Iot-protocolsHow-ToBeginner · 3 min read

How to Use PIR Sensor with Raspberry Pi: Simple Guide

To use a PIR sensor with a Raspberry Pi, connect its output pin to a GPIO pin on the Pi and power it with 5V and ground. Then, write a Python script using the RPi.GPIO library to read the sensor's digital signal and detect motion.

📐

Syntax

Here is the basic syntax to read a PIR sensor using Python on Raspberry Pi:

GPIO.setmode(GPIO.BCM): Sets the pin numbering system.
GPIO.setup(pin, GPIO.IN): Sets the PIR sensor pin as input.
GPIO.input(pin): Reads the sensor state (0 or 1).

python

import RPi.GPIO as GPIO
import time

GPIO.setmode(GPIO.BCM)  # Use Broadcom pin numbering
pir_pin = 4            # Connect PIR output to GPIO4
GPIO.setup(pir_pin, GPIO.IN)  # Set pin as input

try:
    while True:
        if GPIO.input(pir_pin):
            print("Motion Detected!")
        else:
            print("No Motion")
        time.sleep(1)
except KeyboardInterrupt:
    GPIO.cleanup()

💻

Example

This example shows how to detect motion with a PIR sensor connected to GPIO4 on the Raspberry Pi. It prints "Motion Detected!" when movement is sensed and "No Motion" otherwise.

python

import RPi.GPIO as GPIO
import time

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

print("PIR Sensor Test (CTRL+C to exit)")
try:
    while True:
        if GPIO.input(pir_pin):
            print("Motion Detected!")
        else:
            print("No Motion")
        time.sleep(1)
except KeyboardInterrupt:
    print("Exiting program")
    GPIO.cleanup()

Output

PIR Sensor Test (CTRL+C to exit) No Motion No Motion Motion Detected! Motion Detected! No Motion ...

⚠️

Common Pitfalls

Incorrect wiring: Make sure the PIR sensor's output pin connects to a GPIO input pin, and power pins connect to 5V and ground correctly.
Wrong GPIO numbering: Use GPIO.BCM mode if you refer to GPIO numbers, not physical pin numbers.
No pull-up/down resistor: PIR sensors usually have built-in resistors, but if unstable readings occur, check wiring.
Not cleaning up GPIO: Always call GPIO.cleanup() to reset pins after your program ends.

python

import RPi.GPIO as GPIO

# Wrong way: Using physical pin numbering but setting BCM mode
GPIO.setmode(GPIO.BCM)
GPIO.setup(7, GPIO.IN)  # Pin 7 is physical pin, not BCM GPIO7

# Right way:
GPIO.setmode(GPIO.BOARD)  # Use physical pin numbering
GPIO.setup(7, GPIO.IN)    # Now pin 7 means physical pin 7

📊

Quick Reference

Summary tips for using PIR sensor with Raspberry Pi:

Connect PIR output to a GPIO input pin (e.g., GPIO4).
Power PIR sensor with 5V and ground pins.
Use GPIO.setmode(GPIO.BCM) for GPIO numbering.
Read sensor state with GPIO.input(pin).
Use try-except to handle exit and cleanup GPIO.

✅

Key Takeaways

Connect PIR sensor output to a Raspberry Pi GPIO input pin and power it properly.

Use Python with RPi.GPIO library to read the sensor's digital signal for motion detection.

Set GPIO mode to BCM to use GPIO pin numbers correctly.

Always clean up GPIO pins with GPIO.cleanup() after your program ends.

Check wiring and pin numbering carefully to avoid common mistakes.