![](https://cdn.hackaday.io/images/4703221626322836937.jpg)
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.
![](https://cdn.hackaday.io/images/4388061626322858198.jpg)
The water level sensor was well & truly corroded after just 1 day.
![](https://cdn.hackaday.io/images/819101626322894157.jpg)
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.
![](https://cdn.hackaday.io/images/5369411626383112501.jpg)
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.
![](https://cdn.hackaday.io/images/2620851626550262904.jpg)
![](https://cdn.hackaday.io/images/6753221626550263215.jpg)
![](https://cdn.hackaday.io/images/7616581626633559225.jpg)
https://www.amazon.com/Sprayer-Portable-Atomization-Extensions-Rechargeable/dp/B08HK6Q95R
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.
![](https://cdn.hackaday.io/images/7786011626633663287.jpg)
![](https://cdn.hackaday.io/images/7801531626633709001.jpg)
![](https://cdn.hackaday.io/images/3101601626633741484.jpg)
![](https://cdn.hackaday.io/images/9476711626633809705.jpg)
![](https://cdn.hackaday.io/images/559931626633845461.jpg)
Through hole soldering is still essential for an experimental design like this.
![](https://cdn.hackaday.io/images/5734801626634024606.jpg)
![](https://cdn.hackaday.io/images/1457441626634025672.jpg)
It worked, with all the misters being managed automatically.
![](https://cdn.hackaday.io/images/4005341626634068714.jpg)
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.
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