The 3 transducer model has proven game changing up to 90F & the transducers haven't died from being run continuously, so work began on a better enclosure.
3D printed enclosures this big are real expensive, so it was back to coroplastic & duct tape.
So the high voltage lines cause the water level sensor to fail high. They have to be separated.
The print statements in the interrupt handler cause PWM to fail even though they're not blocking. Such things happen at 1.25 MIPS. Lions have a strange fascination with running their micros as slowly as possible to use the least amount of power.
It pumps a lot of water with 3 transducers.
It proved easier to not use the switch & just power the thing off. There's a long delay for the ESC to start, but it's proven less hassle. All the software related to shutting down ended up worthless.
The amount of consumables used & the velocity of the water spray got lions wondering if a piezo rocket engine could be built. Anything kinetic is going to be far below ion engine efficiency, but would use a lot less power. It's too fragile to use as a fuel injector.
An enclosure is desperately needed. The mane needs are stabilizing it from falling over, catching overflows, adjusting height & angle. The best stability comes from routing the tube out of the bottom & sideways. The water level sensor still has to be vertical.
It is believed the existing PLA part could stay as it is & be attached to some kind of coroplastic stand. The PLA part needs a small overflow trap under it, with a way to pipe the water to another container. The best place for the electronicals would be behind the PLA part. The stand needs to be weighed down.
More height is better. Too low & it dumps water on the table. Too high & the monitor can't fit over it. Experience has shown it dumps a lot of water overboard. If anything gets in front of the transducers, a puddle soon forms.
No matter what lions do, the mist gets pulled down to the table. It probably needs a fan blowing up.
It could finally detect if the transducer was running by reading the LED voltage, then press the button by grounding the button. This allowed the mist to be controlled with a switch. The mane problem is the LED has to be debounced for 3 seconds, in case it flashes. If the switch is toggled too fast, it takes a few seconds for the transducer to match the desired state. Fortunately, the switch's physical position is always eventually matched by the transducer.
When the 5 minute timeout shuts it down, it senses the LED going out & presses the button to restart it.
The water level sensor was well & truly corroded after just 1 day.
The next step was gold plated copper. Helas, this still built up a layer of scale. The problem is the water level constantly rises & falls, depositing a layer of stuff every time. The hope is the resistance eventually levels off.
The 2 wire sensor had enough variability to detect a low & high level, allowing for hysteresis. A bigger reservoir with more room for overflow & longer wires would get better results from a 2 wire sensor but cost more.
The automated power button & level sensor were good enough to finally design a 3 transducer unit.
An unfortunate discovery was raising the gatorade bottle by just a little or putting too much water in was enough to cause the water to siphon out & flood out of the sprayer. It might actually be more effective to have a solenoid valve instead of a pump & gravity feed it.
These things arrived. They all worked, contrary to reviews. This model doesn't time out & doesn't detect running dry, but they don't seem to burn out.
Through hole soldering is still essential for an experimental design like this.
It worked, with all the misters being managed automatically.
Current draw overheated the voltage regulator after a few hours.
The cable management is a mess.
The only reason for keeping all 3 boards was to detect being out of water, but now that some models don't detect being out of water, it might be worth making a custom board to drive all 3 with 2 wires.
So the stock enclosure leaks when fed by a pipe, so a custom enclosure was needed. There are some pretty good commercial humidifiers which do the job for very little money.
Of course, there's no mention of whether they use a MEMS atomizer or a boiler. Ultrasonic, cool, & incompatible with essential oils are good indications of MEMS. With all the problems, it's almost not worth trying to duplicate a humidifier from scratch & probably going to cost more. They all use a gravity fed water tank. The outlet always points up.
There's not really enough room on the table to put a humidifier with much of a water tank anywhere. A pump made out of a hobby motor was to separate the water tank from the transducer, but it's really complex with a 2nd voltage & electronicals.
With the transducer removed from the stock enclosure, it was possible to document the inlet facing side.
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The lion kingdom's microscope game could be a lot better. It's still a webcam because it's hardly ever used. The holes were not visible from the outside at any magnification. There's no simplified explanation of how MEMS atomizers work, only a few chinese research papers. It appears to be just a titanium plate with holes etched in it. The smooth metal is where a photoresist once was. The acid created a rough surface around each hole.
The titanium plate vibrates rapidly. There's a film of water on the outside. According to kiwipedia, the vibration creates capillary waves on the outside. The capillary waves become too tall to support themselves & tiny drops fall off the tip of each wave.
There's no slow motion footage of a MEMS atomizer. It's not obvious why the mesh has to be a dome other than to show the user where the water comes out or to strengthen it.
After observing cracks forming on the outside, the mode of failure is believed to be work hardening of the metal over many hours of vibration. Eventually, it just cracks.
Custom enclosure #1 had a lot of leaks. The printer can't print smooth surfaces so the transducer couldn't make a water tight seal. The screw holes leaked. Facing up was definitely the best way to point it.
The best way to seal the screw holes was just to add glue where the water could leak out. Adding silicone grease under the transducer made a water tight seal against the uneven printing.
