Pi and PIR example

In this example we connect a PIR module up to our Raspberry PI, this is quite a simple module to connect as it requires only 5v, Gnd and the output is PI friendly so does not require any level shifting.

A passive infrared sensor (PIR sensor) is an electronic sensor that measures infrared (IR) light radiating from objects in its field of view. They are most often used in PIR-based motion detectors.

Here is a typical PIR which can be commonly found on the internet and is used in many projects. This is known as the HC-SR501 PIR MOTION DETECTOR

Interestingly the sensor can be adjusted using the 2 pots on it which you can see underneath

Adjust the distance potentiometer clockwise rotation, increased sensing distance (about 7 meters), on the contrary, the sensing distance decreases (about 3 meters).
Adjust the delay potentiometer clockwise rotation sensor the delay lengthened (300S), on the contrary, shorten the induction delay (5S).

Induction module needs a minute or so to initialize. During initializing time, it will output 0-3 times. One minute later it comes into standby.

Schematic

Here is a schematic and layout drawn up using fritzing

Code

The code is written in python and requires the Rpi.GPIO library to be present. I called this pir.py

[codesyntax lang=”python”]

import time
import RPi.GPIO as io
io.setmode(io.BCM)
 
pir = 18
 
io.setup(pir, io.IN)         # activate input
 
while True:
	if io.input(pir):
		print("INTRUDER, INTRUDER, INTRUDER!")
	time.sleep(0.5)

[/codesyntax]

 

Run this by typing the following on the command line

[codesyntax lang=”bash”]

sudo python pir.py

[/codesyntax]

Here is the example running and you can see the sensor detecting me moving in front of it

 

Link

A low cost sensor that can easily be picked up for about $2 each

HC-SR501 Adjust IR Pyroelectric Infrared PIR Module Motion Detector Sensor