Arduino Project

Arduino RFID Door Lock Project with MFRC522 V5

Kit purchase

Looking for parts? Check out our all-in-one kits below — packed with components, beginner-friendly guides, and tons of fun.

2.webp__PID:7d088a16-8752-49fb-8b1f-f9bba7297987

Name	Includes Arduino board	PURCHASE LINK
Elite Explorer Kit	Arduino Uno R4 WiFi	BUY
Inventor Lab Kit	Arduino Uno R3	BUY

Course Introduction

In this lesson, we’ll build a 5.0 access-control system using the MFRC522 module, active buzzer, a digital servo motor, and flame sensor module.

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	Flame Sensor Module	1	BUY
6	Active Buzzer	1	×
7	MFRC522 Module	1	BUY
8	Power Supply Module	1	BUY
9	Digital Servo Motor	1	BUY

Wiring

7.png__PID:4a7f9f00-c7a0-4701-a671-502effcb9695

Common Connections:

MFRC522 Module
IRQ: Connect to 7 on the Arduino.
SDA: Connect to 6 on the Arduino.
SCK: Connect to 5 on the Arduino.
MOSI: Connect to 4 on the Arduino.
MISO: Connect to 3 on the Arduino.
GND: Connect to breadboard’s negative power bus.
RST: Connect to 2 on the Arduino.
3.3V: Connect to breadboard’s passive power bus.

Flame Sensor Module
D0: Connect to 12 on the Arduino.
GND: Connect to breadboard’s negative power bus.
VCC: Connect to breadboard’s red power bus.

Active Buzzer
＋: Connect to 11 on the Arduino.
－: Connect to breadboard’s negative power bus.

Digital Servo Motor
Connect to breadboard’s positive power bus.
Connect to breadboard’s negative power bus.
Connect to 9 on the Arduino.

Writing the Code

Note
You can copy this code into Arduino IDE.
The RFID1 library is used here. You can click here RFID1.zip to download it.
Don’t forget to select the board(Arduino UNO R4 WIFI) and the correct port before clicking the Upload button.

  #include <rfid1.h>
#include <Servo.h>

#define ID_LEN 4

RFID1 rfid;
Servo myServo;

// Pin setup
const int servoPin  = 9;     // Servo motor pin
const int buzzerPin = 11;    // Active buzzer pin
const int flamePin  = 12;    // Flame sensor (LOW = fire detected)

// Your RFID card UID (you changed it)
uchar userId[ID_LEN] = {0x33, 0xF8, 0xB8, 0x1A};
uchar userIdRead[ID_LEN];

// State
bool cardAction       = false;
unsigned long cardTimer = 0;

bool flameAlert       = false;
bool flameRecovering  = false;
unsigned long flameRecoverStart = 0;

// Servo status
int targetPos  = 0;
int currentPos = 0;


// Set target servo angle (0–90)
void setServoAngle(int angle) {
  targetPos = constrain(angle, 0, 90);
}

// Move servo smoothly (non-blocking)
void servoSmoothRun() {
  static unsigned long lastStep = 0;
  if (millis() - lastStep >= 15) {
    lastStep = millis();
    if (currentPos < targetPos) currentPos++;
    else if (currentPos > targetPos) currentPos--;
    myServo.write(currentPos);
  }
}

// Beep without delay() (used for fire alarm)
void buzzerBeepNonBlock() {
  static unsigned long lastBeep = 0;
  static bool buzzState = false;
  if (millis() - lastBeep >= 120) {
    lastBeep = millis();
    buzzState = !buzzState;
    digitalWrite(buzzerPin, buzzState);
  }
}

// Read UID from RFID card
void getId() {
  uchar status, str[MAX_LEN];
  status = rfid.anticoll(str);
  if (status == MI_OK) {
    for (int i = 0; i < ID_LEN; i++) userIdRead[i] = str[i];
    rfid.halt();
  }
}

// Check if UID matches
bool idVerify() {
  for (int i = 0; i < ID_LEN; i++)
    if (userIdRead[i] != userId[i]) return false;
  return true;
}

// Clear UID buffer
void clearBuffer() {
  for (int i = 0; i < ID_LEN; i++) userIdRead[i] = 0;
}

// Faster beeps for invalid card (100ms)
void denyAccessBeep() {
  for (int i = 0; i < 4; i++) {
    digitalWrite(buzzerPin, HIGH); delay(100);
    digitalWrite(buzzerPin, LOW);  delay(100);
  }
  digitalWrite(buzzerPin, LOW);
}


// Setup runs once
void setup() {
  rfid.begin(7, 5, 4, 3, 6, 2);
  rfid.init();

  pinMode(buzzerPin, OUTPUT);
  pinMode(flamePin, INPUT);
  myServo.attach(servoPin);

  myServo.write(0);            // Door starts closed
  currentPos = 0;
  targetPos  = 0;
  digitalWrite(buzzerPin, LOW);
}


// Main loop
void loop() {

  // ------------ Valid card → open → hold → close ------------
  if (cardAction) {

    // Keep opening until fully open
    if (currentPos < 90) {
      servoSmoothRun();
      return;
    }

    // Start hold timer (1.5s) after fully opened
    if (cardTimer == 0) {
      cardTimer = millis();
    }

    // 1.5s hold time reached → close door
    if (millis() - cardTimer >= 1500) {
      setServoAngle(0);
      cardAction = false;
      cardTimer  = 0;
      digitalWrite(buzzerPin, LOW);
    }

    servoSmoothRun();
    return;
  }


  // ------------ Flame detection & alarm ------------
  bool flameDetected = (digitalRead(flamePin) == LOW);
  bool allowRFID = false;

  if (flameDetected) {
    flameAlert       = true;
    flameRecovering  = false;
    setServoAngle(90);         // Open immediately
    buzzerBeepNonBlock();      // Alarm (non-blocking)
    allowRFID = false;
  }
  else {
    if (flameAlert) {          // Fire just stopped
      if (!flameRecovering) {
        flameRecovering = true;
        flameRecoverStart = millis();
      }

      // Keep alarm 1.5s more after fire stops
      if (millis() - flameRecoverStart < 1500) {
        buzzerBeepNonBlock();
        allowRFID = false;
      } else {
        flameAlert       = false;
        flameRecovering  = false;
        setServoAngle(0);     // Close door
        digitalWrite(buzzerPin, LOW);
        allowRFID = true;
      }
    } else {
      digitalWrite(buzzerPin, LOW);
      allowRFID = true;
    }
  }

  // ------------ RFID scanning if allowed ------------
  if (allowRFID) {
    uchar status, str[MAX_LEN];
    status = rfid.request(PICC_REQIDL, str);
    if (status == MI_OK) {
      getId();
      if (idVerify()) {

        // 🔔 Short beep feedback when opening door
        digitalWrite(buzzerPin, HIGH); delay(80);
        digitalWrite(buzzerPin, LOW);

        setServoAngle(90);
        cardAction = true;
        cardTimer  = 0;
      } else {
        denyAccessBeep();
      }
      clearBuffer();
    }
  }

  // Keep servo smooth always
  servoSmoothRun();
}

Recover password

Create my account

Arduino Project

Arduino RFID Door Lock Project with MFRC522 V5

Kit purchase

Course Introduction

Required Components

Wiring

Common Connections:

Writing the Code

Arduino Project

Arduino RFID Door Lock Project with MFRC522 V5

Kit purchase

Course Introduction

Required Components

Wiring

Common Connections:

Writing the Code

Subscribe to our newsletter