Arduino Password Door Lock with Keypad and LCD

جدول المحتويات

In this tutorial, we will build an Arduino Password Door Lock using a 4×4 keypad, a 16×2 LCD with I2C module, and a small SG90 servo motor. This project demonstrates how to create a simple electronic lock where you enter a password on the keypad, and the servo unlocks or locks the door.

The Arduino Password Door Lock is a perfect beginner project because it teaches you:

How to connect a keypad and LCD display to Arduino.
How to write code for password handling.
How to control a servo motor for mechanical movement.

Components Required

To build this project, you need:

Arduino Uno (or compatible board)
4×4 Matrix Keypad (8 pins)
16×2 LCD Display with I2C adapter
SG90 Servo motor
Jumper wires and breadboard
A small door lock or latch (for demo setup)

Circuit Diagram of Arduino Password Door Lock

The wiring is simple:

LCD I2C module → SDA to A4, SCL to A5, VCC to 5V, GND to GND.
Keypad rows → Arduino pins D9, D8, D7, D6.
Keypad columns → Arduino pins D5, D4, D3, D2.
Servo signal → D10, VCC to 5V, GND to GND.

! Tip: Use a separate 5V power supply for the servo motor if possible, because USB power is often not enough.

Arduino Code for Password Door Lock

Below is the full code. It allows you to:
- Enter a password and press # to unlock.
- Door remains open.
- LCD shows: “Enter * to close”.
- When you press *, the servo closes the door again.

/**
Password Door Lock
 */

#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <Keypad.h>
#include <Servo.h>

// LCD
#define LCD_ADDR 0x27
LiquidCrystal_I2C lcd(LCD_ADDR, 16, 2);

// Servo
#define SERVO_PIN 10
#define LOCK_ANGLE   0
#define UNLOCK_ANGLE 90
Servo lockServo;

// Keypad
const byte ROWS = 4;
const byte COLS = 4;
char keys[ROWS][COLS] = {
  {'1','2','3','A'},
  {'4','5','6','B'},
  {'7','8','9','C'},
  {'*','0','#','D'}
};
byte rowPins[ROWS] = {9, 8, 7, 6};
byte colPins[COLS] = {5, 4, 3, 2};
Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);

// Password
String PASSWORD = "1234";
String input = "";
bool doorUnlocked = false;

void lcdPromptLocked() {
  lcd.clear();
  lcd.setCursor(0,0);
  lcd.print("Enter Password");
  lcd.setCursor(0,1);
  lcd.print("and #");
}

void lcdPromptUnlocked() {
  lcd.clear();
  lcd.setCursor(0,0);
  lcd.print("Door is OPEN");
  lcd.setCursor(0,1);
  lcd.print("Enter * to close");
}

void lockDoor() {
  lockServo.write(LOCK_ANGLE);
  doorUnlocked = false;
  lcdPromptLocked();
  input = "";
}

void unlockDoor() {
  lockServo.write(UNLOCK_ANGLE);
  doorUnlocked = true;
  lcdPromptUnlocked();
  input = "";
}

void wrongPasswordMsg() {
  lcd.clear();
  lcd.setCursor(0,0);
  lcd.print("Wrong Password");
  lcd.setCursor(0,1);
  lcd.print("Try again");
  delay(1500);
  lcdPromptLocked();
  input = "";
}

void handleKey(char k) {
  if (doorUnlocked) {
    if (k == '*') lockDoor();
    return;
  }
  if (k == '#') {
    if (input == PASSWORD) unlockDoor();
    else wrongPasswordMsg();
  } else if (k == '*') {
    input = "";
    lcdPromptLocked();
  } else if (k == 'D') {
    if (input.length() > 0) input.remove(input.length()-1);
  } else {
    if (input.length() < 8) input += k;
  }
  lcd.setCursor(0,1);
  lcd.print(String(input.length(), '*'));
}

void setup() {
  lcd.init();
  lcd.backlight();
  lockServo.attach(SERVO_PIN);
  lockDoor();
}

void loop() {
  char key = keypad.getKey();
  if (key) handleKey(key);
}

Code Breakdown: How the Arduino Password Door Lock Works

1) Libraries and Objects



#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <Keypad.h>
#include <Servo.h>

// LCD
#define LCD_ADDR 0x27
LiquidCrystal_I2C lcd(LCD_ADDR, 16, 2);

// Servo
#define SERVO_PIN 10
#define LOCK_ANGLE   0
#define UNLOCK_ANGLE 90
Servo lockServo;

Brings in the drivers for the I²C LCD, keypad scanning, and the servo.
Creates the lcd and lockServo objects used everywhere.

