Arduino Project

Arduino RFID Door Lock Project with MFRC522 V6

Course Introduction

In this lesson, we’ll build a 6.0 access-control system using the MFRC522 module, a digital servo motor, buzzer module, and gas 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	MQ-2 Gas 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	I2C LCD 1602	1	BUY

Wiring

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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.

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.

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>
#include <LiquidCrystal_I2C.h>

#define ID_LEN 4    // Length of the RFID UID (4 bytes)

RFID1 rfid;
Servo myServo;
LiquidCrystal_I2C lcd(0x27, 16, 2);  // Change 0x27 → 0x3F if screen is blank


// ==== Pin Setup ====
const int servoPin  = 9;   // Servo signal pin
const int buzzerPin = 10;  // Passive buzzer pin
const int smokePin  = A0;  // Analog input from the smoke sensor


// ==== Authorized RFID Card UID (change to your own card) ====
uchar userId[ID_LEN] = {0x33, 0xF8, 0xB8, 0x1A};
uchar userIdRead[ID_LEN];   // Temporary buffer to store scanned UID


// ==== System State Flags ====
bool cardAction       = false;       // True while the door is opening/closing after valid card
unsigned long cardTimer = 0;         // Timer for keeping the door open

bool smokeAlert       = false;       // True when smoke level > threshold
bool smokeRecovering  = false;       // True when smoke just dropped below threshold, buffer period
unsigned long smokeRecoverStart = 0; // Timer for smoke recovery delay

int smokeValue = 0;                  // Current sensor reading
const int smokeThreshold = 200;      // Smoke alarm trigger threshold


// ==== Servo Control Values ====
int targetPos  = 0;  // Desired servo angle (0° or 90°)
int currentPos = 0;  // Incrementally updated servo position


// ==== LCD Page Lock ====
String lcdState = "";  // Stores the name of the current LCD page


// ======================= SERVO CONTROL =======================
void setServoAngle(int angle) {
  targetPos = constrain(angle, 0, 90);
}

void servoSmoothRun() {
  // Move the servo slowly, step-by-step (non-blocking)
  static unsigned long lastStep = 0;
  if (millis() - lastStep >= 15) {  // Move every 15 ms
    lastStep = millis();
    if (currentPos < targetPos) currentPos++;
    else if (currentPos > targetPos) currentPos--;
    myServo.write(currentPos);
  }
}


// ======================= BUZZER =======================
void beepShort() {
  tone(buzzerPin, 2000);
  delay(80);
  noTone(buzzerPin);
}

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

void beepAlarmNonBlock() {
  // Non-blocking beeping for smoke alarm
  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);
  }
}


// ======================= RFID =======================
void getId() {
  // Read 4 bytes UID into userIdRead[]
  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();   // Stop reading the same card repeatedly
  }
}

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

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


// ======================= LCD PAGES =======================
void showNormal() {
  lcdState = "normal";
  lcd.clear();
  lcd.setCursor(0, 0); lcd.print("Door: Locked");
  lcd.setCursor(0, 1); lcd.print("Please Tap Card");
}

void showAccessGranted() {
  lcdState = "grant";
  lcd.clear();
  lcd.setCursor(0, 0); lcd.print("Access Granted");
  lcd.setCursor(0, 1); lcd.print("Welcome!");
}

void showAccessDenied() {
  lcdState = "denied";
  lcd.clear();
  lcd.setCursor(0, 0); lcd.print("Access Denied");
  lcd.setCursor(0, 1); lcd.print("Try Again!");
}

void showSmokeWarning() {
  if (lcdState != "smoke") {
    lcdState = "smoke";
    lcd.clear();
    lcd.setCursor(0, 1); lcd.print("Run Away!!!");
  }
  lcd.setCursor(0, 0); lcd.print("Smoke: ");
  lcd.print(smokeValue);
  lcd.print("   "); // Clear leftover digits
}


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

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

  myServo.write(0);  // Start fully closed
  currentPos = 0;
  targetPos  = 0;

  lcd.init();
  lcd.backlight();
  showNormal();
}


// ======================= MAIN LOOP =======================
void loop() {

  smokeValue = analogRead(smokePin);  // Read smoke sensor value


  // ===== RFID Door Flow =====
  if (cardAction) {
    if (currentPos < 90) {          // Opening door
      servoSmoothRun();
    } else {                        // Door fully open → hold 1.5 seconds
      if (cardTimer == 0) cardTimer = millis();
      if (millis() - cardTimer >= 1500) {
        setServoAngle(0);           // Start closing
      }
      servoSmoothRun();
    }
  }


  // ===== After Servo Fully Closed → Clear State & Restore LCD =====
  if (!smokeAlert && currentPos <= 3 && targetPos == 0 && lcdState != "normal") {
    cardAction = false;     // FIX: allow second unlock!
    cardTimer  = 0;         // Reset timer
    lcdState   = "";        // Unlock LCD state
    showNormal();           // Main screen
  }


  // ===== Smoke Detection =====
  bool allowRFID = true;  // Disabled when smoke detected

  if (smokeValue > smokeThreshold) {
    smokeAlert      = true;
    smokeRecovering = false;
    setServoAngle(90);      // Safety: force door open
    beepAlarmNonBlock();
    showSmokeWarning();
    allowRFID = false;
  }
  else {
    if (smokeAlert) {
      // Smoke dropped → enter recovery buffer 1.5 seconds
      if (!smokeRecovering) {
        smokeRecovering = true;
        smokeRecoverStart = millis();
      }
      if (millis() - smokeRecoverStart < 1500) {
        beepAlarmNonBlock();
        showSmokeWarning();
        allowRFID = false;
      }
      else {
        // Smoke cleared → close door
        smokeAlert       = false;
        smokeRecovering  = false;
        setServoAngle(0);
        noTone(buzzerPin);
        allowRFID = true;
      }
    }
  }


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

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

      if (idVerify()) {            // Authorized card
        beepShort();
        showAccessGranted();
        setServoAngle(90);
        cardAction = true;
        cardTimer  = 0;
      }
      else {                       // Unauthorized card
        showAccessDenied();
        beepDenied();
        delay(800);
        showNormal();
      }
      clearBuffer();
    }
  }

  // Keep servo moving smoothly
  servoSmoothRun();
}

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Arduino Project

Arduino RFID Door Lock Project with MFRC522 V6

Course Introduction

Required Components

Wiring

Common Connections:

Writing the Code

Arduino Project

Arduino RFID Door Lock Project with MFRC522 V6

Course Introduction

Required Components

Wiring

Common Connections:

Writing the Code

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