Have you ever wanted to combine the world of Micro Controllers with a multi-speed fan motor? Maybe it’s just me! After figuring out how the old exhaust fan from the microwave oven has to be wired, I decided it would be great if I could introduce a bit of automation instead of simply relying on a physical switch to turn on and off the motor.
I had started probing this fan with the intention of using it as an Exhaust fan for the Laser Cutter / Engraver I ordered last week. My vision is to basically have Up and Down buttons which will cycle the fan through Off / Low / Medium-Low / Medium-High / High. It will be really nice to have a variable fan instead of a fixed speed because working with paper or low smoke items will not require as much ventilation and would allow me to save my ears a little bit and hopefully not interrupt my wife’s sleep in the room next door. I would also like to entertain the option of adding another button to enable a “purge setting” although this could simply be one step above High. Essentially after using the laser I may want to purge the cabinet of extra fumes before opening the lid. To do this it would be nice to simply press a button and the fan turns to high speed for 45 seconds and then shuts itself off.
I will warn everyone that it is dangerous working with main’s level voltage and there is always risk involved and not limited to just burning your house down or death.
After a late sleepless night, I managed to bang out a working prototype. For the prototyping process, I simply used an Arduino Mega which will be replaced with a Standalone Arduino and wrote the code to simply cycle through each speed after 5 seconds.
The wiring included using four relays from my parts bin (one for each speed setting). The relays are rated at 15 amps at 120 VAC so they should be plenty big enough given my previously measured current loads. The coils only pull 20 miliamps each so I can simply run them straight off of the Arduino pins with no need for another transistor. While I have no safety mechanism built into the hardware to prevent two legs of the motor from both being activated at once, I don’t anticipate any heavy duty coding on the micro controller so things shouldn’t get to confusing that I would accidentally enable more than one relay.
That said, my mind spinning an idea of expanding this into an automated solution enabling the water pump and air assist circuits later on!
Below is a quick video showing the fan run through the various speeds and apparently my son doing a few experiments to see how much force it would apply to a package of BB Gun pellets.