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Lesson 12: PIR Motion Module (HC-SR501)

In this lesson, you’ll learn how to connect a PIR Motion Sensor to the Raspberry Pi Pico W. You’ll discover how to configure the sensor for motion detection and use basic MicroPython code to react to movement. By monitoring the PIR sensor, you’ll gain experience in managing digital inputs and creating a simple security measure or automation trigger.

Required Components

In this project, we need the following components.

It’s definitely convenient to buy a whole kit, here’s the link:

Name	ITEMS IN THIS KIT	LINK
Universal Maker Sensor Kit	94	Universal Maker Sensor Kit

You can also buy them separately from the links below.

Component Introduction	Purchase Link
Raspberry Pi Pico W	BUY
PIR Motion Module (HC-SR501)	-
Breadboard	BUY

Wiring

Code

from machine import Pin
import time

# Initialize PIR sensor connected to pin 16 as input
pir_sensor = Pin(16, Pin.IN)

while True:
    # Check the PIR sensor value
    if pir_sensor.value() == 0:
        print("Monitoring...")  # No motion detected
    else:
        print("Somebody here!")  # Motion detected

    time.sleep(0.1)  # Short delay of 0.1 seconds to reduce CPU usage

Code Analysis

Importing modules

The machine module is imported to use the Pin class for GPIO pin control. The time module is imported for creating delays in the loop.
```
from machine import Pin
import time
```
Initializing the PIR sensor

The PIR sensor is connected to GPIO pin 16 of the Raspberry Pi Pico W. It is set as an input device because it sends data to the microcontroller.
```
# Initialize PIR sensor connected to pin 16 as input
pir_sensor = Pin(16, Pin.IN)
```

Main loop

The while True loop makes the code run continuously. Inside this loop, the PIR sensor’s value is checked. If the value is 0, it means no motion is detected. Otherwise, motion is detected. A delay of 0.1 seconds is added to reduce CPU usage and prevent the code from running too fast.

while True:
    # Check the PIR sensor value
    if pir_sensor.value() == 0:
        print("Monitoring...")  # No motion detected
    else:
        print("Somebody here!")  # Motion detected

    time.sleep(0.1)  # Short delay of 0.1 seconds to reduce CPU usage