I want to test the connectors for LED lights and strips with the maximum current. I want to measure the heating of the connectors and answer the question - "can the connectors be used at the stated/specified current for a long time." I also want to determine the critical current level at which it is dangerous to use the connector.
I want to determine the hazard by connector temperature (fire hazard) and smoke generation (poisoning hazard).
Samples
L814-L816
The first connector has different names. You can suggest variants in the comments or write me. I call this connector L814-L816 (also known as L813-815).
L814 Plug (“male”) / L816 Socket (“female”) Max current: 3А Wire: 22 and 24 AWG
DC21-55
The second connector is known to me as DC 21-55 plug- socket (male – female).
Plug. Outer diameter: 5.5 mm / Inner diameter: 2.1 mm Contact size: 9.5 mm
Socket. Outer diameter: 5.5 mm / Inner diameter: 2.5 mm Contact size: 10 mm
Max. current: 5A
Wire: 18, 20, 22, 24 AWG
HIPPO LED STRIP CONNECTOR (WITHOUT SOLDERING)
The third connector connects directly to the LED strip without soldering. Maximum current: 5A
Experimental bench
I hang the connectors and wires in the air with clamps. I short-circuit the wire on one side, and connect the other side to a powerful power supply.
I use a piece of LED strip with a thick jumper soldered on to test the Hippo connector.
I will adjust the voltage to within 0.01 volts to get the right current level - good old Ohm's Law (I = U/R).
So.
I need a power supply. And it's the RIDEN RD6024 high precision laboratory power supply. The integrated ammeter of this power supply will measure the current level. In my past experiments, I have verified that this is an accurate ammeter.
I will also use the Fluke TiS65 thermal imager (accuracy for temperature 80-1000 F = 2%) to measure the outside temperature of connectors and wires.
I will apply the required current to each sample for 30 minutes, measuring a stable temperature. I will also measure two identical samples to study the repeatability of the results.
Measurements
L814-L816 CONNECTOR
The connectors only heated up to 92 F at a 3A current. I measured another pair of the same connectors and got the same result. These connectors can be used at currents up to 3 Amps.
The same connectors heated up to 112 F at +50% of the maximum stated current = 4.5 Amps. Good!
At ten amps, the connectors heated up to 251 F. They didn't collapse, but they are very hot.
Finally, at 15 amps, the connectors quickly (1 minute) heated to 410 F and melted, producing stinky smoke.
The connectors are heated to 93 F at 5 Amps. These connectors can be used at currents up to 5 Amps.
These same connectors only heated to 136 F at +100% of the maximum stated current = 10 Amps. That is an excellent reserve.
But at 15 amps, the connectors quickly heated to 277 F and melted, releasing smoke.
HIPPO LED STRIP CONNECTOR (WITHOUT SOLDERING)
The connector only heated to 114 F at a 5 Amp current. These connectors can be used at currents up to 5 Amps.
The connectors heated to 199 F at a current of +50% of the maximum stated current = 7.5 Amps.
At a current of 10 amps, the connectors heated up to 297 F. The case remains intact.
At a current of 20 Amps, the temperature increased to 470 F. The connector began to melt and emit smoke.
It's interesting. The heating centers are marked not in the "teeth" (places where the LED strip is pierced) of the connector but in the areas where the connector contacts the wires.
How does a generator's signal frequency affect the range of the cable location signal? What cable identification frequency is more efficiently? Why can cable identification at low frequency be more reliable? And when is passive location used?
Cable tracing devices consist of a generator and a receiver. Some generator types have the option to choose a frequency (usually in the range of 200 Hz - 130 kHz). Moreover, choosing the correct frequency is incredibly important. The value of the frequency affects the working distance of the cable location signal. This is the distance at which the receiver "picks up" the signal from the generator.
The impedance of a long cable is predominantly capacitive. As the frequency increases, the signal leakage from the traced cable into the ground also increases. The power of the current also decreases faster along the length of the cable. Consequently, the distance where the cable location signal can be detected also decreases.
By the way, this explains why the cable (or pipeline) diameter affects the signal detection distance. The larger the surface area of the cable shielding or pipeline, the greater the increase of current leakage to the ground that one can observe. This leads to a decrease in the signal strength over the length of the power line. Therefore, when a signal is sent over a power line with a smaller diameter, it can be detected at a greater distance from the transmitter. However, it is only true up to a certain point. To close the circuit (and increase the strength of the current), it is necessary to ground the far end of the routed power line.
