I could've tried to single sweep the scope, turn the motor one revolution, and then physically try to count the peaks (not very efficient or elegant), but the scope had a pulse-count measurement. I ...

For their Hackaday Prize project, [besenyeim] is doing it differently: they’re using motors as coupled inductors, and it looks like this is a viable way to turn a motor into an encoder.

A rotary encoder is an electro-mechanical device for converting the angular position of a shaft or axle to a digital code. For many applications and equipment that need to track object location, ...

I needed a rotary encoder — I pulled a cheap one out of one of those “49 boards for Arduino” kits you see around. Not the finest encoder in the land, I’m sure, but it should do the job.

The encoders’ special properties are that they have a very compact design, excellent signal quality and therefore high interpolation rates, as well as excellent thermal position stability. The ...