DIY optical rotary encoder for geared motors

One of the most important things in robotics is to accurately sense and control the rotation of a motor. One way to do this is to use stepper motors but they’re bulky, have very less torque and speed. Another is to buy a motor with quad encoders which work on the basis of hall effect, they give a very high resolution of about 10000-20000 counts/rotation but they’re very expensive. In this tutorial I’m going to show you how to build a very simple attachment to any geared motor to measure the angular rotation