Circuit impedance also depends on the soil's conductivity. The soil structure (loose or dense) and moisture content affects two things: the return current conditions and its leakage into parallel lines. The former is simple and easy to understand. The impedance of moist and dense soil is lower than that of dry and loose soil. If the soil is moist and dense, the strength of the current in the circuit will be higher. However, leakage will increase as well. Generally speaking, a thin cable that's laid in the desert can be detected at a much greater distance from transmitter than a thick cable laid that's in a swamp.
Let's imagine that a cable and a metal pipeline are laid side by side in soil that has low conductivity. If you route a cable in such soil, return current will flow through the pipeline. The impedance of the circuit will decrease and the current will increase. But now the pipeline with the return current flow will also emit a signal. In such case, tracing the cable will most likely not become easier.
The frequency of the signal also affects the difficulty of routed line tracing when there are several power lines running in parallel. The higher the frequency, the greater the signal that's induced in the parallel lines. This makes it more difficult to identify the necessary cable. Let's assume that a parallel line is routed at shallower depth than the one being traced. Thus, the signal detected from this parallel line can be stronger than the one coming from the line that's connected to the generator.
So, a reduction in frequency leads to increase in detection range of the cable location signal. It also makes it easier identify a traced line among several parallel lines.
Cable tracing at high frequency
Further, let's consider the operation of a cable locator at a high signal frequency. There are four main reasons to use a high-frequency signal during cable tracing.
Firstly, a high-frequency signal is required for the proper operation of an inductive antenna and an inductive transmitter. These devices are used to generate a signal to the line being traced without a direct connection. The induction method cannot be used to transfer a low-frequency signal at the necessary distance.
Secondly, the higher the frequency, the higher the current induced in the line being traced. This is true for both cables that have a small diameter and length, as...
Although plenty of people buy a twisted pair network cable HDMI extender kit, few think about how to mount it properly.
In one of our articles (link to compact extenders) i talked about the hidden pitfalls of compact HDMI extenders. Now i would like to talk in detail about the "regular" kits. For the most part, they have a standard form: a metal case with a minimum set of inputs and outputs (HDMI, RJ45, power).
Of the new users of such kits, few understand the importance of its external appearance and configuration in terms of how it will be further installed in the room. When choosing a kit, it is important to consider the following question. How are you planning to position this device? Are you planning to hide this device on a table behind an NVR, TV, monitor, etc.? Or will the transmitter and receiver be placed in plain sight, e.g. on a wall, under a tabletop, or on a surface in some other way? That is why it is important to pay attention to its form factor and the kit itself.
Most extenders look like a regular box:
There are extenders that have special mounting brackets built into the case itself:
Lenkeng LKV372AE
You can also buy extenders with a set of removable brackets that can be attached to the surface of your choice with screws. Perhaps this is a successful combination of the first two options.
Lenkeng LKV676E
Lenkeng LKV676E Lenkeng LKV676E Some manufacturers offer additional rack mounting brackets for transmitters and receivers. But this is often offered with expensive professional equipment. Courtesy of Kramer Instead of conclusion
Professional installers have found their own ways of mounting the kits. They use double-sided tape, ties, or other methods. I agree that some sort of life hack can always be found. But at the same time, i want to draw your attention to the variety of devices that are meant for specific applications. I also want to point out that sometimes manufacturers try to facilitate the subsequent installation of their products and that is why they really deserve a special thanks.
The LED strip is mounted on a vertical heat sink and emits light sideways. The detector/sensor is 1 foot away from the strip.
I measured the illuminance with my new high-precision instrument - spectral & illuminance analyzer HOPOOCOLOR OHSP-350MF. Total accuracy of illumination ±4% (for 1000 FC).
By comparison. My old lux meter (good quality) has an accuracy of ±3% rdg ±3% f.s. What does this mean? For measured value 1000 FC: ±3% rdg = 3% of 1000 FC = 30 FC ±3% f.s. = 3% of 4000 FC (full scale) = 120 FC Total = 150 FC = 15$ strong for 1000 FC.
Many manufacturers don’t specify full-scale accuracy. Their instruments will appear to be very accurate.
