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• End Piece with Wire tensioner

  Florian B. • 15 hours ago • 0 comments

  Sometimes it can be difficult to apply tension to a wire. So I created a very practical end piece:

  The wire is clamped into the center of a moving block that has a M10 thread on the outer side.

  With a hex nut the block can be moved outside to apply tension to the wire.

  Magnetostrictive Position Sensor
  

  
  

• Multi Pulse Time Measurement Unit

  Florian B. • 6 days ago • 0 comments

  Here is now another time measurement device built with conventional TTL-Hardware.

  Idea is to provide an understandable circuit without exotic hardware such as a CPLD.

  The device works excellent and I prefer it to the measurements with Arduino-Uno.

  It can measure up to 16 pulse time values a 16 Bit.

  Here how it works:
  

  The Measurement is engaged by setting EN (and nCLK) to High, Then the Channel is selected with CHSEL and an Excitation Pulse is triggered (TRIG).  

  The TRIG signal resets the 74LS193 index counter adressing the Storage cells.

  With a delay Monoflop CD4089 the TRIG signal is delayed to reject Signal impulses coming directly after the excitation.  

  The delayed Trigger signal resets a RS-Flip flop and clock pulses are fed to the synchronous 74LS161 counters.

  The negative Signal of an incoming Signal stores the acutal counter values into 4-Bit 74LS198 TTL-Rams addressed by the index counter.

  The Signal pulse increments the index counter. When the counter overruns the Carry will stop the  measurement by setting the RS-Flip-Flop which disables the time measurement counters are disabled.

  The counter can also be stopped by the Microcontroller by setting EN to LOW to terminate measurement when less than 16 signals are registered.

  Now the Microcontroller can read out the values by decrementing the index counter with nCLK, observing BO which indicates a Zero-Transition as a LOW value.

  Each counter value is read nibble by nibble addressing it with A,B. The nibble values appearing at A0..A3. Microcontroller has to invert these values because 74LS189 is inverting the values.

• New Exciter with Gate-Driver

  Florian B. • 02/15/2025 at 22:51 • 0 comments

  Direct driving the Mosfet  from the CMOS-Monoflop is not optimal as the capacity of the gate deteriorates the pulse somewhat. It seems that the usual way would be to use a gate driver IC. But before ordering one I wanted to try it out first with a discrete circuit from Mr. T's: 3 Simple MOSFET Drive Circuits
  

  I opted for the "Cascode-Driver", which works very well in my case. It also works for a High-Side P-Channel Mosfet when changing npn to pnp transistors, reversing the polarity and driving the circuit using the non inverting Output of the Monoflop.
  

  Additionally I also added a small resistor in series with the wire to decrease the impulse load of the power supply.
  
  
  

• Signal Quality and new Magnet cursor

  Florian B. • 02/09/2025 at 20:23 • 0 comments

  A new magnet cursor for stronger signals:
  The signal quality depends on several parameters:

  
  

  Diameter and Material of the Wire

    I only checked Ni and NiFe wires. Ni wires seem to work better.

  
  

  Permanent Magnetization of the wire

    Ni wires can be permanently magnetized which can lead to errornous signals.

    Especially the region near the reciever coil should be magnetically "clean"

  
  

  Clampings of the Wire:

    Hard clamps generate reflections,  soft (rubber) clamps suppresses reflections. 
  

  
  

  Exciation Voltage

    The signal strength depends on the excitation voltage.

    Values between 10V and 20V are ok. In my setup higher voltages are not recommended due to the driving CMOS IC.

  
  

  Duration of Excitation

   The longer the signal the higher the signal.

   However longer excitations generate mutliple wave trains.

   Goal is to have only a "wavelet" with one prominent peak.

  
  

  Cursor Magnet orientation and strength

    stronger magnets can create larger signal amplitudes. But also the orientation of the magnets are relevant.

    I achieved best results with Nd-magnets positioned around the tube with magnet poles showing in the same direction  namely towards the wire. The pucture above shows the new magnet holder for up to 6 4mm Nd-Magnets.

  With three magnets loaded and damping at both ends I am getting a very strong and clear single wavelt pulse. The relfection (right) is below the comparator threshold:

  
  

  Receiver Coil

   Number of windings of the reciever coil. The more windings the larger the signal. However with larger number of turns  also the direct response of the excitation signal prolongs. I am using 700-800 Windings. But I will check if  1000 Windings will yield a better signal.

