Servo Motors

1. Definition

1.1 Servo Motor

A servo motor is a DC motor with gears, a sensor, and a small controller inside that allows it to move to and hold a specific angle.

Common hobby servos rotate 0° to 180°, while continuous rotation servos act more like geared DC motors (they keep spinning).

Servo Motor example

Servo Symbol

Servo symbol

1.2 Types of Servos

  • Positional Rotation: Limited to a fixed range (e.g., 0° to 180°).
  • Continuous Rotation: Spins freely in either direction (speed controlled by PWM).
  • Linear Servos: Move back and forth in a straight line instead of rotating.

2. Features

  • Controlled by a PWM (Pulse Width Modulation) signal.
  • Built-in gearing for higher torque.
  • Internal feedback system for accurate positioning.
  • Typical operating voltage: 4.8V to 6V (some up to 7.4V for high-performance models).
  • Torque (strength) & speed vary by model check datasheets before use.

4. How to Use

Safety Note

Never force the servo horn by hand, you can strip the internal gears.

4.1 Wiring

  • Brown or Black: Ground (GND)
  • Red: Power (Vcc)
  • Orange or Yellow: PWM control signal (connect to Arduino PWM pin, e.g., pin 9)

Servo pinout

4.2 Controlling

  • Send a short pulse every 20ms to set the angle:
    • 1ms pulse → 0° (full left)
    • 1.5ms pulse → 90° (center)
    • 2ms pulse → 180° (full right)
  • Arduino makes this easy using the built-in Servo library:

Video Explanation

video coming soon