Measured values
I measure the illuminance every time I decrease the voltage by 0.1 V. The values obtained have some scatter, related to the instrument accuracy, the measurement method, and other details. I additionally introduced a trend line to simplify the perception of the results.
Also, for simplicity, I made additional calculations of the relationship between illumination and voltage (in %).
Conclusions
1. The change in supply voltage has a linear effect on the change in light emission from modern LEDs and assemblies.
2. The light emission change from the supply voltage depends on the LED type and strip design (LED connection scheme, section length, resistors, etc.)
3. The light emission from the LEDs decreases faster than the supply voltage decreases. My samples of LED strips with voltage supply showed the following results: 3a. 2216 chip strips: 5% voltage = 20% illumination and 10% voltage = 40% illumination 3b. 2835 chip strips: 5% voltage = 12% illumination and 10% voltage = 26% illumination 3c. COB low power strip: 5% voltage = 36% illumination and 10% voltage = 70% illumination.
Warning. Other strips will give different results.
4. Incorrect connection of long LED strips to the power supply will significantly reduce the level of emitted light (due to the high self-loss on the LED strip conductors). (see conclusions to the post “Why 24V LED strip is better than 12V?” Catastrophic effects will be for powerful low-voltage (5-12V) LED strips.
What makes up a cable locator receiver? Which sensors are used in receivers? What is the purpose of the different types of sensors and various combinations of sensors used? How does one correctly orient the receiver to the cable being traced?
There are generally two types of sensors used in cable locator receivers: a whip antenna, also called a pole antenna (capacitive sensor), or a coil (inductive sensor). The design of a single receiver may include one or two different types of sensors. However, there are many kinds of sensors and they can be used in various combinations.
The receiver filters, amplifies, and processes the signal from the sensors and outputs it to the operator so that a decision can be made. The simplest receivers only generate an audio signal the volume of which is proportional to the level of the received electromagnetic signal. In some simple receivers, the audio signal is also supplemented by a light indicator, which further helps establish the level of the received electromagnetic signal. Obviously, these kinds of simple receivers will allow you to get reliable results only in simple cases. Their main advantages are their ease of use and low cost.
Conversely, more complex models use digital signal processing, as well as one or more sensors. Complex receivers are not limited to detecting signal strength. They can also interpret other data, such as the signal current voltage in the cable being traced, the cable depth, the direction in which the cable is located, etc. Such receivers also have multifunctional displays with an easy-to-read representation of the corresponding signal information. However, only an experienced operator that is trained to use such devices will be able to use a complex receiver effectively.
The design of the receiver depends on the purpose of the cable locator. There are several locator designs available for those used to detect underground cables or pipelines, overhead cable lines, cables in buildings, and so forth. The monoblock design is the most common. When it comes to the monoblock design, the sensors, all of the receiver's electronics, controls, and displays are housed in a single solid casing. Work in hard-to-reach places or at high elevations is often performed with the help of extended remote sensors. These sensors are sometimes attached to a boom. The monoblock design is also almost always implemented for complex receivers where several sensors are utilized simultaneously.
Most compact hand-held devices implement a whip antenna. These types of devices are usually used inside buildings. The whip antenna can be made of either a special plastic or a conductive material. In the former case, it provides safety when working on live power lines, and eliminates the possibility of accidentally short-circuiting uninsulated contacts or cable cores. In the latter case, the antenna can also be used as a contact probe, which is very convenient when working in high mounting density conditions, such as on the crossbar (MDF) or patch panels.
If the receiver has a whip antenna, the maximum signal strength is applied to perform the tracing. The most convenient way to perform the tracing is to zigzag the antenna along the line being traced. When the antenna passes directly over the cable, it will detect the maximum signal strength.
The axes are arranged vertically or horizontally in coils that are used as the inductive sensor. The electromagnetic field lines of the signal-carrying cable penetrate the coil differently, depending on the orientation of the coils. When the coil is passed over the cable, the magnitude of the induced signal changes. At the same time, the coordinates of signal maximums and minimums depend on the orientation of the coil.
If the coil is positioned horizontally, the maximum induced signal will be directly above the cable and is detected by its peak value. This doesn't only happen because the receiver is closest to the cable at this point, but also because the axis of the coil...
