How to setup PIR sensor with Raspberry Pi

Nov 30, 2018

—

In this tutorial, I want to share my experience with the PIR sensor in combination with the Raspberry Pi. First of all, here is a list of all items, which you need, to follow this tutorial.

Raspberry Pi 2 Model B (v1.1) (Digitec)
- set up with Raspbian Desktop
Speaker with 3.5mm Line-In
3.5mm Line-In cable (Male-Male)
Jumper Cables (Female-Female) (Digitec)
Adafruit PIR (passive infrared sensor) Sensor (Digitec | Amazon)

I have used an old Raspberry Pi 2 Model B for this experiment. But it also works with a newer model. You may have to change the GPIO numbers according to your board version. To check out type:

sudo pinout

After you have checked your board GPIOs, you are now ready to setup.

Wiring the motion sensor with Raspberry Pi

I have started connecting the motion sensor with the Raspberry Pi via the Jumper Cables. In that case, you don’t need an external board or to solder it. We have three cables to connect. The first is the 5V power pin (connected with a red cable). The second is the data pin on the GPIO 23. And last we have the Ground (GND) pin.

Sketch of GPIO pins. Original Source: Raspberry Pi Documentation

On my Raspberry Pi, this will look like this:

Connect the speaker with the Raspberry Pi

This is really simple, just plug in the audio cable on the Raspberry Pi and the other end to the speaker. This was an easy step, right?

Now we also have to force the output through this port. For that open a terminal in the Raspbian OS and enter

sudo raspi-config

There we will find the menu Advanced options > Audio and then select Force 3.5mm ('headphone') jack. Now reboot the system and all the sound output will be coming from this port.

Code the Pi

Now we are coming to the programming part. Since we have connected the PIR to the GPIO 23, we are now able to get access to this pin through a python script. First, create a new file on your Pi Desktop called start.py and paste the following script:

	import RPi.GPIO as GPIO
	import time
	import os

	# Some GPIO standard settings
	GPIO.setwarnings(False);
	GPIO.setmode(GPIO.BCM);

	# Your GPIO number according to the GPIO number list of your Raspberry Pi
	PIN_NUMBER = 23;

	# Setup the GPIO instance with your number above and mark it as Input device
	GPIO.setup(PIN_NUMBER, GPIO.IN, pull_up_down = GPIO.PUD_DOWN);

	# Turn up the volume
	os.system("amixer set PCM -- 94%")

	inc = 0; # Delay counter

	# Run this code infinitely
	while True:
	time.sleep(1); # Sleep to relieve the PIR sensor
	inc = inc + 1; # Count up for the delay
	i = GPIO.input(PIN_NUMBER); # Get the response of your PIR
	print "Status ", inc,": ", i;

	# If last alarm was played at least 30 seconds ago and
	# sensor has detected a motion
	if inc > 30 and i == 1:
	print "Play";
	os.system("aplay alarm.wav"); # Play the wav sound
	inc = 0; # Reset delay counter

view raw start.py hosted with

by GitHub

Audio file

Put also in the same directory your WAV file. Please make sure that you are using a WAV file because the command aplay only works with these files. Otherwise, you have to setup mpg321 to play MP3 files for example.

Start the script

Now you are able to start the script by typing the following command:

python start.py

End product

So now, your motion sensor with speaker output is ready. You can adjust the sensitivity and time output by turn the orange screws on the PIR sensor with a screwdriver.