Key Less Stealth Abstract

Atmel AVR 2004 Design Contest Project Number A3548 Stealth Keyless Entry System Abstract

Often a ten button keyless entry pad, usually controlling a garage door, is used to provide entry into a home by anyone knowing the numerical entry code. Security problems can develop over time as small amounts of finger dirt and grime collect on the keypad buttons used for the entry code. This along with keypad button wear can make it relatively easy for someone to identify the keypad buttons, and therefore the digits, used for the entry code. Knowing the digits used for the entry code greatly reduces the number of permutations a thief would need to try in order to gain entry to a residence. This system modifies a home’s existing doorbell to become a “hidden” keyless entry system. The doorbell will operate normally unless a secret code is entered via the doorbell button. When the secret code is entered, the doorbell does not ring and the garage door is opened. An Atmel Microcontroller is used to decipher the entered code, compare it with a master code stored in EEPROM, and control opening the garage door when the entered code matches the master. When pushing the doorbell button, the doorbell will be rung as soon as there is a deviation from the master code. This will essentially be immediately to anyone not aware that the doorbell button doubles as a keyless entry system. Old fashioned Morse code is used for entering the secret code. Ugh! Learn the Morse code? One should not be discouraged, as the entire Morse code does not need to be learned to use this system. Only a few letters, perhaps three or four, will be all that is needed. Moreover, the Microcontroller has a wide tolerance on what it accepts for the “dots” and “dashes” of the code. This system even provides the user with options that can be used to practice its operation. When a dumb terminal is connected to the system’s 2400 baud RS-232 output, these options allow the user to: • • •

Print the doorbell button closure times. This is useful if the user wants to modify the software tune parameters that the Microcontroller uses in interpreting the coded input. Print the Morse code characters entered via the doorbell button. This is very useful when first trying out the system. Print out the master code stored in EEPROM as well as print out successes and failures as the user tries out the system.

An option is also provided that allows a chosen master code to be entered into EEPROM by just keying it into the system via the doorbell button. Not knowing that the doorbell button is also a “hidden” keyless entry system does provide a level of security above that obtained with one of those keypad entry systems.

Atmel AVR 2004 Design Contest Project Number A3548 Stealth Keyless Entry System Block Diagram Switch Input

OptoIsolator

ICP

Microcontroller/ Software Switch Debouncer

LED

Morse Element Classifier Reset Circuit

RST

Morse Character Recognizer

RS-232 Driver

Key Matcher Option Jumpers

Output Action

Timing Service Key

Bell Relay Driver

Door Relay Driver

Terminal (optional)

Bell Control

Door Control