Arduino 120v AC Fan Control


I’m here seeking help for my project. I have a fan motor of which I have attached the wiring diagram to this forum post.

My project is to replace the controller on my humidifier with the arduino so I can program it and make it a smart humidifier. The only thing that has stumped me is how my current humidifier controller is able to control the fan speed of this motor. Coming out of the motor are three wires, a blue one, a white one, and a black one. There are 9 speed settings on the humidifier controller and I would like to be able to duplicate that with the arduino. I’m not sure what hardware I need to make that possible. Could anyone assist me in figuring out what I need?


The best help comes from your own work and understanding so the first step is some reverse engineering. Examine the 9 position switch, how many wires? Where do they go? Follow the motor wires. Where do the go? What’s on the control board?

If you want further help, photographs at a minimum would be required. A schematic from the owners manual is a huge help. If you don’t have one, do some online online research.

And be aware that most AC mains motors are either not speed-controllable, or have limited
speed control capabilities - getting it wrong can lead to excess current and overheating, so
you need to properly reverse-engineer this unit.