some of you may know the advantages of electric garage doors. they open from the inside of a car even when it’s raining. the disadvantage is the need for the remote control when you want to open that door. with our garage doors it’s similar. the opener is never there when you need to get in.
so i built myself a keypad opening system.
unlike some systems you can buy for about the same money, the electronic brain of the system does not lie behind the keypad itself. it is mounted on the inside so no one can access it from the outside by just loosening some screws. all there is are the 7 pins for the keypad and 2 pins for the led. shortening wires will just be interpreted as keystrokes and will not open the door.
what about trying combinations? there are about 111110000 possible combinations regarding a possible key from 4 to 8 digits. the keypad does not accept any input for 5 minutes after 5 wrong tries. so let’s say one guesses the key half way through all possible keys: 111110000/2 = 55555000. one try per minute (5 tries, 5 minute lockout). one had to try 105 years 254 days 20 hours and a few minutes to guess the correct combination. that’s secure enough for a garage door. 🙂
the brains of the PIGADO (PIn GArage Door Opener) is an arduino pro. some may say an atmega 328 it is a little overdimensioned for this purpose. well — it is. but it’s easy to program and not that expensive. i got it for around 16-17 €. the ease of work with this is worth it. another big advantage of the pro board compared to the regular arduinos is the detachable USB adapter, the FTDI Basic Breakout (~11€). it makes the board cheaper and you can reuse the FTDI Basic for other projects.
the arduino pro can be powered with 4-12 volts. so i reused an old power supply from a mobile phone. not nokia 😉 they use 3.7 volts…
in case you have questions don’t hesitate to leave a comment blow.