It worked for a few seconds after refilling the tank, then died until the tank was drained & refilled again. It was believed to be forming air bubbles under the transducer. Instead of floating up in the original side firing arrangement, they stayed in place until it died.
The vertical firing products obviously have more going on to feed the transducer than just dunking it.
Enclosure #2 solved the air bubble problem.
A new ESC didn't beep when the motor was off. Castles beep. Turnigies don't. This one required 7V.
The best way to detect water level was just measuring resistance.
Atomizing with the automatic water pump worked.
The next problems were manely with the water sensor. It needs 2 sensors to give it hysteresis. Otherwise, it constantly spins in stall mode while the ESC gets hotter & hotter.
The sensor needs to be securely farstened. If it falls off, it'll pump the entire gatorade bottle on the floor.
5V needs to come from the ESC so everything has 1 power source.
It needs a way to arm the water pump. The ESC has to detect idle speed when it comes on. If the ESC is turned off while the transducer is moving water out, there's no way to turn the ESC back on without turning off the transducer.
All the electronicals & the transducer should be self contained.
It's still fussy to get the transducer started. It still seems to get air bubbles. An automatic button presser to defeat its 5 minute timeout might make it more useful, but it's always going to need attention.
With that in mind, it's not very effective in the hottest weather. It needs to be expanded to 3 transducers.
Well, it needs a tall tank so the pump's side flow doesn't splash everywhere. Some fine tuning is required to get just enough pressure for a certain voltage without too much side flow. Once tuned, the PWM value could be hard coded. An ESC which doesn't constantly beep is required.
The hose fitting for the stock reservoir had the hose stop outside the reservoir, so the water went sideways instead of in the reservoir. It needs to go all the way into the reservoir to keep water from going sideways.
The stock reservoir was no longer water tight after drilling out the hose attachment. The original reservoir manetaned a vacuum which kept water in.
Without a water level sensor, the pump has to be manually toggled. Sensing water level would require a pretty complicated sensor. The stock tank is too small for any conventional sensor to fit. A conventional sensor would displace all the water. The leading theory is to have a custom ultrasonic sensor measure the resonant frequency of the tank.
It is believed the reservoir is as small as it is because the MEMS transducer leaks if any more pressure is applied. You couldn't attach a bigger tank & call it a day. A bigger tank could gravity feed into a smaller tank.
The MEMS atomizer requires 2 tanks, 2 circuit boards, 2 voltages, lots of wiring to the pump & the atomizer, a sensor to manage the water level. The atomizer & all the plumbing take a lot of space & have a lot of problems, which got the lion kingdom thinking of alternatives. The leading alternative is an automotive fuel pump
to atomize the water. It would require only 1 water tank & 1 pump. A test with a .2mm printer nozzle showed the printer nozzle with home made pump just squirted. It may require a lot more pressure to make a mist. That's why the safest bet is an automotive fuel injector with automotive fuel pump. They're just expensive.
The cheap pumps on the internet have sketchy reliability & are not self priming. They need animal power to get started, which makes topping off a tank a pain.
The home made pumps are not waterproof enough to last very long. Any submerged bearings or brushes would die quickly & contaminate the fluid with oil. All motors end up rusting & dying, including the commercial pumps.
What lions needed was a submersible pump which would last a long time in pulsed mode.
The lion kingdom went all the way to designing a simple reciprocating thing with a custom check valve & a solenoid driving a plunger.
The idea was the plunger would have enough drag to develop pressure without a seal. This was a failure. The valve couldn't keep the water out & a plunger without any seal couldn't develop any pressure. It might be more practical if the plunger was in a rail gun which accelerated it to high velocity & the valve had a spring loaded diaphragm.
The internet is all over the place regarding lifespan of submerged motors & the lion kingdom has a large inventory of small brushless outrunners, so the decision was made to try submerging one & see what happens.
It actually pumped some water through the tube, while burning .5A 6V. The seal around the motor was lousy. As an outrunner, it needed a gap around the motor which water was more inclined to flow through than the tube. An inrunner could block flow around the motor, but they're a lot scarcer & more expensive.
The water picked up a lot of oil from the motor. It was surprising just how easy it was to make a pump from a brushless motor.
The battery life was under 1 hour. Step 1 was eliminating the battery.
The inside was just a 200mAh battery & bog simple board, Sadly, the 5 minute timer was burned in the chip with no RC circuit anywhere. An outboard microcontroller could drop kick it every 5 minutes. It frequently stutters when water drops build up around the transducer & cover it, so a 5 minute drop kick wouldn't be noticeable.
The only functional parts are the board & a reservoir.
The transformer makes 120V p-p on 1 pin if the input voltage is 5V. The other pin is connected to B+. The output voltage drops to 110V p-p if the input voltage is 4.2V. The lion kingdom wanted to reduce the chance of burning out when it runs out of water so tried to drop the input voltage with a diode.
USB power could use a bit of capacitance to keep it from browning out. The next problem is expanding the reservoir. The easiest solution is seen as drilling out the top & fitting 2 pipes. 1 pipe allows water to be pumped in from a water bottle. A 2nd pipe lets air escape. The tank needs a water level sensor. It's expensive & hard to pump water. The 1st task is finding out how long the transducer lasts.
lion mclionhead
100mm Macro
