Introduction to Servos and Servomechanisms

Servos are motors that use feedback to control the motor's position. This type of control is called closed loop control. Servos use a special electromechanical device to provide this feedback. This electromechanical device can be a potentiometer or encoder. Encoders come in various shapes, sizes and resolutions. Encoders provide a pulse (usually caused by an LED and sensor) that determines the position of the shaft of the motor. When the controller counts to the commanded number of pulses, the motor is stopped, or put into reverse if the motor over ran the position. The motor and controller will constantly provide torque in the direction that is needed to keep the position and is always correcting. If a potentiometer is used, the motor shaft is connected to the potentiometer in some way (hobby servos connect the potentiometer with gears).