fanctl

Schematic

This project was meant to demonstrate closed loop PID control of a 3-pin PC fan. While the resulting board works, I learned that the tachometer pin on the fan is connected to a hall effect sensor, powered by +12V. This means that you cannot sense and control the fan's speed at the same time. I came to the conclusion that you should spend a few more dollars on a 4-pin fan that has an onboard MOSFET and a separate signal for PWM.

I'm providing the the code and board files here as they may still be interesting or useful as a reference or teaching tool.