How to Make a Digital Lock Using Arduino?

1. Arduino Uno
2. 16×2 LCD Display
3. 4×4 keypad
4. Relay
5. 1K Resistors Qty. 3
6. BC548
7. LEDs

Digital Code Lock Circuit

/* Digital Code Lock Demo */
#include <Keypad.h>
#include <LiquidCrystal.h>
// initialize the library with the numbers of the interface pins
LiquidCrystal lcd (9, 8, 7, 6, 5, 4);
const byte ROWS = 4; //four rows
const byte COLS = 4; //four columns
//define the cymbols on the buttons of the keypads
char hexaKeys [ ROWS ][ COLS ] = {
{‘7′,’8′,’9′,’/’},
{‘4′,’5′,’6′,’*’},
{‘1′,’2′,’3′,’-‘},
{‘C’,’0′,’=’,’+’}
};
byte rowPins [ ROWS ] = {3, 2, 19, 18}; //connect to the row pinouts of the keypad
byte colPins [ COLS ] = {17, 16, 15, 14}; //connect to the column pinouts of the keypad
//initialize an instance of class NewKeypad
Keypad customKeypad = Keypad ( makeKeymap ( hexaKeys ), rowPins , colPins , ROWS ,
COLS );
const int LED_RED =10; //Red LED
const int LED_GREEN =11; //Green LED
const int RELAY =12; //Lock Relay or motor
char keycount =0;
char code [4]; //Hold pressed keys
//=================================================================
// SETUP
//=================================================================
void setup (){
pinMode ( LED_RED , OUTPUT );
pinMode ( LED_GREEN , OUTPUT );
pinMode ( RELAY , OUTPUT );
// set up the LCD’s number of columns and rows:
lcd . begin (16, 2);
// Print a message to the LCD.
lcd . print (“Password Access:”);
lcd . setCursor (0,1); //Move coursor to second Line
// Turn on the cursor
lcd . cursor ();
digitalWrite ( LED_GREEN , HIGH ); //Green LED Off
digitalWrite ( LED_RED , LOW ); //Red LED On
digitalWrite ( RELAY , LOW ); //Turn off Relay (Locked)
}//
=================================================================
// LOOP
//=================================================================
void loop (){
char customKey = customKeypad . getKey ();
if ( customKey && ( keycount <4) && ( customKey !=’=’) && ( customKey !=’C’)){
//lcd.print(customKey); //To display entered keys
lcd . print (‘*’); //Do not display entered keys
code [ keycount ]= customKey ;
keycount ++;
}
if(customKey == ‘C’) //Cancel/Lock Key is pressed clear display and lock
{
Lock (); //Lock and clear display
}
if(customKey == ‘=’) //Check Password and Unlock
{
if(( code [0]==’1′) && ( code [1]==’2′) && ( code [2]==’3′) && ( code [3]==’4′)) //Match the
password. Default password is “1234”
{
digitalWrite ( LED_GREEN , LOW ); //Green LED Off
digitalWrite ( LED_RED , HIGH ); //Red LED On
digitalWrite ( RELAY , HIGH ); //Turn on Relay (Unlocked)
lcd . setCursor (0,1);
lcd . print (“Door Open “);
delay (4000); //Keep Door open for 4 Seconds
Lock ();
}
else
{
lcd . setCursor (0,1);
lcd . print (“Invalid Password”); //Display Error Message
delay (1500); //Message delay
Lock ();
}
}
}
//=================================================================
// LOCK and Update Display
//=================================================================
void Lock ()
{
lcd . setCursor (0,1);
lcd . print (“Door Locked “);
delay (1500);
lcd . setCursor (0,1);
lcd . print (” “); //Clear Password
lcd . setCursor (0,1);
keycount =0;
digitalWrite ( LED_GREEN , HIGH ); //Green LED Off
digitalWrite ( LED_RED , LOW ); //Red LED On
digitalWrite ( RELAY , LOW ); //Turn off Relay (Locked)
}