Waveshare Photo Interrupter Sensor, Speed Measuring

A photo interrupter works by shining light across a small gap and watching for interruptions as something passes through - typically a slotted disc attached to a rotating shaft, where each slot passing through generates a pulse that can be counted to calculate rotational speed. This sensor is built specifically for that speed-measuring role, giving a robotics or motor-control project a straightforward way to read wheel speed, motor RPM, or any other rotational rate without needing a more complex rotary encoder when a simple pulse count is all the application actually requires.