Arduino Project

Arduino RFID Door Lock Project with MFRC522 V2

Course Introduction

In this lesson, we’ll build a 2.0 access-control system using the MFRC522 module, a 1602 LCD, and an active buzzer.

Valid cards light the green LED and play an “access granted” tone; invalid cards light the red LED and trigger a warning alarm.

Note

If this is your first time working with an Arduino project, we recommend downloading and reviewing the basic materials first.

1.1 Install Arduino IDE(Important)
1.2 Introduction of Arduino IDE

Required Components

In this project, we need the following components:

SN	COMPONENT INTRODUCTION	QUANTITY	PURCHASE LINK
1	Arduino UNO R4 Minima/Arduino UNO R4 WIFI	1	BUY
2	USB Type-C cable	1	×
3	Breadboard	1	BUY
4	Wires	Several	BUY
5	I2C LCD 1602	1	BUY
6	MFRC522 Module	1	BUY
7	Active Buzzer	1	×
8	Power Supply Module	1	BUY
9	LED	4	BUY
10	Resistor	1KΩ × 4	BUY

Wiring

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Common Connections:

MFRC522 Module
SDA: Connect to 10 on the Arduino.
SCK: Connect to 13 on the Arduino.
MOSI: Connect to 11 on the Arduino.
MISO: Connect to 12 on the Arduino.
GND: Connect to breadboard’s negative power bus.
RST: Connect to 9 on the Arduino.
3.3V: Connect to breadboard’s passive power bus.

Active Buzzer
＋: Connect to 6 on the Arduino.
－: Connect to breadboard’s negative power bus.

I2C LCD 1602
SDA: Connect to A4 on the Arduino.
SCL: Connect to A5 on the Arduino.
GND: Connect to breadboard’s negative power bus.
VCC: Connect to breadboard’s red power bus.

LED
Connect the LEDs cathode to the negative power bus on the breadboard, and the Green LED anode to the 5 on the Arduino through a 1 kΩ resistor, the Red LED cathode to the 6 on the Arduino through a 1 kΩ resistor.

Writing the Code

Note
You can copy this code into Arduino IDE.
To install the library, use the Arduino Library Manager and search for LiquidCrystal I2C and install it.
To install the library, use the Arduino Library Manager and search for MFRC522 and install it.
Don’t forget to select the board(Arduino UNO R4 WIFI) and the correct port before clicking the Upload button.

  #include <SPI.h>                  // SPI library for RFID communication
#include <MFRC522.h>              // RFID library for MFRC522 module
#include <Wire.h>                 // I2C library for LCD
#include <LiquidCrystal_I2C.h>    // LCD library for I2C-based LCDs

// Pin definitions
#define SS_PIN         10         // RFID SDA (SS) pin
#define RST_PIN        9          // RFID reset pin
#define RED_LED_PIN    4          // Red LED pin
#define GREEN_LED_PIN  5          // Green LED pin
#define BUZZER_PIN     6          // Active buzzer pin

// Create RFID and LCD objects
MFRC522 rfid(SS_PIN, RST_PIN);
LiquidCrystal_I2C lcd(0x27, 16, 2);  // LCD address (change if needed), 16 columns x 2 rows

// UID of the authorized card (replace with your own card UID)
byte authorizedUID[4] = {0x36, 0xE2, 0xC4, 0xF7};

void setup() {
  Serial.begin(9600);          // Start serial monitor for debugging
  SPI.begin();                 // Initialize SPI communication
  rfid.PCD_Init();             // Initialize RFID reader

  lcd.init();                  // Initialize the LCD
  lcd.backlight();             // Turn on LCD backlight

  pinMode(RED_LED_PIN, OUTPUT);
  pinMode(GREEN_LED_PIN, OUTPUT);
  pinMode(BUZZER_PIN, OUTPUT);

  // Set default state: red LED on, LCD shows prompt
  digitalWrite(RED_LED_PIN, HIGH);
  lcd.setCursor(0, 0);
  lcd.print("Scan your card");
}

void loop() {
  // Wait for a new card
  if (!rfid.PICC_IsNewCardPresent() || !rfid.PICC_ReadCardSerial()) return;

  // Print the scanned UID to the Serial Monitor
  Serial.print("Card UID: ");
  for (byte i = 0; i < rfid.uid.size; i++) {
    Serial.print(rfid.uid.uidByte[i] < 0x10 ? " 0" : " ");
    Serial.print(rfid.uid.uidByte[i], HEX);
  }
  Serial.println();

  // Check if the scanned card is authorized
  bool authorized = compareUID(rfid.uid.uidByte, rfid.uid.size);
  showAccessResult(authorized);

  // Stop communicating with the current card
  rfid.PICC_HaltA();
  rfid.PCD_StopCrypto1();
}

// Compare scanned UID with the authorized one
bool compareUID(byte *uid, byte len) {
  if (len != 4) return false;
  for (byte i = 0; i < 4; i++) {
    if (uid[i] != authorizedUID[i]) return false;
  }
  return true;
}

// Display access result and give feedback
void showAccessResult(bool granted) {
  if (granted) {
    // Access granted:
    // Turn off red LED, turn on green LED, show welcome message
    digitalWrite(RED_LED_PIN, LOW);
    digitalWrite(GREEN_LED_PIN, HIGH);
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Welcome!");
    shortBeep();
    delay(1000);

    // Reset to default state
    digitalWrite(GREEN_LED_PIN, LOW);
    digitalWrite(RED_LED_PIN, HIGH);
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Scan your card");

  } else {
    // Access denied:
    // Flash red LED, beep 3 times, show denial message
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Access Denied");
    deniedFeedback(1500);  // Flash and beep for 1.5 seconds

    // Reset to default state
    digitalWrite(RED_LED_PIN, HIGH);
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Scan your card");
  }
}

// Play a short beep (used for access granted)
void shortBeep() {
  digitalWrite(BUZZER_PIN, HIGH);
  delay(200);
  digitalWrite(BUZZER_PIN, LOW);
}

// Flash red LED and beep 3 times over a duration
void deniedFeedback(unsigned long duration) {
  unsigned long start = millis();
  int flashState = LOW;
  unsigned long lastFlash = 0;
  int beepCount = 0;
  unsigned long lastBeep = 0;
  bool beeping = false;

  while (millis() - start < duration) {
    unsigned long now = millis();

    // Toggle red LED every 100ms
    if (now - lastFlash >= 100) {
      flashState = !flashState;
      digitalWrite(RED_LED_PIN, flashState);
      lastFlash = now;
    }

    // Play 3 beeps, each 100ms long, spaced 200ms apart
    if (beepCount < 3) {
      if (!beeping && (now - lastBeep >= 200)) {
        digitalWrite(BUZZER_PIN, HIGH);
        lastBeep = now;
        beeping = true;
      }
      if (beeping && (now - lastBeep >= 100)) {
        digitalWrite(BUZZER_PIN, LOW);
        beeping = false;
        beepCount++;
      }
    }
  }

  // Ensure everything is off after feedback
  digitalWrite(BUZZER_PIN, LOW);
}

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Arduino Project

Arduino RFID Door Lock Project with MFRC522 V2

Course Introduction

Required Components

Wiring

Common Connections:

Writing the Code

Arduino Project

Arduino RFID Door Lock Project with MFRC522 V2

Course Introduction

Required Components

Wiring

Common Connections:

Writing the Code

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