Arduino Project

Arduino RFID Door Lock Project with MFRC522 V11

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 11.0 access-control system using the I2C LCD, MFRC522 module, MQ-2 gas sensor, a digital servo motor, buzzer module, traffic light 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	Buzzer Modudle	1	BUY
6	MFRC522 Module	1	BUY
7	Power Supply Module	1	BUY
8	Digital Servo Motor	1	BUY
9	MQ-2 Gas Sensor Module	1	BUY
10	Traffic Light LED	1	BUY
11	I2C LCD 1602	1	BUY

Wiring

4.webp__PID:9d95c452-147e-4445-b56c-49087b514bcb

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.

Traffic light LED
R: Connect to 11 on the Arduino.
Y: Connect to 10 on the Arduino.
G: Connect to 9 on the Arduino.
GND: Connect to GND on the Arduino.

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 12 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 8 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.
To install the library, use the Arduino Library Manager and search for LiquidCrystal_I2C and install 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   // RFID UID length (4 bytes)

RFID1 rfid;
Servo myServo;
LiquidCrystal_I2C lcd(0x27, 16, 2);  // Change to 0x3F if the LCD stays blank

// Pin configuration
const int servoPin  = 8;     // Servo signal pin
const int buzzerPin = 12;    // Passive buzzer pin
const int smokePin  = A0;    // Smoke sensor analog output

// Traffic light pins
const int greenPin  = 9;
const int yellowPin = 10;
const int redPin    = 11;

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

// State flags
bool cardAction = false;             // True while the door is opening or closing
unsigned long cardTimer = 0;         // Used to keep the door open for a short time

bool smokeAlert = false;             // True when smoke level is above the threshold
bool smokeRecovering = false;        // Recovery period after smoke disappears
unsigned long smokeRecoverStart = 0; // Timer for recovery delay

int smokeValue = 0;                  // Current smoke sensor value
const int smokeThreshold = 200;      // Threshold that triggers the alarm

// Servo position control
int targetPos = 0;   // Target servo angle
int currentPos = 0;  // Current servo angle

// LCD page tracker
String lcdState = "";

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

// Move the servo gradually to the target position
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 confirmation beep for a valid card
void beepShort() {
  tone(buzzerPin, 2000);
  delay(80);
  noTone(buzzerPin);
}

// Warning sound for an invalid card
void beepDenied() {
  for (int i = 0; i < 4; i++) {
    tone(buzzerPin, 1600);
    delay(100);
    noTone(buzzerPin);
    delay(100);
  }
}

// Non-blocking alarm sound for smoke alert
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 the UID from the 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();   // Stop repeatedly reading the same card
  }
}

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

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

// Show the default waiting screen
void showNormal() {
  if (lcdState == "normal") return;

  lcdState = "normal";
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Door Locked");
  lcd.setCursor(0, 1);
  lcd.print("Scan Card");
}

// Show access granted message
void showAccessGranted() {
  if (lcdState == "grant") return;

  lcdState = "grant";
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Access Granted");
  lcd.setCursor(0, 1);
  lcd.print("Door Opening");
}

// Show fully open door message
void showDoorOpen() {
  if (lcdState == "open") return;

  lcdState = "open";
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Door Open");
  lcd.setCursor(0, 1);
  lcd.print("Enter Now");
}

// Show door closing message
void showDoorClosing() {
  if (lcdState == "closing") return;

  lcdState = "closing";
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Door Closing");
  lcd.setCursor(0, 1);
  lcd.print("Please Wait");
}

// Show invalid card message
void showAccessDenied() {
  if (lcdState == "denied") return;

  lcdState = "denied";
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Access Denied");
  lcd.setCursor(0, 1);
  lcd.print("Invalid Card");
}

// Show smoke warning message
void showSmokeWarning() {
  if (lcdState == "smoke") return;

  lcdState = "smoke";
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Smoke Alert");
  lcd.setCursor(0, 1);
  lcd.print("Evacuate Now");
}

