Arduino Fingerprint Based Door Lock System

 1. Introduction

Security systems are essential in homes, offices, and laboratories. Traditional locks can be duplicated or broken, but biometric systems provide a higher level of protection.

In this project, we design a Fingerprint Based Door Lock System using Arduino, where only authorized users can unlock the door using their fingerprint.

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2. Components

• Arduino Nano / Uno
• Fingerprint Sensor (R307 / R305)
• Relay Module
• Solenoid Door Lock
• Jumper Wires
• Power Supply

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3. Circuit and Connections

• Fingerprint Sensor TX → Arduino D2
• Fingerprint Sensor RX → Arduino D3
• Relay Input → Arduino D8
• VCC → 5V
• GND → GND
• Relay Normally Closed → 12V Power Supply Positive ( choose Power Supply to the ampere of Solenoid Lock)
• Relay Common  → Solenoid Lock Positive
• Solenoid Lock Negative → 12V Power Supply Ground

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4. Circuit Working

The fingerprint sensor scans the user's finger and converts it into a digital template.

• If fingerprint matches stored data → Arduino activates relay → Door unlocks
• If fingerprint does not match → Access denied
• After a few seconds → Door locks automatically

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5. Code

#include <Adafruit_Fingerprint.h>
#include <SoftwareSerial.h>

SoftwareSerial mySerial(2, 3);
Adafruit_Fingerprint finger = Adafruit_Fingerprint(&mySerial);

int relayPin = 8;

void setup() {
  pinMode(relayPin, OUTPUT);
  digitalWrite(relayPin, LOW);

  Serial.begin(9600);
  finger.begin(57600);

  if (finger.verifyPassword()) {
    Serial.println("Sensor found");
  } else {
    Serial.println("Sensor not found");
    while (1);
  }
}

void loop() {
  int id = getFingerprintID();

  if (id > 0) {
    digitalWrite(relayPin, HIGH);
    delay(5000);
    digitalWrite(relayPin, LOW);
  }
}

int getFingerprintID() {
  uint8_t p = finger.getImage();
  if (p != FINGERPRINT_OK) return -1;

  p = finger.image2Tz();
  if (p != FINGERPRINT_OK) return -1;

  p = finger.fingerFastSearch();
  if (p != FINGERPRINT_OK) return -1;

  return finger.fingerID;
}

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6. Code Working

• Arduino communicates with fingerprint sensor using serial communication
• Sensor checks for fingerprint input
• If match is found → returns ID
• Arduino activates relay → Unlocks door
• After delay → Relay OFF → Door locks

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7. Tips

• Enroll fingerprints before running system
• Use external power for solenoid lock
• Ensure TX and RX are correctly connected
• Keep sensor clean for accurate detection

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8. Uses

• Home security systems
• Office access control
• Biometric attendance
• Secure lockers

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9. Conclusion

This Arduino Fingerprint Door Lock System is a reliable and secure solution for access control. It is easy to build and highly useful in real-world applications.

10. Arduino Fingerprint Enrollment Code (R307)

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Step 1: Install Required Library

Open Arduino IDE:

• Go to Sketch → Include Library → Manage Libraries
• Search and install: Adafruit Fingerprint Sensor Library

💻 Enrollment Code

#include <Adafruit_Fingerprint.h>
#include <SoftwareSerial.h>

SoftwareSerial mySerial(2, 3);
Adafruit_Fingerprint finger = Adafruit_Fingerprint(&mySerial);

int id;

void setup() {
  Serial.begin(9600);
  while (!Serial);  

  Serial.println("Fingerprint Enrollment");

  finger.begin(57600);

  if (finger.verifyPassword()) {
    Serial.println("Sensor detected!");
  } else {
    Serial.println("Sensor not found");
    while (1);
  }
}

void loop() {
  Serial.println("Enter ID (1 to 127): ");
  while (Serial.available() == 0);
  id = Serial.parseInt();

  if (id == 0) {
    Serial.println("Invalid ID");
    return;
  }

  Serial.print("Enrolling ID #");
  Serial.println(id);

  enrollFingerprint(id);
}

void enrollFingerprint(int id) {
  int p = -1;

  Serial.println("Place finger on sensor");
  while (p != FINGERPRINT_OK) {
    p = finger.getImage();
  }

  p = finger.image2Tz(1);
  if (p != FINGERPRINT_OK) {
    Serial.println("Error converting image");
    return;
  }

  Serial.println("Remove finger");
  delay(2000);
  while (finger.getImage() != FINGERPRINT_NOFINGER);

  Serial.println("Place same finger again");
  p = -1;
  while (p != FINGERPRINT_OK) {
    p = finger.getImage();
  }

  p = finger.image2Tz(2);
  if (p != FINGERPRINT_OK) {
    Serial.println("Error converting image");
    return;
  }

  p = finger.createModel();
  if (p != FINGERPRINT_OK) {
    Serial.println("Error creating model");
    return;
  }

  p = finger.storeModel(id);
  if (p == FINGERPRINT_OK) {
    Serial.println("Fingerprint Stored Successfully!");
  } else {
    Serial.println("Error storing fingerprint");
  }
}

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▶️ How to Use

Step 1. Upload code
Step 2. Open Serial Monitor (set 9600 baud)
Step 3. You will see message like:

             Ready to enroll a fingerprint!
            

Step 4. Enter ID (like 1, 2, 3, 4, …127)

           Type a number (example: 1) and press Enter

This ID is used to identify the person later.

1. Follow instructions:

   1. Place finger on sensor
   2. Remove finger
   3. Place same finger again

   You will see:

   Image taken
   Image converted
   Stored!

   Step 5. Done

             Now your fingerprint is stored in sensor memory 

🔍 Important Tips

• Use same finger twice properly
• Keep finger clean
• Don’t move finger while scanning
• You can store multiple users (ID 1, 2, 3,…127)
• Don’t use ID 0
• Max IDs ≈ 127 fingerprints
• If error → clean sensor & retry
• Use stable power (very important ⚠️)

Now you can load the original code and the stored finger will unlock the solenoid valve or servo motor