Previously, we've reviewed several options for twisted-pair network cable HDMI extenders. We've also taken a look at their various functions. This time, i would like to focus on an interesting type of device: an HDMI splitter/extender via a twisted-pair network cable. To do this, i will be using the Lenkeng LKV714PRO as an example.
Main features and characteristics
What is the purpose of this type of device? There are cases when it is necessary to multiply the signal from one video source (TV-tuner, PC, video recorder) to several displays. If these displays are so close to the source that you can reach them with a regular HDMI cable, then it would be best to use some kind of special HDMI splitter. There are so many of them available on the market right now. You have the option of going from 1 to 2, or 1 to 8, or even 1 to 16. That is, one HDMI input is multiplied to 2, 4, etc. outputs.
However, it's a different story when all the displays are far away from the source and you can no longer use a regular HDMI cable. In this case, there are two solutions.
The first way is to use an HDMI splitter for the desired number of outputs and then connect the required number of HDMI extender sets to the outputs via twisted-pair network cables. An example of a wiring diagram for such cases is as follows:
There is nothing wrong with this solution except for the huge amount of wires, transmitters, and power adapters on the splitter side.
So what can be done about this problem?
There are plenty of manufacturers that make devices that combine an HDMI splitter and the required number of HDMI transmitters over twisted-pair network cables. As a prime example, Lenkeng sells the LKV714PRO as a set with 4 receivers.
Thus, in our case, i replaced the combination of an HDMI splitter plus 4 transmitters and the accompanying wires between them with a single small box that has an HDMI input, an HDMI output for the local display (link to the article about HDMI loop-out), and four RJ45 outputs for connecting the twisted-pair network cables.
Now our wiring diagram looks like this:
External inspection
The set consists of:
- combined HDMI 1 to 4 splitter with twisted-pair network cable transmitter and power adapter
- HDMI via twisted-pair network cable receiver - 4 units
- IR blaster extension cabe
- IR receiver extension cable - 4 units
Splitter/Transmitter
The combined splitter/transmitter device is relatively compact in size. The case includes the minimal set of ports that serve their declared purpose, namely the HDMI input used to connect the video source and four RJ45 connectors for the twisted-pair network cable connection. As a pleasant bonus, the housing has built-in wall-mounting flaps to easily affix the devices to flat surfaces.
Conveniently, there is also a loop-out HDMI output for connecting a local TV (in this article i looked at what this is and what it's for).
As a side note, i would like to mention that there is also a DIP switch installed in the device for adjusting the requested EDID at the video source, which can be useful if the installation calls for the simultaneous use of different types of TVs. For example, one of the TVs in the setup may not support 1080p 60Hz 7.1CH audio (maybe it's some old projector). In this case, the switch can be used to select a video and audio format that is compatible with all the display devices.
There is also a port on the housing for connecting the IR emitter that comes with the set. This set supports reverse IR signal transmission (pass-back) from the TVs to the receiver. I discussed this functionality in more detail in this article (link).
If you remove the cover, you can immediately appreciate the thickness of the steel housing. It's quite impressive. The quality of the soldering is also relatively high. You can also notice another impressive component once the cover is off, which is the heatsink that's installed over the chip responsible for the video transmission via the twisted-pair network cable....
If you drive a car, it's very likely that you've come across an uncomfortable situation involving a cyclist at least once or twice in your life. Bikes can be quite unpredictable on the road and you often have to guess what maneuver they'll pull next. Electrically-powered bicycles and scooters are especially erratic when it comes to sharing the road. And once it gets dark out, the situation worsens twofold.
Recently, I started dabbling in electric biking myself. However, I would say that factory reflectors on it aren't the best way to make your electric steed easily noticeable on a bike path. Therefore, it's time to unholster my trusty soldering iron and make this world brighter put together some LED turn signals.
I really like the dynamic LED turn signals that come pre-installed on some modern cars. I wish I had something like that on my bike. The most obvious solution would be to use an Arduino and LEDs with a WS2812 chip. Nowadays you can find a microcontroller with its own firmware in something as mundane as a teapot and no one would be surprised by it. However, the fact that this can be realized by just using some "hard" logic and without a microcontroller can really leave some modern electronics engineers scratching their collective heads. Unsurprisingly, that's exactly what I found myself doing when I came across the "RF74xxID The Multifunction Passive 7400 RFID Tag" project on the interwebs.