// Set the traffic light LEDs
void setTrafficLight(bool r, bool y, bool g) {
  digitalWrite(redPin, r);
  digitalWrite(yellowPin, y);
  digitalWrite(greenPin, g);
}

// Update traffic lights based on the current state
void updateTrafficLight() {

  // Smoke alert has the highest priority
  // Red LED blinks faster during alarm
  if (smokeAlert || smokeRecovering) {
    static unsigned long lastBlink = 0;
    static bool redState = false;

    if (millis() - lastBlink > 150) {
      lastBlink = millis();
      redState = !redState;
    }

    digitalWrite(redPin, redState);
    digitalWrite(yellowPin, LOW);
    digitalWrite(greenPin, LOW);
    return;
  }

  // Yellow LED stays on while the door is moving
  if (currentPos != targetPos) {
    setTrafficLight(LOW, HIGH, LOW);
    return;
  }

  // Green LED stays on when the door is fully open
  if (currentPos >= 87 && targetPos == 90) {
    setTrafficLight(LOW, LOW, HIGH);
    return;
  }

  // Red LED stays on in the default locked state
  setTrafficLight(HIGH, LOW, LOW);
}

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

  pinMode(buzzerPin, OUTPUT);

  pinMode(redPin, OUTPUT);
  pinMode(yellowPin, OUTPUT);
  pinMode(greenPin, OUTPUT);

  // Initialize servo
  myServo.attach(servoPin);
  myServo.write(0);

  currentPos = 0;
  targetPos = 0;

  // Initialize LCD
  lcd.init();
  lcd.backlight();

  showNormal();
  updateTrafficLight();
}

// Main loop
void loop() {
  // Read smoke sensor value
  smokeValue = analogRead(smokePin);

  // Handle door movement after a valid card scan
  if (cardAction) {

    if (currentPos < 90 && targetPos == 90) {
      showAccessGranted();
      servoSmoothRun();
    }

    else if (currentPos >= 90 && targetPos == 90) {
      showDoorOpen();

      if (cardTimer == 0) cardTimer = millis();

      if (millis() - cardTimer >= 1500) {
        setServoAngle(0);
      }

      servoSmoothRun();
    }

    else if (targetPos == 0 && currentPos > 0) {
      showDoorClosing();
      servoSmoothRun();
    }
  }

  // Return to the normal page after the door is fully closed
  if (!smokeAlert && !smokeRecovering && currentPos <= 3 && targetPos == 0 && lcdState != "normal") {
    cardAction = false;
    cardTimer = 0;
    lcdState = "";
    showNormal();
  }

  // Smoke detection logic
  bool allowRFID = true;

  if (smokeValue > smokeThreshold) {
    smokeAlert = true;
    smokeRecovering = false;

    setServoAngle(90);
    beepAlarmNonBlock();
    showSmokeWarning();
    allowRFID = false;
  }
  else {
    if (smokeAlert) {

      if (!smokeRecovering) {
        smokeRecovering = true;
        smokeRecoverStart = millis();
      }

      if (millis() - smokeRecoverStart < 1500) {
        beepAlarmNonBlock();
        showSmokeWarning();
        allowRFID = false;
      }
      else {
        smokeAlert = false;
        smokeRecovering = false;

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

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

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

      if (idVerify()) {
        beepShort();
        showAccessGranted();

        setServoAngle(90);
        cardAction = true;
        cardTimer = 0;
      }
      else {
        showAccessDenied();
        beepDenied();
        delay(800);
        showNormal();
      }

      clearBuffer();
    }
  }

  // Keep the servo moving smoothly
  servoSmoothRun();

  // Update the traffic light every loop
  updateTrafficLight();
}

Recover password

Create my account

Arduino Project

Arduino RFID Door Lock Project with MFRC522 V11

Kit purchase

Course Introduction

Required Components

Wiring

Common Connections:

Writing the Code

Arduino Project

Arduino RFID Door Lock Project with MFRC522 V11

Kit purchase

Course Introduction

Required Components

Wiring

Common Connections:

Writing the Code

Subscribe to our newsletter