An optocoupler speed sensor measures motor RPM by converting rotation into a stream of electrical pulses. Let's talk about two super common speed modules first: 1. They've got an LM393 comparator inside, and you can use 'em for motor speed detection. This tutorial is a comprehensive, practical guide to the Speed Sensor / Tacho Sensor (Slot-Type Optocoupler) (Leobot Product #245). 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. One of the easiest and most popular ways of measuring the speed is with Optocoupler, and Encoder Wheel. Most of the Smart Car kits come with Encoder Wheels included, and I already made Instructable on how to connect Optocoupler to Arduino. Now I will show you how you can use the Optocoupler to. Measure rotation speed (RPM) with Optocoupler and Encoder disk and Arduino - Quick and Easy! When building a robot car, it is important to control the speed of the rotation of the wheels. As long as a non-transparent object passes through the slot, it can trigger to output a low TTL level.