Guide on How a Servo Motor Works

Inside the servo motor, there is a built-in 'DC' (direct current) motor with gearing and feedback control loop circuitry. This gearing enables speed reduction and high torque production. The control loop circuitry is responsible for its high precision control. This reduces the need for additional motor driver circuit. Servos or servo motors in this project rotate from approximately 90 to 180 degrees range. Note that servos can be modified to rotate continuously (360 degrees).

Wiring of the servo is simple; red wire is for 'DC' +5V, black wire connects to 'GND' (ground) and white wire for signal (where PWM Circuit is sent to the motor). The white wire is responsible for controlling degree of rotations.

Voltages from 4.8V to 6.0V can be used to power a servo. Higher voltage rating (6.0V) produces higher torque. But for safety conservation, a regulated 'DC' voltage of 5V is used. This way, servo motors would not exceed its maximum voltage limit.

The servo motors are usually powered by batteries. This power source is then regulated to 5V (using voltage regulator). Amount of voltage depends on applications needed. 5V voltage is enough to drive torque to perform useful motions. Commonly, servo motors are powered by smaller batteries like Nickel Cadmium ('NiCd') or Nickel-Metal Hydride ('NiMh') or even the latest; Lithium Polymer ('LiPo').

External power supply delivers power the motors. Power supply to micro controller circuit board should be separate, and powered by computer universal serial bus 'USB' (Universal Serial Bus) connection. Both power supplies ground connections must be in common to each other, for the servo motors to function properly.

A pulse of 1.5milisecond (ms) will always set servo to its neutral position (90 degrees). A minimum pulse of 1ms sets it to turn 90 degrees left. A maximum pulse of 2ms will bring it to the 180 degrees position. These pulse width or 'PWM' (pulse width modulation) can vary, depending on programming of micro controller. For example, servo will turn to approximately 45 degrees if given a 'PWM' of 1.25ms.

Alfred writes on self-improvement and provides useful tips about its relevant topics. You can also find him where he has a website which helps people find Induction Heater, Custom Electronics, Electronic Circuits at www.rmcybernetics.com