At the time I was so absorbed by microcontrollers that I didn't even think about the fact that just a couple of decades ago, electronics engineers somehow managed to get by without them, and even launched rockets into space.
Anyway, at some point this became an obsession for me, and I decided to design a dynamic turn indicator circuit using only 7400-series integrated circuit. And with that, I welcome you to dive a little bit into retro electronics with me.
The proposed dynamic turn indicator control circuit doesn't involve any expensive or scarce components. It's easy to reproduce and it works immediately after assembly (if everything is soldered properly).
The circuit lights the LEDs in a strip one by one immediately after the power supply voltage is applied to the J1 connector. Once all the LEDs are lit, they will continue to stay lit as long as the power supply voltage is present. If you power this circuit from a car turn signal relay, you get a dynamic turn signal effect as a result.
The speed at which the LEDs in the strip gradually light up is set with the RV1 variable resistor at 50kΩ. Thus, you can pick a speed that's to your liking. At the maximum resistance of the variable resistor, all 8 LEDs will light up in about 0.6 seconds after power is applied. You can choose a position for the resistor that makes all the LEDs stay lit for a little bit after the strip is fully powered, but that's up to you. If your turn signal relay flashes once per second, you can replace the RV1 variable resistor with a regular 43kΩ resistor.
The standards for rear turn signals are a bit of a mess right now. On some cars they're red, while others have yellow ones. Therefore, the selected R1-R8 resistors are for red and yellow LEDs with an operating voltage drop of about 2.2V. The operating current should be about 10mA. But remember that the maximum output current for the 74HC164 per output is 25mA. This value should not be exceeded. Choose whichever turn signal color you like more.
If you believe that 8 LEDs are too many for your liking, you can reduce their number down from the bottom to the top, i.e. first remove D8, then D7, and so on until you have the desirable number of LEDs left.
Conversely, if 8 LEDs aren't enough, you can safely scale this circuit without any problems or catastrophic price spikes. All you need to do is add the necessary number of shift registers, as shown in the following diagram.
The high output of the first shift register is connected to the data input of the second register. You can also...
How does one determine the direction and strength of the current of the probing signal? What does the information about the current of probing and induced signals provide? Which techniques allow the most accurate determination of the cable's depth? How does one take the influence that induced signals have on neighboring cables into account?
Complex locator models don't necessarily just have receivers with different types of sensors, but can also have receivers with several sensors of the same type. For example, two horizontally-oriented inductive sensors (two coils) provide a great deal of extremely useful information with the help of signal processing, which considerably facilitates the tracing process. In this case, the information refers to the power of the probing signal current, its direction in the cable being traced, and the depth of the cable. Also, all these additional functions are only used for tracing in active mode, or when the line signal is fed from the signal generator.
The necessary cable can be easily identified among other nearby cables that also carry the induced signal if the direction of the current and its power can be determined. This is possible because the direction of the carrier current and the induced current always oppose one another (the signal current flows from the transmitter and the induced current flows to the transmitter). Additionally, the signal current in the cable being traced is always more powerful than the induced currents in neighboring cables.
The ability to determine the power and direction of the current allows you to confidently identify underground cables that run in parallel but at different depths. The carrier signal that the receiver detects from a deeply buried cable being traced is often significantly less powerful than the induced signal from a cable that runs at a shallower depth.
Aside from this, determining the current strength allows you to detect taps and assess the condition of the cable insulation. The current value gradually drops due to signal leakage to ground as it moves along the cable being traced. If the value changes intermittently, this signifies a tapped cable or a defect in the insulation. The detection of a second signal source with the same current direction (from the generator) indicates a tap. Other cases of intermittent signals indicate an insulation defect.
If repair work is being carried out in high-density conditions, where multiple communications are nearby, it is very important to perform cable tracing with a receiver. A cable receiver can estimate the depth of all the lines that pass in the vicinity with high accuracy. A device with two coils does this with the help of internal mathematical processing of two signals, which it receives from two sensors (the sensors are located at different heights inside the device). The amplitude of the induced signal depends on the distance to the source, so the depth can be calculated using a simple formula.
