# How to Make a Digital Lock Using Arduino?

- Link: https://studyelectrical.com/2016/11/digital-code-lock-using-arduino.html
- Published: 2016-11-01T15:26:00+00:00
- Author: 

Digital code locks are most common in security systems. An electronic lock or digital
lock is a device which has an electronic control assembly attached to it. They are
provided with an access control system.

This system allows the user to unlock the device with a password. The password is
entered by making use of a keypad. The user can also set his password to ensure 
better protection.

In this project, major components include a keypad, LCD and the controller Arduino.
This article describes the making of an electronic code lock using Arduino.

### Components Required

The following components are required for making the digital code lock

 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

Code lock circuit is constructed around Arduino Uno, using LCD and keypad. 

LCD and keypad forms the user interface for entering the password and displaying
related messages such as “Invalid password”, “Door open”, etc. 

Two LEDs are provided to indicate the status of door whether it is locked or open.
To operate latch/lock we are using Relay which can be connected to the electronic
actuator or solenoid.

![Digital Door Lock using arduino](https://2.bp.blogspot.com/-c8Ii6UX5KoM/WBhLYcr6A3I/
AAAAAAAACDs/9aE5QjahD9Ayo_qbfKUZ6UV7cgv67jKzwCLcB/s1600/digital%2Block.jpg "Digital
Door Lock using arduino")

 Digital Door Lock using Arduino

### Program Code for Arduino Digital Code Lock

The program is constructed using two libraries “LiquidCrystal” and “Keypad”. 

Program have different modules, Setup, Loop, Lock. 

In setup, we initialize all the IO connections and LCD, Keypad. 

In the main loop, we are taking pressed keys in array “code[]”, Once the four digits
are entered we stop accepting keys. 

We are using numeric keys and ‘C’, “=” key. ‘C’ key is used to lock or clear the
display in case the wrong password is entered. 

We can hide the entered password by putting Star character ‘*’.

After entering the password ‘=’ key acts as ok. If the password is the correct door
is kept unlocked for few seconds. If it is incorrect message will be displayed.

### Digital Lock Using Arduino Code

/* 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) }

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