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: Controlling robotic arms, grippers, and joints.
• Remote-controlled vehicles: Steering systems and throttle control.
• Automation: Conveyor belt positioning and sorting mechanisms.
• Model building: Aircraft flaps, rudders, and other moving parts.
• Camera gimbals: Stabilizing and positioning cameras.

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 for standard servos)
• Operating Current: 100mA to 1A (depending on 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)

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 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 with a frequency of 50Hz. 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 your circuit.
• 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.
• Mechanical Stops: Avoid forcing the servo beyond its physical limits to prevent damage to the gears.

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 to control the servo

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: Excessive load or continuous operation at high torque.
   • Solution: Reduce the load or allow the servo to rest periodically.

4. Servo Stuck at One Position

   • Cause: Damaged gears or motor.
   • Solution: Inspect the servo for physical damage and replace it if necessary.

Q: Can I use a servo with a 3.3V microcontroller?
A: Yes, but you may need a level shifter for the PWM signal, and the servo must still be powered with 4.8V to 6V.

Q: How do I control a continuous rotation servo?
A: For continuous rotation servos, the PWM signal controls speed and direction rather than position. A 1.5ms pulse stops the servo, while shorter or longer pulses control rotation direction and speed.

Q: Can I connect multiple servos to one Arduino?
A: Yes, but ensure the power supply can handle the combined current draw of all servos. Use external power if necessary.

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