How to Use Servo: Examples, Pinouts, and Specs

A servo is a rotary actuator that allows for precise control of angular position, velocity, and acceleration. It consists of a motor coupled to a sensor for position feedback, along with a control circuit. Servos are widely used in robotics, automation, remote-controlled vehicles, and other applications requiring accurate movement and positioning.

• Robotics: For controlling robotic arms, grippers, and joints.
• Remote-controlled vehicles: Steering mechanisms and throttle control.
• Automation: Conveyor belts, camera gimbals, and industrial machinery.
• Hobby projects: Model airplanes, boats, and cars.
• DIY electronics: Projects requiring precise angular movement.

Below are the general technical specifications for a standard hobby servo. Note that specifications may vary depending on the specific model and manufacturer.

• Operating Voltage: 4.8V to 6V (typical range)
• Current Draw: 10mA to 100mA (idle), up to 1A (under load)
• Torque: 1.5 kg-cm to 20 kg-cm (varies by model)
• Rotation Range: Typically 0° to 180° (some models support 360° continuous rotation)
• Control Signal: Pulse Width Modulation (PWM)
  • Pulse width: 1ms (0°), 1.5ms (90°), 2ms (180°)
  • Frequency: 50Hz (standard)

Servos typically have three wires for connection. The pinout is as follows:

1. Power the Servo: Connect the VCC pin to a 5V power source and the GND pin to the ground of your circuit.
2. Control Signal: Connect the Signal pin to a PWM-capable pin on your microcontroller (e.g., Arduino).
3. PWM Signal: Generate a PWM signal to control the servo's position. The pulse width determines the angle:
   • 1ms pulse: 0° position
   • 1.5ms pulse: 90° position
   • 2ms pulse: 180° position

• Power Supply: Use a separate power source for the servo if it draws significant current, as it may cause voltage drops in your circuit.
• Avoid Overloading: Do not exceed the torque rating of the servo to prevent damage.
• Signal Stability: Ensure the PWM signal is stable and within the specified frequency range (50Hz for most servos).
• Mechanical Limits: Avoid forcing the servo beyond its physical rotation limits to prevent damage.

Below is an example of how to control a servo using an Arduino UNO and the Servo library.

#include <Servo.h> // Include the Servo library

Servo myServo; // Create a Servo object

void setup() {
  myServo.attach(9); // Attach the servo to pin 9 on the Arduino
}

void loop() {
  myServo.write(0); // Move the servo to 0 degrees
  delay(1000);      // Wait for 1 second

  myServo.write(90); // Move the servo to 90 degrees
  delay(1000);       // Wait for 1 second

  myServo.write(180); // Move the servo to 180 degrees
  delay(1000);        // Wait for 1 second
}

• The Servo library simplifies the process of generating PWM signals.
• The myServo.attach(9) function links the servo to pin 9.
• The myServo.write(angle) function sets the servo to a specific angle (0° to 180°).

1. Servo Not Moving

   • Cause: Incorrect wiring or insufficient power supply.
   • Solution: Double-check the connections and ensure the power supply meets the servo's requirements.

2. Jittery or Erratic Movement

   • Cause: Unstable PWM signal or electrical noise.
   • Solution: Use a decoupling capacitor near the servo's power pins and ensure the PWM signal is stable.

3. Overheating

   • Cause: Overloading the servo or continuous operation under high torque.
   • Solution: Reduce the load on the servo or allow it to rest periodically.

4. Limited Rotation

   • Cause: Using a standard servo instead of a continuous rotation model.
   • Solution: Verify the servo type and ensure it matches your application.

Q: Can I power the servo directly from the Arduino?
A: While possible for small servos, it is not recommended for larger servos due to high current draw. Use an external power source.

Q: How do I control a 360° continuous rotation servo?
A: Instead of setting angles, you control the speed and direction using the PWM signal. A 1.5ms pulse stops the servo, while shorter or longer pulses control the direction and speed.

Q: Can I connect multiple servos to a single Arduino?
A: Yes, but ensure the power supply can handle the combined current draw of all servos. Use separate PWM pins for each servo.

Q: What happens if I exceed the servo's torque rating?
A: Exceeding the torque rating can damage the servo's internal gears or motor. Always operate within the specified limits.