This project is a simple security system: Password System.with 4 digits.

It is consist of 3 LEDs that reflect the state security:

RED LED: Closed.

GREEN LED: Open.

Yello LED: Key press LED.

Default Password is 1234 with the ability to reset the it.

Once you entered the old password you can press " * " to start the " Reset Process"

Step 1: Components

In This Project You will NEED:

LED *3
RED, GREEN, YELLOW
Resistors*3
220 Ohm
9V Battery
7805: 5V Regulator
4*4 Keypad
3*4 Keypad may work also
ATmega8: PDIP

Step 2: Circuit Diagram

The following Images shows How to connect the circuit:

Schematic Diagram
Designed by Proteus 8 Professional

PCB Diagram
Designed by Fritzing

Step 3: Code Algorithm

The Code:
The code works as the following:

You have two ways to design your code

Sending 1s to the rows, and check if the columns are 1 or 0

Sending 1s to the columns, and check if the rows are 1 or 0

When there is 1 in the row and the column that means the key is pressed.

Saving the 4 Keys into 4 Variables

then checking whether the password is true or not.

if True: Green LED on
if False: Red LED Blink

To change Password:

Enter the Old Password: Default is 1234
Press " * "
Enter New 4 digits Password
Taa Daa, Password Has Changed

Step 4: Code

#include <mega8.h>

#include <delay.h>


char KeyCheck();

char K0,K1,K2,K3,K;

char P0 = '1',P1 = '2',P2 = '3',P3='4';

char Key;
int i;
void main(void)
{

PORTB=0xff;
DDRB=0x00;

PORTC=0x00;
DDRC=0x7F;

PORTD=0x00;
DDRD=0xff;

while (1)
      {

PORTD = 0x20; 
K0 = KeyCheck();
PORTD = 0x60;
delay_ms(500);PORTD = 0x20;
K1 = KeyCheck();
PORTD = 0x60;
delay_ms(500);
PORTD = 0x20;      
K2 = KeyCheck();
      
PORTD = 0x60;delay_ms(500);
PORTD = 0x20;
      
K3 = KeyCheck();
      
PORTD = 0x60;delay_ms(500);
PORTD = 0x20;
      
if (K0 ==P0 && K1 ==P1 && K2 ==P2 && K3 ==P3)

 {
            
PORTD = 0x80;
            
K = KeyCheck();
           
 delay_ms(20);
            
if (K == '*')
               
 {   
K='0';
                    
PORTD = 0xC0;delay_ms(500);
PORTD = 0x80;
                    
P0 = KeyCheck();
                   
 PORTD = 0xC0;
delay_ms(500);
PORTD = 0x80;
                    
P1 = KeyCheck();
                    
PORTD = 0xC0;
delay_ms(500);
PORTD = 0x80;
                    
P2 = KeyCheck();
                    
PORTD = 0xC0;
delay_ms(500);
PORTD = 0x80;
                    
P3 = KeyCheck();
                    
PORTD = 0xC0;
delay_ms(500);
PORTD = 0x80;
                
}
            
}
     
 else
     
{
      
 for (i =0;i<3;i++)
           
 {
               
 PORTD = 0x20;
               
 delay_ms(300);
                
PORTD = 0x00;
                
delay_ms(300);                            
           
 }
      }
}
}

char KeyCheck()

{
    
Key='X';
    
while (Key == 'X')
   
 {
PORTC = 0b11011111;             
        
if(PINB == 0b11111101)
           
Key = '1';
        
if(PINB == 0b11111011)
           
Key = '2';
        
if(PINB == 0b11110111)
           
Key = '3';   
    
PORTC = 0b11101111;           
        
if(PINB == 0b11111101)             
Key = '4';
        
if(PINB == 0b11111011)
            
Key = '5';
        
if(PINB == 0b11110111)
            
Key = '6';
    
PORTC = 0b11110111;             
        
if(PINB == 0b11111101)
            
Key = '7';
        
if(PINB == 0b11111011)
            
Key = '8';
        
if(PINB == 0b11110111)
            
Key = '9';
    
PORTC = 0b11111011;               
        
if(PINB == 0b11111101)
            
Key = '*';
        
if(PINB == 0b11111011)
            
Key = '0';
        
if(PINB == 0b11110111)
            
Key = '#';