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Smart Air Compressor Power


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A few weeks ago, I installed shop air in my garage.  I was pretty proud when it held 150psi all night.  But of course I did not quite tighten a connection and at 2 AM (or so my daughter tells me) there was a loud bang followed by a steady "compressor" noise.  I did not notice until the next morning when I wondered why there was a noise from the garage.  That compressor was pretty hot for running 6 hours straight.

Of course this could be stopped by turning the compressor off each night.  But, I write embedded software for a living and lately I have been deep into IoT projects.  Naturally, this was an ideal chance to do something about my dumb compressor.


First, I needed a way to switch the compressor on-off remotely.  These Sonoff switches are almost perfect.


On the plus side, they have an ESP8266 inside so I can run TASOMOTA which is a generic Home Automation / IoT firmware for all things 8266.  On the down side, they only are good for 10A.  So I added a 120VAC 2 pole relay good for 30A.  The compressor has a 16.6A motor draw so some overkill seems appropriate.

I refreshed the Sonoff Basic with Tasmota and installed everything inside a metal electrical box.


And when I visited the web page:


I can turn the compressor on/off from my phone.  Fantastic!

As long as I had everything opened up, I went ahead and added 2 pressure sensors.


Left and right of the primary pressure regulator.  The left side sensor goes to the compressor and lets me know what it is doing.  I am now tempted to remove the mechanical hysteretic controller on the compressor and simply use the Sonoff switch and some electronic pressure sensing to do the same thing.  We shall see.

Everything is now in place to ensure the compressor can be automatically turned off, or have a maximum run limit.  The only thing left is software!

Good Luck.

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I had a similar choice on the CO2 valve for my fishtank, but if my sw had any glitch the tank would be carbonated like soda and everything would die from the ph drop, so I decided to leave the mechanical regulator in the line for a backup if the electronics fail for some reason. You never know what happens when the power goes out or a battery dies at the wrong time...

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I am leaning towards adding a current transformer to the smart switch.  Then I have positive feedback that the regulator is also commanding the motor to be on and I can more positively put a time limit on the motor run.

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