Saturday, 23 July 2011

Password(code) Based Digital Locking System Using Microcontroller 89C52/89S52

If you are a beginner in making micro controller projects then this mini project
might just work for you. It's very simple and anybody can make it. The aim
of the project is quite predictable from the title itself-you enter a wrong password
the application wont work(in this case led is used as the application) and on correct
entering of the password, the application as in this case "led" will glow.In this Digital locking system project you will learn more about interfacing keypad and 16x2 LCD to your micro controller along with the code.

components required

For this project you will need the following components:
  • 1 microcontroller 89C52(89S52 will also do)
  • 1 potentiometer-10k
  • 2 ceramic capacitors-22pF
  • 1 switch(button for reset purpose)
  • 1 electrolytic capacitor-10uF,25V
  • 1 crystal oscillator-11.0592MHz
  • 16x2 LCD display
  • 1 resistor-10k
  • 1keypad(here, i have used a calculator keypad.In proteus you can find it by typing keypad-smallcalc)
  • 1 led
  • 1 330 ohm resistor

Schematic diagram

Since this project has been made in proteus software you must have a prior knowledge of it. If you are unaware of the software here is a tutorial which i recommended in one of my previous articles.

The connection of the circuit is explained below:

  • Port 1 of the microcontroller is used as the output port
  • Port 2 of the microcontroller is used as the output port
  • Port 3 of the microcontroller is used as the input port.
  • The LCD is connected to port 2 since output is displayed on LCD
  • The led is connected to port 1 which is our application in this project
  • The keypad is connected to port 3
  • Other components like the crystal and switch are connected for the working of the microcontroller ( minimum circuitry required for proper working of the microcontroller).


As soon as the power supply is provided to the microcontroller "password based" will be shown on the screen.This will remain for a second and after that "enter password" will be displayed as shown below.

The "ENTER PASSWORD " statement will remain for a second and then it will vanish.At this point you will have to enter password which will be shown in terms asterisk " **** ". 

The coding of the micro-controller is done such that only four numbers can be used to enter password. If you want to increase the length of the password you can do that by adding loops in the coding which will be dealt later. Here, in this project the password is set as 1234. when this password is entered the LCD will display "correct password" as shown below and the LED will turn on which is connected at port 1. you can set your own password by changing the password in the code.

If you want to set your password using the operators like " + ", " -" etc you can do it by setting the password in the code as follows:

  • for " ON/C " =16
  • for " + " =10
  • for " - " =14
  • for " = " =15
  • for " x " =11
  • for " ÷ " =13


The programming of the microcontroller is done using keil compiler.The codings for this project is explained below:

#include "REGX51.H"
#include "delay.h" /*the header file of delay is added*/
#include "lcd.h" /*the header file of LCD is added*/
#include "keypad.h" /*the header file of keypad is added*/
#define relay P1_7;
void main()
int first_key,second_key,third_key,fourth_key;
P1=0X00; /*port 1 is defined as the output port*/
P2=0x00; /*port 2 is defined as the output port*/
P3=0xff; /*port 3 is defined as the input port*/
LCD_INIT();/* the LCD display is initialized */
delay_sec(1); /* provides a delay of 1 second */
LCD_CLEAR(); /*clears the LCD display*/
LCD_STRING("*"); /*when any key is pressed display it as " * " */
LCD_STRING("*"); /* by adding another while loop you can further increase the length of your password */
if((first_key==1)&&(second_key==2)&&(third_key==3)&&(fourth_key==4))/*here, the password set is 1234. you can change the password over here.if you have increased your password length see that you also make changes in the If loop over here i.e by adding further &&fifth_key=....&& sixth_.. and so on */
LCD_STRING("Correct Password");
P1_2=1; /* if correct password is entered make P1_2 high which will turn on the led */
LCD_STRING("Incorrect Password");
} }

download files

You can download all the hex file, schematic diagram and codes over here:

schematic diagram


the .hex file

Instead of LED you can use any other application like motor which works using a relay or a buzzer and you can go on with many other application. If you have any questions with regards to the project or would like to improve this project further please feel free to comment.


Arindam Bose said...

where can I find following header files:
These are not included in Keil compiler.
please help me...

Unknown said...

This program is full of errors.
In keil compiler i got 106 errors. please upload the error free programme.
I would be very thankfull.

Unknown said...

this program is error

Deeewaaa said...

what if I want to change the password automaticcaly from pressing the keypad, I want to reset the current password and replace it with new one from keypad not by changing the password in code?

Unknown said...

really it is full of errors??

Unknown said...

bro please send me the code and simulation on

Unknown said...

Ur project is very simple and easy for us....please can u send me a perfect code for it,please it is necessary....

Anonymous said...

Good Project. Interesting.... Hi, Engineers Garage is also the website which is only for Electronics and Electrical Engineers. Where students can find various Projects ideas and tutorials on Microcontroller, Electric Circuits and more. Let’s Check out the website Engineers Garage

Unknown said...

You have discussed an interesting topic that every body should know. Very well explained with examples. i have found a similar websiteHigh Security Key visit the site to know more about Home - Securam

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