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 precise motion control. Their ability to move to a specific angle and hold that position makes them ideal for tasks such as steering mechanisms, robotic arms, and pan-tilt camera systems.

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)
• Operating Current: 100mA to 1A (depending on load)
• Torque: 1.5 kg-cm to 20 kg-cm (varies by model)
• Speed: 0.1 to 0.2 seconds per 60° (at no load)
• Control Signal: Pulse Width Modulation (PWM)
• Angle Range: 0° to 180° (standard), some models support 360° continuous rotation
• Connector Type: 3-pin (Signal, VCC, GND)

The servo typically has a 3-pin connector with the following pinout:

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: Send a PWM signal to the servo to control its position. The pulse width determines the angle:
   • A pulse width of 1ms corresponds to 0°.
   • A pulse width of 1.5ms corresponds to 90° (center position).
   • A pulse width of 2ms corresponds to 180°.

• 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.
• PWM Frequency: Most servos operate at a PWM frequency of 50Hz (20ms period).
• Calibration: Some servos may require calibration to ensure accurate positioning.

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
}

Explanation:

• The Servo library simplifies controlling the servo.
• The attach() function links the servo to a specific pin.
• The write() function sets the servo 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. Servo Jittering:

   • Cause: Electrical noise or unstable power supply.
   • Solution: Use a capacitor across the power pins to stabilize the voltage.

3. Servo Overheating:

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

4. Servo Not Reaching Full Range:

   • Cause: Incorrect PWM signal or servo limitations.
   • Solution: Verify the PWM signal timing and check the servo's specifications.

• Q: Can I connect multiple servos to an Arduino?

  • A: Yes, but ensure the power supply can handle the combined current draw of all servos.

• Q: What happens if I send a PWM signal outside the 1ms to 2ms range?

  • A: The servo may behave unpredictably or attempt to move beyond its physical limits, potentially causing damage.

• Q: Can I use a servo for continuous rotation?

  • A: Yes, but you need a continuous rotation servo, which interprets PWM signals as speed and direction rather than position.

By following this documentation, you can effectively integrate and troubleshoot a servo in your projects.