Build your own Rotary Encoder

Here’s how to turn a small stepper motor into an encoder. After all, a stepper motor has permanent magnets inducing voltages in the rotor coils. Without going into too much detail, a stepper motor requires two signals with a phase difference of 90 degrees. The voltages generated per coil can then be said to represent a ‘Gray code’, that is, two voltages 90 degrees out of phase.