Changeable Digital Code Lock using Arduino and Keypad

This will set password “1234” to EEPROM of Arduino.

After running it first time we need to remove this from program and again write the code in to the arduino and run. Now your system will run fine. And for your second time used password is now “1234”. Now you can change it by pressing # button and then enter your current password and then enter your new password. 

When you will enter your password, system will compare your entered password with that password that is stored in EEPROM of arduino. If match is occurred then LCD will show “access granted” and if password is wrong then LCD will “Access Denied” and buzzer continuously beep for some time. And buzzer is also beep a single time whenever user will press any button from keypad.

Programming Description

In code we have used keypad library for interfacing keypad with arduino.

#include <Keypad.h>
#include<LiquidCrystal.h>
#include<EEPROM.h>

const byte ROWS = 4; //four rows
const byte COLS = 4; //four columns

char hexaKeys[ROWS][COLS] = {
  {'1','2','3','A'},
  {'4','5','6','B'},
  {'7','8','9','C'},
  {'*','0','#','D'}
};

byte rowPins[ROWS] = {3, 2, 1, 0}; //connect to the row pinouts of the keypad
byte colPins[COLS] = {4, 5, 6, 7}; //connect to the column pinouts of the keypad

//initialize an instance of class NewKeypad
Keypad customKeypad = Keypad( makeKeymap(hexaKeys), rowPins, colPins, ROWS, COLS); 

We have included LCD library for LCD interfacing and for interfacing EEPROM we have included library EEPROM.h., and then initialized variable and defined pins for components.

#define buzzer 15

LiquidCrystal lcd(13,12,11,10,9,8);

char password[4];

char pass[4],pass1[4];

int i=0;

char customKey=0;

And then we initialized LCD and give direction to pins in setup function

void setup()
{
  lcd.begin(16,2);
  pinMode(led, OUTPUT);
  pinMode(buzzer, OUTPUT);
  pinMode(m11, OUTPUT);
  pinMode(m12, OUTPUT);
  lcd.print("  Electronic ");
  lcd.setCursor(0,1);
  lcd.print("  Keypad Lock ");
  delay(2000);
  lcd.clear();
  lcd.print("Enter Ur Passkey:");
  lcd.setCursor(0,1);

After this we read keypad in loop function

  customKey = customKeypad.getKey();
  if(customKey=='#')
  change();
  if (customKey)
  {
     password[i++]=customKey;
     lcd.print(customKey);
     beep();
  }

And then compare password with save password using string compare method.

 if(i==4)
  {
    delay(200);
    for(int j=0;j<4;j++)
    pass[j]=EEPROM.read(j);
    if(!(strncmp(password, pass,4)))
    {
      digitalWrite(led, HIGH);
      beep();
      lcd.clear();
      lcd.print("Passkey Accepted");
      delay(2000);
      lcd.setCursor(0,1);
      lcd.print("#.Change Passkey");
      delay(2000);
      lcd.clear();
      lcd.print("Enter Passkey:");
      lcd.setCursor(0,1);
      i=0;
      digitalWrite(led, LOW);
    }

This is password change function and buzzer beep function

void change()
{
  int j=0;
  lcd.clear();
  lcd.print("UR Current Passk");
  lcd.setCursor(0,1);
  while(j<4)
  {
    char key=customKeypad.getKey();
    if(key)
    {
      pass1[j++]=key;
      lcd.print(key);

void beep()
{
  digitalWrite(buzzer, HIGH);
  delay(20);
  digitalWrite(buzzer, LOW);
}