Insight - How Servo Motor works

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.

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.

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

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.

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

Fig. 5: Image showing Arrangement of Gears

Gears arrangement plays an important role to provide necessary high torque and to provide feedback.

Fig. 6: Image showing Various Gears used in Servo Meter

The above image shows various gears used in a servo motor.

Motor & Potentiometer

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.