Smart Door Lock with Fingerprint & RFID

Project Overview

This smart door lock combines two authentication methods for enhanced security: fingerprint biometrics and RFID cards. Users can unlock the door using either method, or require both for high-security areas.

Components Required

• Arduino Uno/Nano: Main microcontroller
• Optical Fingerprint Sensor (R307): Biometric authentication
• RC522 RFID Module: Card/tag reader
• 5V Solenoid Lock: Electromagnetic lock mechanism
• Relay Module: Control solenoid lock
• 16x2 LCD Display: User interface (I2C preferred)
• RFID Cards/Tags: For authentication
• Breadboard & Jumper Wires: For connections
• 5V Power Supply: For solenoid lock
• Push Button: For admin mode activation

Wiring Diagram

Connect all components to the Arduino:

Fingerprint Sensor (R307)

• VCC → 5V
• GND → GND
• Tx → Pin 2 (Software Serial Rx)
• Rx → Pin 3 (Software Serial Tx)

RC522 RFID Module

• 3.3V → 3.3V (Do NOT use 5V!)
• GND → GND
• RST → Pin 9
• SDA → Pin 10
• MOSI → Pin 11
• MISO → Pin 12
• SCK → Pin 13

Relay Module (Solenoid Lock)

• VCC → 5V
• GND → GND
• IN → Pin 7
• COM → 5V Power Supply
• NO → Solenoid Lock (+)

LCD Display (I2C)

• VCC → 5V
• GND → GND
• SDA → A4
• SCL → A5

Admin Button

• One leg → Pin 8
• Other leg → GND

Fingerprint Sensor Setup

First, enroll fingerprints using the Adafruit fingerprint library:

Install Libraries

// In Arduino IDE: Sketch → Include Library → Manage Libraries
// Search and install:
- Adafruit Fingerprint Sensor Library
- MFRC522 by GithubCommunity
- LiquidCrystal_I2C by Frank de Brabander

Enroll Fingerprints

Use the example sketch enroll from the Adafruit library:

File → Examples → Adafruit Fingerprint Sensor → enroll

// Upload and open Serial Monitor
// Follow prompts to place finger twice
// Note the ID number assigned (0, 1, 2, ...)

RFID Reader Setup

Read and store RFID card UIDs:

#include <MFRC522.h>
#include <SPI.h>

#define RST_PIN 9
#define SS_PIN 10

MFRC522 mfrc522(SS_PIN, RST_PIN);

void setup() {
  Serial.begin(9600);
  SPI.begin();
  mfrc522.PCD_Init();
  Serial.println("Scan RFID card to read UID...");
}

void loop() {
  if (mfrc522.PICC_IsNewCardPresent() && 
      mfrc522.PICC_ReadCardSerial()) {
    
    String uid = "";
    for (byte i = 0; i < mfrc522.uid.size; i++) {
      uid += String(mfrc522.uid.uidByte[i], HEX);
    }
    
    Serial.print("Card UID: ");
    Serial.println(uid);
    
    mfrc522.PICC_HaltA();
    mfrc522.PCD_StopCrypto1();
    delay(2000);
  }
}

Complete Arduino Code

Integrate both authentication methods:

#include <Adafruit_Fingerprint.h>
#include <MFRC522.h>
#include <LiquidCrystal_I2C.h>

// Pin definitions
#define FINGERPRINT_RX 2
#define FINGERPRINT_TX 3
#define RFID_RST 9
#define RFID_SS 10
#define RELAY_PIN 7
#define ADMIN_BUTTON 8

// Initialize components
SoftwareSerial fingerprintSerial(FINGERPRINT_RX, FINGERPRINT_TX);
Adafruit_Fingerprint fingerprint = Adafruit_Fingerprint(&fingerprintSerial);
MFRC522 mfrc522(RFID_SS, RFID_RST);
LiquidCrystal_I2C lcd(0x27, 16, 2);

// Authorized users (add your IDs here)
int authorizedFingerprints[] = {0, 1, 2};
String authorizedRFID[] = {"a1b2c3d4", "e5f6g7h8"};
int numFingerprints = 3;
int numRFID = 2;

void setup() {
  Serial.begin(9600);
  
