This project implements a 4-channel PWM controller for PWM-controlled (four-pin) PC fans.

I.e. the built controller can control up to four such PC fans.

Hardware used

It uses an Atmel ATMega328P 8-bit micro-controller to read a linear potentiometer and generates four shifted PWM output signals to drive up to four PWM-controlled PC fans.

Schematics

The schematics directory contains a KiCad Project with both the schematics and a circuit board design meant to be placed by hand on a stripboard.

The potentiometer used to control the fan speed is read using a simple voltage divider and the A/D converter built into the mircocontroller. Whilst the accuracy is not the best, it is good enough for the purpose of controlling fans. The dead ends on both ends of the potentiometer range allow for reliably hitting the 100% and 0% load settings.

Circuit Board

The supplied circuit board design is not meant to be used to produce a printed circuit board (PCB), but rather be a guide to place the components on a cut stripboard with a 2.54mm grid and connected copper lines on the back. The copper lines on the top are meant to be placed using wire bridges. The layout can be simplified greatly for a “proper” PCB design.

3D-Render of the circuit board: