Arduino Project

Arduino RFID Door Lock Project with MFRC522 V9

Course Introduction

In this lesson, we’ll build a 9.0 access-control system using the MFRC522 module, MQ-2 gas sensor, a digital servo motor, buzzer module, 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	MFRC522 Module	1	BUY
7	Buzzer Modudle	1	BUY
8	Power Supply Module	1	BUY
9	Digital Servo Motor	1	BUY
10	MQ-2 Gas Sensor Module	1	BUY

Wiring

1.png__PID:e1154c9e-e500-4556-88a7-64be91014845

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.

MQ-2 Gas Sensor Module
A0: Connect to A0 on the Arduino.
GND: Connect to breadboard’s negative power bus.
VCC: Connect to breadboard’s red power bus.

Buzzer Module
I/0: Connect to 10 on the Arduino.
＋: Connect to breadboard’s red power bus.
－: 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.

Flame Sensor Module
D0: Connect to 11 on the Arduino.
GND: Connect to GND on the Arduino.
VCC: Connect to 5V 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   // RFID UID length

// Hardware pins
const int servoPin  = 9;    // Servo for door control
const int buzzerPin = 10;   // Buzzer for sound feedback
const int flamePin  = 11;   // Flame sensor (digital)
const int smokePin  = A0;   // Smoke sensor (analog)

// Objects
RFID1 rfid;
Servo myServo;

// Authorized RFID card UID
uchar userId[ID_LEN] = {0x33, 0xF8, 0xB8, 0x1A};
uchar userIdRead[ID_LEN];

// Servo position control (smooth movement)
int targetPos  = 0;
int currentPos = 0;

// Door action state (opened by RFID)
bool cardAction = false;
unsigned long cardTimer = 0;

// Emergency state (smoke or flame)
bool emergencyAlert = false;
bool emergencyRecovering = false;
unsigned long emergencyRecoverStart = 0;

// Smoke sensor threshold
int smokeValue = 0;
const int smokeThreshold = 200;

// Set the target angle for the servo
// The servo will move to this angle smoothly
void setServoAngle(int angle) {
  targetPos = constrain(angle, 0, 90);
}

// Move the servo step by step without blocking the program
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);
  }
}

// Short beep for access granted
void beepShort() {
  tone(buzzerPin, 2000);
  delay(80);
  noTone(buzzerPin);
}

// Beep pattern for access denied
void beepDenied() {
  for (int i = 0; i < 4; i++) {
    tone(buzzerPin, 1600);
    delay(100);
    noTone(buzzerPin);
    delay(100);
  }
}

// Continuous alarm sound without delay
void beepAlarmNonBlock() {
  static unsigned long t = 0;
  static bool buz = false;

  if (millis() - t > 120) {
    t = millis();
    buz = !buz;
    if (buz) tone(buzzerPin, 1500);
    else noTone(buzzerPin);
  }
}

// Read RFID card UID
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 the scanned card is authorized
bool idVerify() {
  for (int i = 0; i < ID_LEN; i++) {
    if (userIdRead[i] != userId[i]) return false;
  }
  return true;
}

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

void setup() {
  // Initialize RFID module (library-specific pins)
  rfid.begin(7, 5, 4, 3, 6, 2);
  rfid.init();

  pinMode(buzzerPin, OUTPUT);
  pinMode(flamePin, INPUT);

  // Initialize servo (door closed)
  myServo.attach(servoPin);
  myServo.write(0);
  currentPos = 0;
  targetPos  = 0;
}

void loop() {
  // Read sensors
  smokeValue = analogRead(smokePin);
  bool flameDetected = (digitalRead(flamePin) == LOW);

  bool emergencyDetected =
    (smokeValue > smokeThreshold) || flameDetected;

  bool allowRFID = true;

  // Emergency logic: force door open
  if (emergencyDetected) {
    emergencyAlert = true;
    emergencyRecovering = false;

    setServoAngle(90);
    beepAlarmNonBlock();
    allowRFID = false;
  }
  else {
    // Wait for emergency to fully clear before closing the door
    if (emergencyAlert) {
      if (!emergencyRecovering) {
        emergencyRecovering = true;
        emergencyRecoverStart = millis();
      }

      if (millis() - emergencyRecoverStart < 1500) {
        beepAlarmNonBlock();
        allowRFID = false;
      }
      else {
        emergencyAlert = false;
        emergencyRecovering = false;

        setServoAngle(0);
        noTone(buzzerPin);
        allowRFID = true;
      }
    }
  }

  // RFID access control
  if (allowRFID && !cardAction) {
    uchar status, str[MAX_LEN];
    status = rfid.request(PICC_REQIDL, str);

    if (status == MI_OK) {
      getId();

      if (idVerify()) {
        beepShort();
        setServoAngle(90);
        cardAction = true;
        cardTimer = 0;
      }
      else {
        beepDenied();
      }

      clearBuffer();
    }
  }

  // Auto close door after RFID access
  if (cardAction) {
    if (currentPos >= 90) {
      if (cardTimer == 0) cardTimer = millis();
      if (millis() - cardTimer >= 1500) {
        setServoAngle(0);
      }
    }

    if (currentPos <= 3 && targetPos == 0) {
      cardAction = false;
      cardTimer = 0;
    }
  }

  servoSmoothRun();
}

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Arduino Project

Arduino RFID Door Lock Project with MFRC522 V9

Course Introduction

Required Components

Wiring

Common Connections:

Writing the Code

Arduino Project

Arduino RFID Door Lock Project with MFRC522 V9

Course Introduction

Required Components

Wiring

Common Connections:

Writing the Code

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