Smart door lock

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 AngularServo, Button, LED
from time import sleep

bolt = AngularServo(17)          # 0 degrees = bolt in, 90 degrees = bolt out
button = Button(27)
red = LED(23)
green = LED(22)

def lock():
    bolt.angle = 0
    red.on()
    green.off()
    print("Door LOCKED")

def unlock():
    bolt.angle = 90
    red.off()
    green.on()
    print("Door UNLOCKED")

lock()
while True:
    button.wait_for_press()
    unlock()
    sleep(5)                     # stay unlocked for 5 seconds
    lock()

How the code works

• lock() and unlock() hold all the steps of one action, so the main loop stays short and easy to read.
• wait_for_press() pauses the program until the button is pressed. This does not waste power.
• After 5 seconds the code calls lock() again, so the door can never stay open by mistake.

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.