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Insight - How Servo Motor works

Written By: 

Ashok Sharma


Servo Motors are DC Motors (check out how DC motor works) with a servo mechanism to provide a precise angular motion. Pulse width modulation (PWM) technique is used to set the angle of rotation. Generally RC servo motors have a rotation limit of 900 to 1800 but servos with high rotation angles are also available.
DC Servo Motor
Fig. 1: Image Showing Servo Motor with a Rotation Limit of 180 Degrees
A Servo motor with a rotation limit of 1800 is shown in the image.
Servo Motor Wiring
Fig. 2: Three Inputs of Servo Motor
A servo needs three inputs to operate - one for positive voltage, second for ground and third one for PWM.

Feedback Circuitry

Servo Motor Feedback Circuit
Fig. 3: Circuit for Control and Feedback Providing Components
The circuit shown in the above image consists of the necessary control and feedback providing components.
Servo Motor ARM
Fig. 4: Image showing Servo Horn, also Known as Servo Arm
A servo horn or also known as servo arm which rotates with the motor spindle.

Gear Arrangement

Servo Motor Gear Assembly
Fig. 5: Image showing Arrangement of Gears
Gears arrangement plays an important role to provide necessary high torque and to provide feedback.
Servo Motor Gears
Fig. 6: Image showing Various Gears used in Servo Meter
The above image shows various gears used in a servo motor.

Motor & Potentiometer

Motor and Potentiometer in Servo motor
Fig. 7: DC Motor and Potentiometer used to Provide Feedback to Electronic Circuitry
The above image shows the DC motor and the potentiometer which is used to provide feedback to the electronic circuitry. It is connected with the DC motor with the help of gear assembly. As soon as the motor starts rotating the potentiometer also starts rotating and the output of potentiometer i.e. voltage across the middle terminal changes which acts as the feedback signal to indicate the degree of rotation of the motor.
For detailed working see the Servo motor control in the article section.


Hi, I want to ask how do I determine a pulse for a servo motor. I have a C36R servo motor and determine th pulse so that I can determine the position

you should use micro-controller and shift register to give position and pulse


hi ,i want to know how to program servo motor


how can i determine the pwm technique on CRO.???


hi plz send me the code for GSM based home appliance security system mini project as early as possible...