Low speed motor Encoder with LED and LDR

Simple encoder with Arduino, LED and LDR

This model illustrates motor encoder using an LED and LDR.
A black disk with a single hole (where light passes through) is attached to the motor shaft. Each time the motor completes a revolution, the LED light passes through the hole and LDR receives it, which then alter the resistance of the LDR and hence the signal reading at the digital input port.