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 industrial machinery due to their ability to provide accurate and repeatable motion.

• Robotics: For controlling robotic arms, grippers, and joints.
• Remote-controlled vehicles: Steering mechanisms and throttle control.
• Automation: Conveyor systems and precise positioning tasks.
• Hobby projects: Model airplanes, boats, and cars.
• Camera gimbals: Stabilization and precise 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: 0° to 180° (standard), 360° for continuous rotation servos
• Control Signal: Pulse Width Modulation (PWM)
  • Pulse width: 1ms (0°), 1.5ms (90°), 2ms (180°)
  • Frequency: 50Hz (20ms period)

The servo typically has three wires for connection:

1. Power the Servo: Connect the VCC pin to a 5V or 6V power source and the GND pin to the ground of the circuit.
2. Control Signal: Connect the Signal pin to a PWM-capable pin of a microcontroller (e.g., Arduino).
3. PWM Signal: Generate a PWM signal with a frequency of 50Hz and adjust the pulse width to control the servo's position:
   • 1ms pulse: 0° position
   • 1.5ms pulse: 90° position
   • 2ms pulse: 180° position

• Power Supply: Use a separate power supply for the servo if it draws significant current, as this can prevent voltage drops in the microcontroller.
• Avoid Overloading: Do not exceed the torque rating of the servo to avoid damage.
• Signal Stability: Ensure the PWM signal is stable and within the specified frequency range.
• Continuous Rotation Servos: For continuous rotation servos, the pulse width controls speed and direction rather than position.

Below is an example of how to control a servo using an Arduino UNO:

#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 running it continuously at high torque.
   • Solution: Reduce the load or use a servo with a higher torque rating.

4. Limited Range of Motion

   • Cause: Mechanical obstruction or incorrect PWM signal.
   • Solution: Check for physical obstructions and verify the pulse width range.

• Q: Can I power the servo directly from the Arduino?
  A: While possible for small servos, it is recommended to use an external power supply to avoid overloading the Arduino.

• Q: How do I control a continuous rotation servo?
  A: For continuous rotation servos, use the myServo.write() function with values around 90 for stop, less than 90 for one direction, and greater than 90 for the opposite direction.

• 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.

This documentation provides a comprehensive guide to understanding and using a servo in various applications.