Security Keypad For Garage Door Opener

Project Completed: September 1999

Introduction

Our electric garage door opener was having trouble distinguishing between the remote control signal and solar flares (or so we suspect). As a result our garage door would open and close at will. I disconnected the RF receiver and the problem went away, but then we couldn't get into the garage from the outside. The security keypad project was born.

Requirements

The keypad had to be hack proof and vandal proof.
It could not fail, even if someone took a hammer to the keypad or ripped it off the wall and shorted all the wires together.
The security code had to be easy to enter, easy to start over if a mistake was made and easy to change (if the current password was known).
It had to have a back door if the password was lost or forgotten.

The keypad is from an old telephone. The hole below the keypad houses a piezo speaker. There is no other electronics at the keypad, so no one can break in by vandalism. And if all the wires are shorted together, it will not blow the controller board.

The controller board is where the real action is. A PIC16F84 microcontroller runs the system. It runs on 5V supplied from where the RF receiver used to be. It uses an RC oscillator and interfaces to the garage door opener with a transistor (close a loop with the transistor which basically simulates a button). The firmware was written entirely in assembler. I put an extra requirement on the firmware design: run like an RTOS (Real Time Operating System). It's not a true RTOS but the sections of code do not get stuck waiting for events to happen.

Documentation

For security reasons I have decided not to post the source code or circuit schematic.

Pictures

Here is the controller that sits just above the garage door opener (inside the garage of course):

Last Updated: December 16, 2001