MotionSensor (PIR) in Raspberry Pi - Mini Project: Build & Apply

MotionSensor (PIR) with Raspberry Pi

📖 Scenario: You have a Raspberry Pi connected to a PIR motion sensor. The sensor detects movement in a room and sends a signal to the Pi. You want to write a simple program to read the sensor's signal and print a message when motion is detected.

🎯 Goal: Build a Python program that reads input from a PIR motion sensor connected to the Raspberry Pi's GPIO pin and prints "Motion detected!" when movement is sensed.

📋 What You'll Learn

Use the RPi.GPIO library to interact with GPIO pins.

Set up the GPIO pin connected to the PIR sensor as input.

Detect when the PIR sensor output goes HIGH (motion detected).

Print "Motion detected!" each time motion is detected.

💡 Why This Matters

🌍 Real World

Motion sensors are used in home security systems, automatic lighting, and energy-saving applications to detect presence and movement.

💼 Career

Understanding how to read sensor input and control GPIO pins is essential for embedded systems, IoT development, and hardware interfacing jobs.

1

Set up GPIO and PIR sensor pin

Import the RPi.GPIO library as GPIO and set the GPIO mode to GPIO.BCM. Create a variable called pir_pin and set it to 4, which is the GPIO pin number connected to the PIR sensor.

Raspberry Pi

# Import RPi.GPIO and set GPIO mode
# Your code here

Need a hint?

Use import RPi.GPIO as GPIO to import the library. Use GPIO.setmode(GPIO.BCM) to set pin numbering. Assign 4 to pir_pin.

2

Configure PIR pin as input

Use GPIO.setup to set the pir_pin as an input pin.

Raspberry Pi

import RPi.GPIO as GPIO
GPIO.setmode(GPIO.BCM)
pir_pin = 4
# Set pir_pin as input
# Your code here

Need a hint?

Use GPIO.setup(pir_pin, GPIO.IN) to configure the pin as input.

3

Detect motion with a loop

Write a while True loop that reads the PIR sensor state using GPIO.input(pir_pin). If the input is GPIO.HIGH, print "Motion detected!".

Raspberry Pi

import RPi.GPIO as GPIO
GPIO.setmode(GPIO.BCM)
pir_pin = 4
GPIO.setup(pir_pin, GPIO.IN)

# Start infinite loop to detect motion
# Your code here

Need a hint?

Use while True: to create an endless loop. Inside, check if GPIO.input(pir_pin) equals GPIO.HIGH. If yes, print the message.

4

Clean up GPIO on exit and run program

Add a try-except block around the loop to catch KeyboardInterrupt. Inside except, call GPIO.cleanup() to reset GPIO pins. Run the program and observe the output when motion is detected.

Raspberry Pi

import RPi.GPIO as GPIO
GPIO.setmode(GPIO.BCM)
pir_pin = 4
GPIO.setup(pir_pin, GPIO.IN)

# Add try-except to handle keyboard interrupt and cleanup GPIO
# Your code here

Need a hint?

Use try: before the loop and except KeyboardInterrupt: after. Inside except, call GPIO.cleanup().