Door locks code security
A 4x4 matrix keypad and a 16x2 LCD have been used here. Keypad and LCD are very commonly used input
& output devices, respectively. A four digit predefined password needs to
be specified the user. This password is stored in the system.
While unlocking, if the entered
password from keypad matches with the stored password, then the lock opens and
a message is displayed on LCD. Also an output pin is made high to be used for
further purpose.
The connections in the circuit are as following: port P0 of
microcontroller AT89C51 is used as data input port pin P0^4,P0^5,P0^6,P0^7
which is connected to data
pinsD4,D5,D6,D7 of LCD. P0^2 and P0^3 pins of microcontroller are connected to
control pins RS EN of LCD. Port P1 is used to take input from keypad. P0^7 has
been used as lock output pin of controller.
As the program starts, string ‘Enter Password’ is displayed on
LCD. The keypad is scanned for pressed digits one by one. Every time, row and
column of the key pressed is detected and a ‘*’ is displayed on LCD
corresponding to the entered number. After the four digits are entered,
the user is prompted to ‘Confirm Password’ and again the input is taken through
LCD. If the passwords do not match, a message is displayed to indicate ‘Wrong
Password’; otherwise the user is prompted to unlock the device.
To unlock, user needs to ‘Enter Password’ through keypad. Again
the keypad is scanned for pressed keys and corresponding digits are identified.
The passkey is displayed as ‘*****’ on the LCD screen. After the five digits
are entered, they are compared with the pre-set password. If all the four
digits match with set password, LCD displays ‘Lock Open’ and the lock output
pin goes high. If the security code is wrong, ‘Wrong Password’ is sent to be
displayed on LCD. The system gets locked if more than three attempts are
made with wrong password to open the electronic lock. The system needs to be
reset in such a case.
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