Rotary Encoders are a type of sensor typically used to measure the rotation speed of a shaft or motor. When coupled to a drive shaft or wheel, these can be used to determine distance traveled, correct differences in motor speeds, and even help determine if your robot is moving or stuck!
Encoder Disc$0.50Light Packet
Opto-Interrupter with Mounting Tabs$1.95Light Packet
Wheel Encoder Sensor$9.95Light Packet