However, the same result can be achieved even when using a receiver with a single inductive sensor. The following simple algorithm can be used to do this:
Make a mark directly above the cable on the ground (using the peak or zero value of the received signal);
Turn the sensor at a 45° angle relative to the ground and, while maintaining this angle, slowly move it away from the cable being traced;
The signal volume will decrease to a minimum and then increase again;
It's necessary to mark the point at which the signal level was at its minimal;
The depth of the cable will be equal to the distance between the two points marked on the ground.
However, magnetic field lines can be distorted by other conductors nearby. The first sign that this is the case is a change in the location of the maximum or minimum signal when the coil sensor is at different heights. An imaginary line passing through certain points indicates the more likely position of the cable. The exact position can be determined after assessing the cable's...
When buying an HDMI extender over a twisted-pair network cable, it's possible to inadvertently buy a kit that isn't quite what you were looking for. You see, these extenders can be divided into two types:
1. Extenders that send a signal solely via a "direct" twisted pair network cable 2. Extenders that can send a signal either via a "direct" twisted pair network cable or a LAN (Local Area Network)
The former type of extender uses a twisted pair network cable to transmit a direct signal between the transmitter and the receiver. This type of device cannot be connected to a LAN. These devices work by using the given manufacturer's in-house created protocols, or by using the rather popular HDBaseT technology. HDBaseT technology makes it possible to "link up" devices from different manufacturers (for example, an HDBaseT receiver can be pre-installed in a projector).
Typically, all extenders of this type transmit video and audio without delay or loss in quality. The range for these devices is typically either 230 or 330 feet. The connection type is called "point-to-point".
I connected the Lenkeng LKV372AE-4.0 kit for a hands-on demonstration. It allows for an HDMI signal transmission over a twisted pair network cable of up to 230 feet. I connected a technically remote monitor to a laptop using this kit, duplicated the screen, and started the timer. I took some photos with a shutter speed of 1/1000 to avoid blurring the values at thousandths of a second. The photos show that the signal transmission goes through without any video delay.
The latter type of extenders can also work through a Local Area Network (LAN). And just like the former type, the receiver and transmitter can also be connected with a twisted pair network cable or you can send the signal through an existing LAN via a router. In this case, the transmitter and receiver get assigned some IP addresses.
Transmission ranges. By connecting the transmitter to the receiver with a twisted pair network cable, you can achieve a transmission range of 330-390 feet. Some manufacturers boast a range of 660 feet, but at a lower resolution. If you connect through a router, the range will increase from 330 feet to "330 feet - router - 330 feet".
Image quality and latency. Since the classic IP protocol is used in this case, the video is usually sent encoded as a MPEG-4 or a similar codec. This means that the quality will slightly be affected due to compression. When watching movies or TV, you probably won't experience a decrease in quality. When transmitting a computer's desktop, there may be a barely noticeable moiré effect near the letters and numbers in some programs. There's also a slight delay, which becomes noticeable when moving the mouse pointer around on the desktop. . A slight lag in the movement is present.
I prepared a setup with a Lenkeng LKV383-4.0 HDMI extender, which I connected through twisted pair network cable without a router. I started the timer and took a few photos at 1/1000 shutter speed. I timed the latency at 0.064 seconds. This is relatively small. However, you can feel it when you're working with a mouse, which may cause some discomfort. If you use the extender kit via a LAN that has other devices on it, the latency will definitely increase.
In other words, when watching TV and video, or if the mouse is rarely used, this inconvenience is negligible.
I would like to note that many manufacturers have special types of LAN extenders in their lineups that transmit uncompressed video. This results in original-quality video (without compression) and minimizes the latency to nearly zero. However, such devices require a 10-Gigabit network that is isolated from additional devices. On top of that, their cost is multiplied many times over compared to the devices i tested.
She's in love with electronics, guitars, and cats.
/ Kevin (teardownit.com editor) /
ANOTHER secret helper. This guy can't write posts.
We will consider the principles of how a step-up (boost) converter operates, and most importantly, current and voltage feedback, using a homemade LED flashlight as an example.
Pulse power converters (or voltage converters, as they are generally called) have long been an integral part of electronic technology. The fact of the matter is, chemical current sources such as batteries and accumulators produce low voltage, while many other devices, primarily those based on vacuum and gas-discharge lamps, require high voltage.
The basis for today's DIY kit is the ready-made ICSK034A from icstation.com. This is a kit for assembling a 5 to 12 volt step-up converter.
