ServoBlockWhat is a Servo?

A Servo is an Electro-Mechanical Positioning System and is the heart of Automation and Robotics.  The job of a Servo is to position some mechanical device or arm via a motor to a position that corresponds to an input signal.  This Position Signal to the Servo Input can be digital or analogue and represents the position of some mechanical device.   Let’s call this the “Want-Position” signal.

Rc Servos use a pulse of varying width for the Want-Position.  The Servo System also has to know the Present Position of this mechanical device.  Let’s call this the “IsNowPosition” signal.  This signal can be generated in many ways.  RC Servos use a variable resistor (Potentiometer) that is in some fashion attached to the mechanical device and is known as “Feedback Signal”.  The resistance changes as the device changes position.  A Micro-controller reads both of these Signals and compares them in order to decide which way the Motor has to turn to reach that position.  It then switches the appropriate Power-Transistors to turn the Motor on to turn in the right direction.  When the “WantPosition” signal and the “IsNowPosition” signal are equal in value the motor is instructed to stop.  Whenever the “WantPosition” signal is different from the “IsNowPosition” signal, the controller will turn on the motor in the appropriate direction until both signals reach equilibrium.