Password Based Door Locking (AT89C2051)

Security is a prime concern in our day-today life. Everyone wants to be as much secure as possible. An access control for doors forms a vital link in a security chain.

The microcontroller based Door locker is an access control system that allows only authorized persons to access a restricted area. The system is fully controlled by the 8 bit microcontroller AT89C2051 which has a 2Kbytes of ROM for the program memory. The password is stored in the EPROM so that we can change it at any time.

The system has a Keypad by which the password can be entered through it. When the entered password equals with the password stored in the memory then the relay gets on and so that the door is opened. If we entered a wrong password for more than three times then the Alarm is switched on.

The default password is 1111 and you can change the password by dialing 1234, old password, new password #button. for example if you want to change the password from the default to 4523 then dial 123411114523# after dialing you can hear a beep sound which confirm the operation goes successful.

There are two relays one to open the door and other to close the door. There is an button which should be placed inside the door so that the person inside can open/close the door.

The passwords are stored on the EEPROM chip. The EEPROM works on I2C technology. please refer the tutorials for the I2C interface.

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Circuit Diagram:


Download the Source code from here:
Download the PCB from here: