RFID Access9.0

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Kit purchase

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

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 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.

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	Buzzer Modudle	1	BUY
7	MFRC522 Module	1	BUY
8	Power Supply Module	1	BUY
9	Digital Servo Motor	1	BUY
10	MQ-2 Gas Sensor Module	1	BUY

Wiring

Common Connections:

MFRC522 Module
- IRQ: Connect to 7 on the ESP32.
- SDA: Connect to 6 on the ESP32.
- SCK: Connect to 5 on the ESP32.
- MOSI: Connect to 4 on the ESP32.
- MISO: Connect to 3 on the ESP32.
- GND: Connect to breadboard’s negative power bus.
- RST: Connect to 2 on the ESP32.
- 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();
}