SENSORS/ACTUATORS

Raspberry Pi - Motion Sensor - Servo Motor

This tutorial instructs you how to use Raspberry Pi and motion sensor to control servo motor. In detail:

If a motion is detected, Raspberry Pi rotates the servo motor to 90 degrees
If no motion is detected, Raspberry Pi rotates the servo motor back to 0 degrees.

This can be applied in an automation process that triggers actions upon detecting human presence.

Hardware Preparation

1	×	Raspberry Pi 4 Model B
1	×	HC-SR501 Motion Sensor
1	×	Servo Motor
1	×	Jumper Wires
1	×	(Optional) Screw Terminal Adapter for Raspberry Pi

Or you can buy the following sensor kits:

1	×	DIYables Sensor Kit (30 sensors/displays)
1	×	DIYables Sensor Kit (18 sensors/displays)

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Overview of Servo Motor and Motion Sensor

If you are unfamiliar with servo motors and motion sensors (including pinouts, how they work, and how to program them), the following tutorials can help:

Wiring Diagram

This image is created using Fritzing. Click to enlarge image

Please note that the wiring diagram shown above is only suitable for a servo motor with low torque. In case the motor vibrates instead of rotating, an external power source must be utilized to provide more power for the servo motor. The below demonstrates the wiring diagram with an external power source for servo motor.

TO BE ADD IMAGE

Please do not forget to connect GND of the external power to GND of Arduino Raspberry Pi.

Initial Setting


Time Delay Adjuster	Screw it in anti-clockwise direction fully.
Detection Range Adjuster	Screw it in clockwise direction fully.
Repeat Trigger Selector	Put jumper as shown on the image.

Raspberry Pi Code - Motion Sensor Controls Servo Motor

Detailed Instructions

Make sure you have Raspbian or any other Raspberry Pi compatible operating system installed on your Pi.
Make sure your Raspberry Pi is connected to the same local network as your PC.
Make sure your Raspberry Pi is connected to the internet if you need to install some libraries.
If this is the first time you use Raspberry Pi, See how to set up the Raspberry Pi
Connect your PC to the Raspberry Pi via SSH using the built-in SSH client on Linux and macOS or PuTTY on Windows. See to how connect your PC to Raspberry Pi via SSH.
Make sure you have the RPi.GPIO library installed. If not, install it using the following command:

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

Create a Python script file motion_sensor_servo.py and add the following code:

# This Raspberry Pi code was developed by newbiely.com # This Raspberry Pi code is made available for public use without any restriction # For comprehensive instructions and wiring diagrams, please visit: # https://newbiely.com/tutorials/raspberry-pi/raspberry-pi-motion-sensor-servo-motor import RPi.GPIO as GPIO import time # Constants won't change MOTION_SENSOR_PIN = 14 # Raspberry Pi GPIO pin connected to the OUTPUT pin of the motion sensor SERVO_PIN = 12 # Raspberry Pi GPIO pin connected to the servo motor # Variables will change angle = 0 # The current angle of the servo motor prev_motion_state = None # The previous state of the motion sensor motion_state = None # The current state of the motion sensor # Setup GPIO GPIO.setmode(GPIO.BCM) GPIO.setup(MOTION_SENSOR_PIN, GPIO.IN) GPIO.setup(SERVO_PIN, GPIO.OUT) # Create PWM instance for servo servo_pwm = GPIO.PWM(SERVO_PIN, 50) # 50 Hz frequency # Initialize servo position servo_pwm.start(0) try: while True: prev_motion_state = motion_state # Save the last state motion_state = GPIO.input(MOTION_SENSOR_PIN) # Read new state if motion_state == GPIO.LOW and prev_motion_state == GPIO.HIGH: print("Motion detected!") servo_pwm.ChangeDutyCycle(7.5) # Adjust duty cycle for 90 degrees elif motion_state == GPIO.HIGH and prev_motion_state == GPIO.LOW: print("Motion stopped!") servo_pwm.ChangeDutyCycle(2.5) # Adjust duty cycle for 0 degrees time.sleep(0.1) # Add a small delay to avoid rapid sensor readings except KeyboardInterrupt: servo_pwm.stop() GPIO.cleanup()

Save the file and run the Python script by executing the following command in the terminal:

python3 motion_sensor_servo.py

Wave your hand in front of the sensor.
Check out the change in the angle of the servo motor.

The script runs in an infinite loop continuously until you press Ctrl + C in the terminal.

Video Tutorial

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