  
  

  Amplifier Circuit

   The amplifier is critical. Especially the RC filter between the first and the second Amplifier stage is critical.

  
  

  Comparator Circuit

   Adding small hysteresis by a feedback resistor to the + input will suppress ringing oscillations

• Time Measurement with Arduino UNO (ICP and Timer1)

  Florian B. • 02/08/2025 at 19:18 • 0 comments

  A convenient way to measure the pulse times can be accomplished with Arduino UNO's Input Change interrupt of Timer1.
  With this method no extra counter hardware or a CPLD / FPGA is required. 

  The Counter of Timer1  is captured when a pulse is detected at a specific input, namely Pin D8. This limits the usage of this method a bit with the traditional Arduino Motor shields which utilize this pin for Motor Break. 

  Howver for the I2C controlled Quad-Motor shields such as Adafruit Motorshield V2  this is no restriction.

  Description:

  Time Measurement with Arduino UNO's TIMER1 and Input Capture on Pin 8 Signal containing negative Start and Stop pulses (High->Low) 

  --      ----------------------------  ---------
    |    |                                 |  |
    -----                                 ---
    Start (TRIG=Trigger)       Stop (SIG=Signal)
  

  Time measurement takes time between Start and Stop pulse.

  Direct after Trigger the Excitation pulse generates an immediate response with lots of unwanted SIG pulses which we need to skip. The usual time in my setup are 40us. In my first attempts with software delays I observed some jitter. Therefor I decided to introduce a Hardware Delay with a CD4098 Monoflop. This is the Delay Gate Circuit which is introduced in the Build Log.
  

  The Monoflop is simultaneously triggerd with the Excitation Pulse (TRIG).  This delayed inverted Trigger signal nGTRIG is combined with the Raw signal SIG from the Amplifier/comparator with a logical AND:

       nGTRIG and SIG

  Ideally we will get one nGTRIG signal and one or more SIG.
  .

  Signals
  SIG                                                               active Low      Raw signal form Amplifier / Comparator
  TRIG            D4                                            active High      (SEL1) Triggers Excitation Circuit and Delay Gate
  nGTRIG                                                        active Low      Delayed Trigger Pulse
  SIG'             D8                                            active Low      SIG = GTRIG and SIG                                

  For more position sensors we can introduce a 2:1 Multiplexer which is controlled by:

  CHSEL        D9 (Channel select 0 or 1)      (CHSEL) Selects Measurement Channel

  Setup of Timer1:

  /*
   * Setup Timer1 for Input Capture 
   */
  void setupTimer1()
  {
   
    // Input Capture setup
    // ICNC1: Enable Input Capture Noise Canceler
    // ICES1: =1 for trigger on rising edge
    // CS10: =1 set prescaler to 1x system clock (F_CPU)
    TCCR1A = 0;
    TCCR1B = (0<<ICNC1) | (0<<ICES1) | (1<<CS10);
    TCCR1C = 0;
  
    //catchFallingEdge(); // initialize to catch
     TCCR1B &= ~(1<<ICES1); TIFR1 |= (1<<ICF1);
    // Interrupt setup
    // ICIE1: Input capture
    // TOIE1: Timer1 overflow
    TIFR1 = (1<<ICF1) | (1<<TOV1);        // clear pending
    TIMSK1 = (1<<ICIE1) | (1<<TOIE1);   // Enable Timer OVF & CAPT Interrupts
    
    // Set up the Input Capture pin, ICP1, which corresponds to Arduino D8
    pinMode(8, INPUT_PULLUP);
  }

  We then...

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• Basic Magnetostrictive sensor

  Florian B. • 02/07/2025 at 15:38 • 0 comments

  To build a Magnetostrictive sensor rig you do  not need much. A wire clamp and eventually a wire tensioner, a coil and a moving magnet are enough. Of course you need the electronics described above. Here as damper a wine cork is used.
  Coil, magnet holder and tensioner can be found here: Parts for Basic Magnetostrictive Position Sensor
  
  

  In this configuration stronger damping is established. Here no quartet pulses are seen but solely the main pulse. With this setup the readout is very easy as only one puls has to be evaluated. However in this setup the position determination works only if distance of manget to coil is larger than 7cm.
  

