Password Based Door Lock System using 8051 Microcontroller

Traditional lock systems using mechanical lock and key mechanism are being replaced by new advanced techniques of locking system. These techniques are an integration of mechanical and electronic devices and highly intelligent. One of the prominent features of these innovative lock systems is their simplicity and high efficiency.

Here we develop an electronic code lock system using 8051 microcontroller, which provides control to the actuating the load. It is a simple embedded system with input from the keyboard and the output being actuated accordingly.

This system demonstrates a password based door lock system wherein once the correct code or password is entered, the door is opened and the concerned person is allowed access to the secured area. Again if another person arrives it will ask to enter the password. If the password is wrong then door would remain closed, denying the access to the person.

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Principle Behind the Circuit:

The main component in the circuit is 8051 controller. In this project 4×3 keypad is used to enter the password. The password which is entered is compared with the predefined password.

If the entered password is correct then the system opens the door by rotating door motor and displays the status of door on LCD. If the password is wrong then door is remain closed and displays “pwd is wrong” on LCD.

Circuit Diagram of Password Based Door Lock System using 8051 Microcontroller:

Password Based Door Locking System Project Required Components:

Hardware Requirements:

1. at89c51 controller
2. 8051 programming board
3. Programming cable
4. DC battery or 12V,1A adaptor
5. 4×3 matrix keypad
6. 16×2 LCD
7. 5V Relay
8. DC motor
9. BC 547 Transistor
10. 10k, 330 Ω  resistor (1/4 watt)
11. 10uF electrolytic capacitor
12. 33pF capacitors – 2
13. 12MHz Crystal
14. Pot 10k (1/4 watt) – 1
15. connecting wires

Software Requirements:

1. Keil compiler
2. Flash magic
3. Proteus

Electronic Code Lock System Circuit Design:

Password based door lock circuit design uses five major components – a Microcontroller, a Relay, a DC motor, a 4×3 matrix keypad and a LCD. Here AT89C51 microcontroller is used and it is an 8-bit controller. This controller requires a supply voltage of +5V DC. In order to provide regulated 5V DC voltage to the controller we need to use 7805 power supply circuit. We can use 9V DC battery or 12V, 1A adaptor as a power source.

Reset Circuit Design: The reset pin of the microcontroller is kept active till the power supply is in the specified range and a minimum oscillation level is maintained.  In other words to ensure the supply voltage does not falls below the threshold level of 1.2V and the reset pulse width is greater than 100ms (recommended for 89C51),  we select the values of resistor and capacitor such that RC >=100ms.  Here we select a 10K resistor and a 10uF electrolyte capacitor.

Oscillator Circuit Design: A crystal oscillator is used to provide external clock signal to the microcontroller. To ensure smooth operation, we connect two ceramic capacitors ranges from 20pF to 40pF. This crystal oscillator is connected between pin 18 and 19 of the microcontroller.

Compilation of Microcontroller Code: Once the circuit is designed and drawn on a piece of paper, the next step is to write and compile the code. Here we select the Kiel uVision software to write the program in C language.

Prior to writing the code, general steps needs to be followed like creating a new project and selecting the target device or the required microcontroller. Once the code is written, we saved it with .c extension and then added it to the source file group under the target folder.  The code is then compiled by pressing F7 key.

Once the code is compiled, a hex file is created.  In the next step, we use Proteus software to draw the circuit. The code is dumped into the microcontroller by right clicking on the IC and then adding the hex file.
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