Software

Author Gravatar Image SIMON MONK

The program for this project just loops round printing a message every time motion is detected, or the magnet is moved away from the door.

The program uses the Rpi.GPIO library. See Lesson 4.

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import time
import RPi.GPIO as io
io.setmode(io.BCM)

pir_pin = 18
door_pin = 23

io.setup(pir_pin, io.IN)         # activate input
io.setup(door_pin, io.IN, pull_up_down=io.PUD_UP)  # activate input with PullUp

while True:
    if io.input(pir_pin):
        print("PIR ALARM!")
    if io.input(door_pin):
        print("DOOR ALARM!")
    time.sleep(0.5)

The program sets the pir_pin to be just a plain old input. This is because the PIR sensor has a digital output of either 3.3V or 0V. By contrast, the door_pin, since it is a switch does not generate a voltage for a digital input. So, that input pin uses the extra argument (pull_up_down=io.PUD_UP). This activates an internal resistor that makes the input HIGH (pulled-up) unless something stronger (like a switch connecting it to GND) pulls it LOW.

The loop then reads each of the inputs in turn and prints a message appropriately. Remember that the door switch warning will be activated when the magnet is removed from the sensor rather than the other way around.

Last updated on 2014-04-05 at 07.22.28 PM Published on 2013-02-13 at 03.35.59 PM