It explains how slot-type optocouplers work, how this module converts mechanical motion into clean digital pulses, how to calculate speed and RPM correctly, and how to interface it reliably with Arduino for motors, wheels, encoders, and rotating machinery. This tutorial is a comprehensive, practical guide to the Speed Sensor / Tacho Sensor (Slot-Type Optocoupler) (Leobot Product #245). Does anyone have any suggestions or idea? Thanks ypu for the help. Measure rotation speed (RPM) with Optocoupler and Encoder disk and Arduino - Quick and Easy! Beginner Protip 12 minutes 64,451 When building a robot car, it is important to control the speed of the rotation of the wheels. Slotted optocoupler speed modules, like these two models below: They work with optocoupler sensors—when something blocks them, they put out a high level.