• Time measurement with CPLD

  Florian B. • 02/07/2025 at 13:30 • 0 comments

  Time measurement with CPLD

  My initial approach for time measurement was to utilize the Input capture feature of the Arduino UNO's timer1.

  Another option to measure the time is by utilizing a CPLD. With this I can measure up to signals of up to 4 signals. We can apply digital delays and signal debouncing. I am using an older but hobbyist friendly 5V tolerant and thus "Arduino compatible" EPM7128SLC84-15 for this. This device limits the acquisition to 4 Pulses with a maximum time count of 13 bits. With a more powerful device more bits and more signals can be measured but for my experiments this is just enough.

  The following VHDL code implements such a time measurement counter.

  A measurement is initiated with a High-Low-Transition of the TRIG Signal. This event will start a Time Counter. that is clocked with externally provided 16MHz clock pulses at COUNT_CLK. After a time delay it accepts Low signals at input SIG and records the time. Up to 4 signals can be measured with a resolution of 13 bits.
  

  The Arduino reads the counter value in chunks of 4 bit nibbles adressed by A0 and A1. The data is available at the Data port D0..D3. Before the first read out READ_RES is set to Low and a negative Clock pulse is applied at READ_CLK. After all nibbles are read the read counter can be advanced by setting READ_INC to High and applying another READ_CLK pulse. Values are combined in the Arduino sketch.

  Signals are:

  -  COUNT_CLK   - Input for external clock Into CPLD
  

  -  TRIG                 - Input for Trigger pulse
  

  -  SIG                   - Input for digitized Signal pulse
  

  -  READ_CLK      - Clock Input for read interface
  

  -  READ_RES      - Reset Input for read interface (to reset to first measured signal)
  

  -  READ_INC      - Increment Input for read interface (to advance to next measured signal)
  

  - A0, A1               - Nibble select input to select the counter nibbles
  

  - D0,D1,D2,D3    - Data output port to transmit data to the Arduino
  

      library IEEE;
      use IEEE.STD_LOGIC_1164.ALL;
      use IEEE.NUMERIC_STD.ALL;
  
      library IEEE;
      use IEEE.STD_LOGIC_1164.ALL;
      use IEEE.NUMERIC_STD.ALL;
  
      entity TimeMeasurementCounter is
           generic (
              data_width : integer := 13
           );
           Port (
                COUNT_CLK : in STD_LOGIC;                -- 16 MHz clock for time measurement
                READ_CLK : in STD_LOGIC;               -- Clock signal for micro controller read out
                READ_RES : in STD_LOGIC;               -- READ_RES='0' + one READ_CLK resets read counter
                READ_INC : in STD_LOGIC;               -- READ_INC='1' + one READ_CLK incements read counter
                TRIG : in STD_LOGIC;                   -- start the measurement
                SIG : in STD_LOGIC;                         -- signals 1-0-Transition to be measured
                A : in STD_LOGIC_VECTOR (1 downto 0);  -- Nibble address 
                D : out STD_LOGIC_VECTOR (3 downto 0)  -- DAta port for nibble
           );
      end TimeMeasurementCounter;
  
      architecture Behavioral of TimeMeasurementCounter is
           signal TC : STD_LOGIC_VECTOR (data_width downto 0) := (others => '0');     -- Timer Counter
           type reg_array is array (0 to 3) of STD_LOGIC_VECTOR (data_width downto 0);  
           signal  R : reg_array := (others => (others => '0'));              -- Register for measured times
           signal  RC : STD_LOGIC_VECTOR (2 downto 0) := (others => '0');     -- Index for registration process
           signal  RC2 : STD_LOGIC_VECTOR (1 downto 0) := (others => '0');    -- Index for readout process
           signal  sig_state: STD_LOGIC := '0';                               -- state is 1 to indicate that a signal was registered
                                                                                                    -- will go back to 0 when SIG gets back to 1
           constant DEAD_TIME : INTEGER := 80;                                -- Pulses registered after 40us * 16MHz
           constant DEGLITCH_TIME : INTEGER := 250;                                -- Pulses registered after 40us * 16MHz
   signal TCOLD : STD_LOGIC_VECTOR (data_width downto 0) := (others...

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