This isn’t just a joule thief, but a stabilized converter that maintains a predetermined voltage at the output. However, my goal today is not to make a 12V power supply, instead, I want to make an LED flashlight with continuously variable brightness. In other words, I’m going to make a controlled boost current regulator for the LED.
So, today we are going to study the feedback of pulse power converters and as a result, we will be able to build a converter with the properties that we need. Or we can modify an existing converter to the one we need, specifically, one where we can add or change the current or voltage feedback. Or we can make the existing feedback controllable, i.e. add the possibility of reconfiguration.
The main component of a step-up converter is the coil. In electronics, coils and capacitors are called reactors because there is a reaction, i.e., a counteraction.
Converter operating principle
The step-up voltage converter works as follows. The power consumer is connected to the power supply through a coil and a diode. If nothing happens, the voltage at the consumer is equal to the input voltage minus the drop on the diode and the coil's active resistance.
But after the coil, there is a switch that closes the circuit, which consists of the power supply and the coil. In a real converter, this would be a bipolar junction transistor (BJT) or a field-effect transistor (FET). This can also be a separate transistor or one that’s integrated into a chip.
When this switch closes the circuit, the current in the coil increases. The active resistance of the coil is usually low, so it should be turned on briefly so as not to burn anything out.
When the switch breaks the circuit, the coil tries to keep the current constant. Now there is no path for the current to take through the switch, so it will go through the diode to the power consumer instead.
When the circuit of the switch is opened, the current decreases. At the moment the current decreases, an electromotive force (EMF), i.e. voltage, is generated in the coil. Its polarity causes the current to flow in the same direction as it did when the switch was turned on.
That is, this additional voltage is added to the EMF of the power source. Therefore, the power consumer receives more voltage than the original source provides. This is the reason why this type of converter is called a “boost” converter.
The capacitor smoothes out voltage spikes in parallel to the power consumer. When the coil generates an electromotive force, it is charged to a higher voltage. When the coil is charged with current through a switch, the capacitor gives the stored charge to the power consumer.
These two reactors, or integrators, the coil, and the capacitor are integral parts of the step-up conversion process and are mandatory components of the converter.
How is the generator connected? How to choose the right type of receiver probe? How to provide a probing current in the line being traced? What affects the range of the locator?
A thorough knowledge of all the techniques of working with the device, of course, does not guarantee error-free results (statistics show that even a very experienced operator during the day can make 10 to 20% of the errors in the total amount of work), but it can reduce the number of miscalculations.
The main tasks that can be solved by the cable locator :
Determination of the cable route (cable bundles) and cable ducts;
Identification of cable lines in a bundle or cable ducts, among others running in parallel;
Identification of cable terminations;
Cable core identification.
Solving each of these problems may require an individual approach - it all depends on the type of line being traced (twisted pair cable, coaxial, power, cable duct, pipeline), its characteristics (cross-section, frequency properties, length), its location (on the surface, in a cavity or in the body of a monolithic building structure, in the ground), as well as the characteristics of the generator and receiver available. Therefore, giving a set of direct and unambiguous instructions is impossible. A system of preferences, however, can be described.
First, you must determine the most effective sensor type for the case in question (coil or capacitive antenna) and the method of signal delivery (direct connection or inductive method).
Direct connection involves physically connecting the transmitter to the line you are looking for, which requires access to either the cable strands or the surface of the conduit (conduit), and provides a rich selection of signal circuitry. In addition, it provides the most powerful signal applied precisely to the desired circuit. Therefore, if direct connection is possible, it should be preferred. The exception to this is when the line is energized. Although the transmitter output is normally protected against AC voltage up to 120 V, it is not advisable to connect it to live cable conductors. In this situation, an inductive coupler or inductive antenna is better suited.
An inductive sensor offers much greater capabilities than a capacitive sensor. However, to use a coil, the signal must be applied to a closed circuit through which sufficient current can flow for the available receiver sensitivity.
If we are talking about two conductors of a cable (a pair of cores or a core and a shield), there are only two cases where such a circuit can be arranged. First, if the remote end of the circuit is accessible and the conductors to which the signal is applied can be shorted. Second, if it is loaded (for example, the conductors are connected to a load or to the input circuits of some equipment). This also applies to pairs of conductors shorted due to reduced insulation resistance.
