3

FORGE

2. Unlock the door by switching the GPIO pin to
   HIGH, which triggers the relay


3. Wait for five seconds to allow time for the
   door to be opened


4. Print another line of text saying the door is
   now being locked again


5. Lock the door again by switching the GPIO pin
   back to LOW

If the data read from the fob isn’t the data we’re
looking for, then we do nothing apart from print a
line of text saying ‘Access Denied’ to the Terminal.
After either outcome, it’s extremely important to
remember to clear out the rfid_presented variable
so that we’re starting afresh next time ready for the
next unlock attempt.
Before those lines of code which control the GPIO
pin will work, you first need to import the RPi.GPIO
module for use in your script, as well as the time
module which will enable the sleep function to work.
To do this, go back to the top of your script and
underneath the two imports you already have, add
these lines:

import RPi.GPIO as GPIO

import time

GPIO.setmode(GPIO.BCM)

GPIO.setwarnings(False)

GPIO.setup(13,GPIO.OUT)

As well as importing the two extra Python
modules you need, this will also configure and
initialise the GPIO pins ready for use.
With your Python script now complete, save and
exit by pressing CTRL+X to exit and then pressing Y
to save changes. Then to load your program, type:

python lock.py

THE MOMENT OF TRUTH – DOES IT WORK?
If you hold the authorised key fob to your reader, you
should immediately hear the relay ‘click’ and if you try
the striker plate, it will allow itself to be opened. After
five seconds, you’ll hear another click and the striker
plate will no longer open. Then try another fob and
you should be met with a blank wall of silence, and an
Access Denied message printed to the Terminal.
That’s all there is to it! You now have a
sophisticated security system for whichever room
(or cupboard!) that you’re securing. What’s more,

since it uses a Raspberry Pi which can be connected

to the internet, it’s full of possibilities for expansion.

You could write an app to unlock the door remotely

by simply toggling the GPIO pin between high and

low, or you could add a keypad to require a PIN to

accompany the NFC tag presented. If you build one

yourself, be sure to share it with us so we can see

what you’ve come up with!

Left

The Python script

prints text to the

Terminal, showing

when the door is

unlocked and locked

again, as well as

when access has

been denied

Below

Once you’re done,

you can install the

electronic striker

plate into the

doorway that you

want to secure with

NFC fob access!