  // Initialize fingerprint sensor
  fingerprint.begin(57600);
  if (fingerprint.verifyPassword()) {
    Serial.println("Fingerprint sensor found");
  }
  
  // Initialize RFID
  SPI.begin();
  mfrc522.PCD_Init();
  Serial.println("RFID reader initialized");
  
  // Initialize relay
  pinMode(RELAY_PIN, OUTPUT);
  digitalWrite(RELAY_PIN, HIGH); // Lock engaged
  
  // Initialize button
  pinMode(ADMIN_BUTTON, INPUT_PULLUP);
  
  // Initialize LCD
  lcd.init();
  lcd.backlight();
  lcd.setCursor(0, 0);
  lcd.print("Smart Door Lock");
  lcd.setCursor(0, 1);
  lcd.print("Ready...");
  
  delay(2000);
  lcd.clear();
}

void loop() {
  // Check for admin button
  if (digitalRead(ADMIN_BUTTON) == LOW) {
    adminMode();
    delay(500);
  }
  
  // Check fingerprint
  int fingerID = getFingerprintID();
  if (fingerID >= 0 && isFingerprintAuthorized(fingerID)) {
    unlockDoor("Fingerprint");
    logAccess("Fingerprint", fingerID);
    delay(5000);
  }
  
  // Check RFID
  String rfidUID = getRFID();
  if (rfidUID != "" && isRFIDAuthorized(rfidUID)) {
    unlockDoor("RFID");
    logAccess("RFID", rfidUID);
    delay(5000);
  }
  
  lcd.setCursor(0, 0);
  lcd.print("Waiting...     ");
  lcd.setCursor(0, 1);
  lcd.print("Scan or Touch  ");
}

int getFingerprintID() {
  uint8_t p = fingerprint.getImage();
  if (p != FINGERPRINT_OK) return -1;
  
  p = fingerprint.image2Tz();
  if (p != FINGERPRINT_OK) return -1;
  
  p = fingerprint.fingerFastSearch();
  if (p == FINGERPRINT_OK) {
    return fingerprint.fingerID;
  }
  return -1;
}

String getRFID() {
  if (mfrc522.PICC_IsNewCardPresent() && 
      mfrc522.PICC_ReadCardSerial()) {
    
    String uid = "";
    for (byte i = 0; i < mfrc522.uid.size; i++) {
      uid += String(mfrc522.uid.uidByte[i], HEX);
    }
    
    mfrc522.PICC_HaltA();
    mfrc522.PCD_StopCrypto1();
    return uid;
  }
  return "";
}

bool isFingerprintAuthorized(int id) {
  for (int i = 0; i < numFingerprints; i++) {
    if (authorizedFingerprints[i] == id) return true;
  }
  return false;
}

bool isRFIDAuthorized(String uid) {
  for (int i = 0; i < numRFID; i++) {
    if (authorizedRFID[i] == uid) return true;
  }
  return false;
}

void unlockDoor(String method) {
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Access Granted!");
  lcd.setCursor(0, 1);
  lcd.print(method);
  
  digitalWrite(RELAY_PIN, LOW); // Unlock
  
  Serial.print("UNLOCKED via ");
  Serial.println(method);
}

void logAccess(String method, int id) {
  Serial.print(millis());
  Serial.print(" - ");
  Serial.print(method);
  Serial.print(": ");
  Serial.println(id);
}

void adminMode() {
  lcd.clear();
  lcd.print("Admin Mode");
  Serial.println("Admin mode activated");
  // Add enrollment logic here
}

Security Considerations

Physical Security

• Use a secure enclosure for electronics
• Install backup power (battery)
• Add tamper detection switch
• Use security screws

Digital Security

• Store authorized IDs in EEPROM, not code
• Implement failed attempt limits
• Add timeout between attempts
• Log all access attempts
• Consider adding WiFi for remote alerts

Troubleshooting

Fingerprint Not Recognized

• Clean sensor surface
• Re-enroll fingerprints
• Check wiring (Tx/Rx swapped?)
• Verify power supply (5V stable)

RFID Not Reading

• Ensure 3.3V power (not 5V)
• Check SPI connections
• Move card closer to reader
• Remove metal objects nearby

Solenoid Not Activating

• Check separate power supply
• Verify relay connections
• Test relay with simple LED first
• Ensure common ground