We were using reflectance sensors. Either way there’s a trick to detecting which direction a rotary encoder is turning. We’ll explain that for you after the break.

The disc rotation creates a light-dark pattern through the clear and opaque disc segments. An absolute encoder has multiple detectors and a disc with multiple, unique tracks.

Absolute encoders contain multiple detectors and up to 20 tracks of segment patterns. For each encoder position, there is a different binary output -- shaft position is absolutely determined.

Rotary encoders are pretty interesting pieces of technology. They’re a solid way to accurately measure rotation including the direction. [David] recently wrote some software to handle these i… ...