2) Hardware Configuration (Pins & Angles)


#define LCD_ADDR 0x27
#define SERVO_PIN 10
#define LOCK_ANGLE 0
#define UNLOCK_ANGLE 90

Sets the I²C address (change to 0x3F if your module uses it).
Chooses D10 for the servo signal.
Defines two angles for the mechanical lock positions.

3) Keypad Layout and Wiring


const byte ROWS = 4, COLS = 4;
char keys[ROWS][COLS] = { ... };
byte rowPins[ROWS] = {9, 8, 7, 6};
byte colPins[COLS] = {5, 4, 3, 2};
Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);

Describes the 4×4 keypad character map.
Maps the 4 row pins and 4 column pins to Arduino pins.
The Keypad library handles debouncing and key detection for yo

4) Password State and Variables


String PASSWORD = "1234";
String input = "";
bool doorUnlocked = false;

PASSWORD is the correct code (easy to change).
input stores what the user typed.
doorUnlocked tracks whether the door is open or closed.

5) LCD Helper Screens


void lcdPromptLocked() { ... }     // "Enter Password" / "and #"
void lcdPromptUnlocked() { ... }   // "Door is OPEN" / "Enter * to close"

Shows clear instructions depending on the mode.
Keeps the user interface consistent and readable.

6) Door Control Helpers


void lockDoor() { ... }
void unlockDoor() { ... }

lockDoor(): moves the servo to LOCK_ANGLE, resets state, shows the lock prompt.
unlockDoor(): moves the servo to UNLOCK_ANGLE, sets state to open, shows the “Enter * to close” prompt.

7) Feedback on Wrong Password


void wrongPasswordMsg() { ... }

Displays a short error message.
After a brief delay, it returns to the locked prompt and clears the input.

8) Central Input Logic (handleKey)


void handleKey(char k) { ... }

This is the brain of the Arduino Password Door Lock:

If door is open: only * is accepted to close the door (safety and clarity).
If door is locked:
- # → compares input with PASSWORD. If they match, unlock; else show error.
- * → clears the entire input.
- D → backspace (delete last character).
- Digits / A B C → append to input until max length (8).
At the end, it masks the input on the LCD (shows **** instead of digits).

9) Setup: One-Time Initialization


void setup() {
  lcd.init(); lcd.backlight();
  lockServo.attach(SERVO_PIN);
  lockDoor();                      // start locked
  // optional welcome screen...
  lcdPromptLocked();
}

Starts the LCD, attaches the servo, and boots in locked mode.
Shows the first prompt: “Enter Password and #”.

10) Loop: Read Keys and React


void loop() {
  char key = keypad.getKey();
  if (key) handleKey(key);
}

Polls the keypad; if a key is pressed, it sends it to handleKey.
Because all logic is in handleKey, the loop() stays simple and stable.

How the Arduino Password Door Lock Works

The LCD shows: “Enter Password and #”.
You type digits on the keypad.
When you press #, the code checks the input.
If the password is correct, the servo rotates to unlock the door.
- LCD shows: “Door is OPEN – Enter * to close”.
The door stays open until you press *.
On pressing *, the servo rotates back to the locked position.

Customize Your Arduino Password Door Lock

Change the password: set PASSWORD = "6789";.
Adjust mechanics: tune LOCK_ANGLE and UNLOCK_ANGLE to match your latch.
Improve power: use an external 5 V / ≥1 A supply for the servo; connect grounds.
Add features:
- EEPROM to save a new password via a simple menu (e.g., A to enter “change mode”).
- Buzzer on wrong attempts.
- Relay for an electronic strike lock or magnetic door lock.

الخاتمة

The Arduino Password Door Lock is a fun and practical beginner project. With just a keypad, LCD, and servo motor, you can build your own electronic security system.

This project is perfect for learning keypad input, LCD display programming, and servo control with Arduino. With a few improvements, you can even turn it into a real home automation system.