We just learned about the Servo, that has sensors to tell it when to start or stop.
One part of a servo is the Encoder.
An encoder is like a map that the servo uses, so when the machine moves it knows where it is and when to stop.
Encoders have markings on them that a sensor can see to tell the machine that it is moving.
A rotary encoder is a type of encoder for a machine that spins.
It has lines on it to help the machine figure out how far it spins around.
If a machine spins to the right, the sensor might see 10 black lines go by.
The machine would then know that if it wanted to go back to where it started, it could spin the other way until it counted 10 black lines go by.
(from: wikipedia - rotary encoder)
Kid Facts - Blast from the past: R-7 Rockets
