[Jesse Merritt] bought a manual speed controller for his router. It’s used in the CNC mill he build and he figured, why not add the ability for the computer to control the speed.
The speed controller is a $20 unit from Harbor Freight. It comes with an On/Off switch and knob which adjusts the power going to the router. [Jesse] pulled off the knob and milled a gear which takes its place. The second gear is attached to the horn of a hobby servo mounted on the side of the speed controller. The video after the break demonstrates an Arduino driving the servo based on a potentiometer input as well as commands from the CNC controller board he’s using.
Design files for the gears and the Arduino code which drives the servo is available from his Github repository.