RASPBERRY PI | SERVO CONTROL

In this project, students will learn how to control a servo motor using a Raspberry Pi. They will understand:

• How servos work and their applications.
• How to wire a servo to a Raspberry Pi using GPIO pins.
• How to write Python code to control the servo’s position.

Servo motors are commonly used in robotics, automation, and precision control applications such as robotic arms, RC vehicles, and robotic joints. This project provides a foundation for using servos in larger automation projects.

SECTION 1 | MATERIAL NEEDED

To complete this project, you will need:

• Raspberry Pi (any model with GPIO pins, e.g., Raspberry Pi 3, 4, or Zero W)
• Micro USB Power Supply (for powering the Raspberry Pi)
• Servo Motor (SG90 or MG996R recommended)
• Breadboard (optional but useful for stable connections)
• Jumper Wires (Male-to-Female for easy connections)
• Resistor (Optional, 330Ω-1kΩ) (for signal stabilization if needed)

SECTION 2| THE PRINCIPLES

How Servo Motors WorkServo motors are closed-loop control devices, meaning they move to a specified angle based on a control signal. They receive PWM (Pulse Width Modulation) signals, where:

• A 0.4 ms pulse moves the servo to the left position.
• A 2.5 ms pulse moves the servo to the right position.
• A middle position is calculated as the average of the two.

The PWM frequency used for servos is typically 50 Hz, meaning each cycle is 20ms long.

SECTION 3 | THE CONNECTIONS

Connect the servo motor to the Raspberry Pi’s GPIO pins as follows:

Servo Wire Connection

• Red (VCC) 5V (Physical Pin 2 or 4)
• Brown/Black (GND) GND (Physical Pin 6)
• Yellow/Orange (Signal) GPIO 13 (Physical Pin 33)

SECTION 3 | THE CODE

SECTION 2 | TROUBLE SHOOTING

Servo Not Moving

• Check Wiring: Ensure the signal wire is connected to GPIO 13, VCC to 5V, and GND to GND.
• Power Issue: Some servos require more current than the Raspberry Pi’s 5V pin can provide. Try using an external power source with a common ground.
• Incorrect Pin Numbering: Ensure GPIO.setmode(GPIO.BOARD) is used for physical pin numbering.

2. Servo Moves Erratically

• Check Power Supply: If the servo jitters, it may not be getting stable power.
• Reduce Delay Time: Use time.sleep(0.01) instead of time.sleep(0.5) for smoother motion.

3. Python Error: "ModuleNotFoundError: No module named ‘RPi’"

Install the GPIO library using:

• sudo apt update
• sudo apt install python3-rpi.gpio

4. Servo Moves Only Slightly
Adjust Pulse Width: Some servos may require a slightly different pulse width range (e.g., 0.5 ms to 2.4 ms instead of 0.4 ms to 2.5 ms).

Next Steps

• Modify the code to move the servo in response to a button press.
• Use multiple servos for robotic applications.
• Integrate the servo into a robotic arm project.