A closed circuit can also be arranged with a single conductor (core, shielding, metal armor, or a central supporting element of the cable, a conductive cable duct). This requires that it be connected to an earth bar at the remote end. This method is only suitable for lines within the same building (structured cabling, fire alarm, and power supply) because the generator must be connected to the same conductor and ground busbar.
It is crucial to understand that the range over which the receiver will be able to detect the signal depends to a large extent on the purpose and design of the cable. Since one of the goals of most cable designs (especially high-frequency cables) is to minimize the emission of the transmitted signal, selecting the conductors to which the signal will be fed must be made with great care. Tracing cables in a shield or protective covering (sleeve, wire, or foil braid) is possible because they do not eliminate the magnetic field completely. The signal is much more attenuated in cables armored with a steel tape or wire. It is almost entirely blocked by cable ducts made of steel or...
The power supply is based on the MP023 chip. It is a one-cycle DC-DC controller created by Monolithic Power Systems in 2016.
Schematic: Input → filter → bridge rectifier → flyback converter with rectifier working for the output C-filter.
From the converter output, the voltage comes to the PWM modulator unit based on the Silicon Labs EFR32 "Wireless Gecko" module.
Luminaires are connected to the modulator output via the output connector.
The marking on the power supply case: λ>0.8, and the coefficient value hints at a passive corrector.
The radio elements are assembled neatly. The circuit board has no electrical defects, and the connection quality is good everywhere.
Test results
• The pulsation value as a fraction means that the voltage has pronounced HF (numerator) and LF (denominator) components.
• The hottest component in the power supply is the output rectifier diode. The measurement is taken with the cover removed.
• The overcurrent protection is triggered at an output current of 1.3A, first limiting the current; then, when the voltage drops to 17 V, it goes into start-stop mode.
Output voltage pulsations
Slow sweep waveforms
Fast sweep waveforms
Conclusions
• This power supply has a high level of output voltage ripple. If it were not for the built-in wireless control module, this power supply would be trashed. BTW, if you want to reprogram the wireless control module, check out the articles here (in new tab) and here (in new tab).
• The element heating at full load and with the cover off is 154 F, which gives some reserve.
• This type of power supply cannot be paralleled for a load greater than the rated load of one of them.
It should be noted that there is a slight overshoot; increasing the load slightly increases the output voltage. Power-on parameters Powering on at 100% load Before testing, the power supply is turned off for at least 5 minutes with a 100% load connected.The oscillogram of switching to a 100% load is shown below (channel 1 is the output voltage, and channel 2 is the current consumption from the grid):
As children, many of us had an NES (Nintendo Entertainment System) game console. Its gamepad had 8 buttons: a plus-shaped button for left, right, up, and down, then Select, Start, A, and B. And there were only five wires in the gamepad cable: ground, +5-volt power, and three signal wires. Meaning the state of eight buttons was transmitted over three wires.
Output voltage under a constant load
The high stability of the output voltage should be noted.
For successful direct fault detection, two parameters are of particular importance. First is the maximum distance to the damaged spot when it can still be clearly identified. The second is the accuracy of determining the defect.
To determine the distance to a particular fault spot or just an impedance abnormality of the cable, one needs to simply set the propagation coefficient and measuring range. The propagation coefficient defines the speed of the electrical impulse going through the cable of a particular type as a reference for the reflectometer. After capturing the impulse, the device will automatically calculate and display the distance to the damaged point of the cable.
When a harmonic signal circulates in a twisted pair circuit, the voltage-to-current ratio at each point is called the input impedance of the twisted pair. If a twisted pair is loaded at the end with a resistance equal to
Some soldering sloppiness never hurts, but we had to point this out.
If you are unfamiliar with the binary numeral system, it's high time to learn it. It is precisely the same as the decimal we're used to; its base number is 2 instead of 10.
The SN74HC161N chip has a 4-bit input P0..P3 and a 4-bit output Q0..Q3, a carry flag output, a CLK clock input, and four control inputs.
Features
However, the idol of millions, Kurt Cobain, the author of world-favorite solos John Frusciante, and electric guitar classics Steve Vai and Joe Satriani either did not know that the BOSS DS-1 sounds terrible or managed to make it sound good.
