Door alarm with a buzzer

Parts in this circuit

Wiring, pin by pin

Red = 5 V, orange = 3.3 V, black = GND, other colours = signals. “Pin” is the position on the 40-pin header; the GPIO number is what the code uses. Power the Pi from a 5.1 V supply and wire with the power off.

Python code (gpiozero)

from gpiozero import Buzzer, Button

buzzer = Buzzer(18)
door = Button(27)          # the button acts as a door switch

print("Door closed. Press and hold to open the door.")

while True:
    door.wait_for_press()          # sleep until the door opens
    print("DOOR OPEN! Alarm!")
    buzzer.beep(0.2, 0.2)          # beep in the background
    door.wait_for_release()        # wait until the door closes
    buzzer.off()
    print("Door closed.")

How the code works

• wait_for_press() makes the program sleep until the button goes down. It uses no CPU while waiting.
• buzzer.beep(0.2, 0.2) starts a beep pattern in the background and the program carries on.
• buzzer.off() stops the beeping when the door closes.

Parts to buy

The links open a search on each store, so you see what is in stock today. Check the model, voltage and price before you order.