DIY RFID Door Lock System using Arduino

#include <LiquidCrystal_I2C.h>
#include <MFRC522.h>
// Define RC522 RFID module pins
#define RST_PIN 9   // Reset pin
#define SS_PIN 10   // Slave Select pin
// Initialize MFRC522 instance
MFRC522 rfid(SS_PIN, RST_PIN);
// Initialize the I2C LCD (set the I2C address, usually 0x27 or 0x3F)
LiquidCrystal_I2C lcd(0x27, 16, 2);
void setup() {
 // Initialize SPI and RC522 module
 Serial.begin(9600);
 SPI.begin();
 rfid.PCD_Init();
 // Initialize the LCD
 lcd.init();
 lcd.backlight();
 lcd.setCursor(0, 0);
 lcd.print("Scan RFID Card");
 Serial.println("Scan RFID Card");
}
void loop() {
 // Check if a new RFID card is present
 if (!rfid.PICC_IsNewCardPresent()) {
   return;
 }
 // Check if the RFID card can be read
 if (!rfid.PICC_ReadCardSerial()) {
   return;
 }
 // Clear LCD and display the UID
 lcd.clear();
 lcd.setCursor(0, 0);
 lcd.print("Card UID:");
 Serial.print("Card UID: ");
 // Print the UID on the LCD
 lcd.setCursor(0, 1);
 for (byte i = 0; i < rfid.uid.size; i++) {
   if (rfid.uid.uidByte[i] < 0x10) {
     lcd.print("0"); // Add leading 0 for single-digit hex
     Serial.print("0x0");
   }
   lcd.print(rfid.uid.uidByte[i], HEX); // Print UID byte in HEX format
   Serial.print("0x");
   Serial.print(rfid.uid.uidByte[i], HEX);
   if (i < rfid.uid.size - 1) {
     lcd.print(" "); // Add space between bytes
     Serial.print(", ");
   }
   delay(1000);
 }
 // Halt communication with the card
 rfid.PICC_HaltA();
 // Wait for 10 seconds before clearing the LCD
 delay(10000);
 lcd.clear();
 lcd.setCursor(0, 0);
 lcd.print("Scan RFID Card");
 Serial.println("\n");
 Serial.println("Scan RFID Card");
}
#include <MFRC522.h>
#include <LiquidCrystal_I2C.h>
// Define RC522 pins
#define RST_PIN 9
#define SS_PIN 10
// Relay pin
#define RELAY_PIN 8
// Initialize MFRC522 instance
MFRC522 rfid(SS_PIN, RST_PIN);
// Initialize LCD (address 0x27 may vary)
LiquidCrystal_I2C lcd(0x27, 16, 2);
// Authorized UID (replace with your tag's UID)
byte authorizedUID[] = {0x69, 0xA9, 0x81, 0x5A};
// Door status
bool doorLocked = true;
void setup() {
 // Initialize SPI and RC522
 SPI.begin();
 rfid.PCD_Init();
 // Initialize LCD
 lcd.init();
 lcd.backlight();
 // Set up relay pin
 pinMode(RELAY_PIN, OUTPUT);
 // Display startup message
 lcd.setCursor(0, 0);
 lcd.print("RFID Door Lock");
 delay(2000);
 lcd.clear();
 lockDoor(); // Start with door locked
}
void loop() {
 // Check if a new RFID card is present
 if (!rfid.PICC_IsNewCardPresent()) {
   return;
 }
 // Check if the RFID card can be read
 if (!rfid.PICC_ReadCardSerial()) {
   return;
 }
 // Display scanned UID
 lcd.clear();
 lcd.setCursor(0, 0);
 lcd.print("Scanning...");
 delay(2000);
 // Compare scanned UID with authorized UID
 if (isAuthorized(rfid.uid.uidByte, rfid.uid.size)) {
   lcd.setCursor(0, 1);
   lcd.print("Access Granted!");
   delay(2000);
   unlockDoor(); // Lock or unlock the door
 } else {
   lcd.setCursor(0, 1);
   lcd.print("Access Denied!");
   delay(2000);
   lockDoor();
 }
 // Halt communication with the card
 rfid.PICC_HaltA();
}
// Function to check if UID matches authorized UID
bool isAuthorized(byte *uid, byte size) {
 if (size != sizeof(authorizedUID)) {
   return false;
 }
 for (byte i = 0; i < size; i++) {
   if (uid[i] != authorizedUID[i]) {
     return false;
   }
 }
 return true;
}
// Function to lock the door
void lockDoor() {
 digitalWrite(RELAY_PIN, LOW); // Turn OFF relay (lock engaged)
 doorLocked = true;
 lcd.clear();
 lcd.setCursor(0, 0);
 lcd.print("Door Locked");
 delay(2000);
}
// Function to unlock the door
void unlockDoor() {
 digitalWrite(RELAY_PIN, HIGH); // Turn ON relay (unlock door)
 doorLocked = false;
 lcd.clear();
 lcd.setCursor(0, 0);
 lcd.print("Door Unlocked");
 delay(10000); // Keep door unlocked for 5 seconds
 lockDoor();  // Auto-lock after 5 seconds
}