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Arduino UNO-Based Password-Protected Door Lock System with LCD Display and Keypad

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Circuit Documentation

Summary

This circuit is designed to control a 12V solenoid lock using an Arduino UNO, a 4x4 membrane matrix keypad, an LCD I2C display, a 1-channel relay module, a red pushbutton, and a 12V power supply. The user can unlock the door by entering a correct password on the keypad or by pressing the exit button. The status and instructions are displayed on the LCD.

Component List

  1. Arduino UNO

    • Description: Microcontroller board based on the ATmega328P.
    • Pins: UNUSED, IOREF, Reset, 3.3V, 5V, GND, Vin, A0, A1, A2, A3, A4, A5, SCL, SDA, AREF, D13, D12, D11, D10, D9, D8, D7, D6, D5, D4, D3, D2, D1, D0

  2. LCD I2C Display

    • Description: 16x2 character LCD display with I2C interface.
    • Pins: GND, VCC, SDA, SCL

  3. 4X4 Membrane Matrix Keypad

    • Description: Keypad with 4 rows and 4 columns.
    • Pins: R1, R2, R3, R4, C1, C2, C3, C4

  4. 1 Channel Relay 5V

    • Description: Relay module for switching high voltage devices.
    • Pins: VCC, GND, IN, NC, COM, NO

  5. 12V Solenoid Lock

    • Description: Electromechanical lock that operates on 12V.
    • Pins: VCC, GND

  6. Red Pushbutton

    • Description: Pushbutton switch with 4 pins.
    • Pins: Pin 2, Pin 1, Pin 3, Pin 4

  7. 12V Power Supply

    • Description: Power supply providing 12V output.
    • Pins: +, -

  8. Resistor

    • Description: 10k Ohm resistor.
    • Pins: pin1, pin2

Wiring Details

Arduino UNO

LCD I2C Display

4X4 Membrane Matrix Keypad

1 Channel Relay 5V

12V Solenoid Lock

Red Pushbutton

12V Power Supply

Resistor

Documented Code

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

// Define the pins
const int relayPin = 13;       // Pin connected to the relay module
const int exitButtonPin = 12;  // Pin connected to the exit button

// LCD setup: I2C address, columns, rows
LiquidCrystal_I2C lcd(0x27, 16, 2); // 0x27 is the typical I2C address, 16 columns, 2 rows

// Keypad setup
const byte ROWS = 4; // Four rows
const byte COLS = 4; // Four columns
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};    // Connect to the row pinouts of the keypad
byte colPins[COLS] = {5, 4, 3, 2};    // Connect to the column pinouts of the keypad

// Initialize the Keypad
Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);

// Password setup
String password = "1234"; // Correct password
String input = "";        // Variable to store user input

// Exit button debounce variables
bool exitButtonState = LOW;          // Current state of the exit button
bool lastExitButtonState = LOW;      // Previous state of the exit button
unsigned long exitButtonLastTime = 0; // Last time the button was toggled
const unsigned long debounceDelay = 50; // Debounce time in milliseconds

void setup() {
  // Initialize the relay and exit button pins
  pinMode(relayPin, OUTPUT);
  pinMode(exitButtonPin, INPUT_PULLUP); // Configure the exit button with an internal pull-up resistor
  digitalWrite(relayPin, LOW);          // Ensure relay is OFF initially

  // Initialize the LCD
  lcd.begin(16, 2);       // 16 columns, 2 rows
  lcd.backlight();        // Turn on the backlight
  lcd.print("Enter Password:"); // Display initial message

  // Begin Serial Monitor (optional for debugging)
  Serial.begin(9600);
}

void loop() {
  handleExitButton(); // Check and handle the exit button

  // Check keypad input
  char key = keypad.getKey(); // Get keypress
  if (key) {
    if (key == '*') { // Clear input if '*' is pressed
      input = ""; // Clear input
      lcd.clear();
      lcd.print("Input Cleared!");
      delay(1000);
      lcd.clear();