Arduino Fans

Here’s a complete outline and Arduino sketch for controlling a solenoid Gate lock using a fingerprint scanner, displaying status on a 0.91-inch I2C OLED (128×32 or 128×64), and storing/recognizing fingerprints.

🧰 Required Components

• Arduino Uno / Nano / Mega / ESP8266 / ESP32 (any)
• Fingerprint sensor (e.g., R307 or GT-521F52 or AS608)
• 12V Solenoid lock (with N-channel MOSFET like IRF540N or relay module)
• 0.91-inch I2C OLED (128×32 or 128×64) – SSD1306
• 12V power supply (for solenoid)
• Breadboard, jumper wires

🔌 Wiring Diagram (example)

Fingerprint Sensor (R307):

Uses SoftwareSerial for communication.

OLED (I2C SSD1306):

Solenoid Lock:

• Connect one side to 12V power
• Other side to drain of MOSFET
• MOSFET source to GND
• Gate controlled by Arduino digital pin via 220Ω resistor

📦 Libraries Required

• Adafruit_Fingerprint
• Adafruit_GFX
• Adafruit_SSD1306
• Wire

Install via Library Manager.

📇 How to Enroll Fingerprints

Run this example:
File → Examples → Adafruit Fingerprint Sensor Library → enroll

Upload and use the Serial Monitor to assign fingerprints to IDs (e.g., ID 1, 2, etc.)

🛡️ Notes

• Use a MOSFET or relay to switch the solenoid, not directly from Arduino.
• If using an ESP32, you can skip Software Serial and use a second hardware UART.

Here’s a step-by-step explanation of how the fingerprint-based solenoid lock system works:

🔄 System Workflow

1. Initialization

• When the system starts:
  • The OLED displays a welcome message ("Fingerprint Lock").
  • The fingerprint sensor is initialized and checked to ensure it’s working.
  • The solenoid pin is set to LOW, meaning the gate is locked by default.

2. Waiting for Finger

• The OLED displays: "Waiting for finger...".
• The system constantly waits for someone to place their finger on the scanner.

3. Fingerprint Scanning

• When a finger is placed:
  • The sensor captures the fingerprint image.
  • It converts the image to a template.
  • Then it compares the scanned template with the fingerprints stored in its internal memory.

4. Matching Fingerprint

• ✅ If a match is found:
  • The matched ID number is displayed on the OLED (e.g., "Welcome, ID #2").
  • The solenoid is activated by setting its control pin HIGH, which unlocks the gate.
  • OLED shows "Unlocking...".
  • After 1 seconds, the solenoid is turned off, locking the gate again.
• ❌ If no match is found:
  • OLED shows "Access Denied".
  • The system waits for a new fingerprint scan.

📇 Storing Fingerprints

• You must run the enroll example sketch (provided by the Adafruit Fingerprint library) once before using the system.
• That sketch lets you enroll new users by assigning each fingerprint a unique ID (e.g., ID 1, 2, 3…).
• These fingerprints are stored inside the fingerprint sensor module‘s memory (not the Arduino).

🔒 Solenoid Locking Mechanism

• A 12V solenoid lock is usually locked when unpowered and unlocked when powered.
• The Arduino controls it using a MOSFET or relay, which acts as a switch:
  • HIGH → unlock
  • LOW → lock

🖥️ OLED Display

• Shows current status:
  • "Waiting for finger..."
  • "Welcome, ID #..."
  • "Unlocking..."
  • "Access Denied"

🧠 Summary

✅ Arduino Code

#include <Adafruit_Fingerprint.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <Wire.h>
#include <SoftwareSerial.h>

// OLED config
#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 32 // Or 64, depending on your screen
#define OLED_RESET -1
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

// Fingerprint config
SoftwareSerial fingerSerial(2, 3); // RX, TX
Adafruit_Fingerprint finger = Adafruit_Fingerprint(&fingerSerial);

// Solenoid lock
#define SOLENOID_PIN 7

void setup() {
  pinMode(SOLENOID_PIN, OUTPUT);
  digitalWrite(SOLENOID_PIN, LOW); // Lock off

  Serial.begin(9600);
  finger.begin(57600);
  if (finger.verifyPassword()) {
    Serial.println("Found fingerprint sensor!");
  } else {
    Serial.println("Fingerprint sensor not found :(");
    while (1);
  }

  // OLED init
  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println("OLED not found");
    while (1);
  }
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
  display.setCursor(0,0);
  display.println("Fingerprint Lock");
  display.display();

  delay(2000);
}

void loop() {
  display.clearDisplay();
  display.setCursor(0,0);
  display.println("Waiting for finger...");
  display.display();

  getFingerprintID();
  delay(50);
}

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) {
    int id = finger.fingerID;
    Serial.print("Found ID #"); Serial.println(id);

    // Unlock gate
    display.clearDisplay();
    display.setCursor(0,0);
    display.print("Welcome, ID #");
    display.println(id);
    display.println("Unlocking...");
    display.display();

    digitalWrite(SOLENOID_PIN, HIGH);
    delay(1000); // Keep solenoid lock open for 1 sec
    digitalWrite(SOLENOID_PIN, LOW);
    return id;
  } else {
    display.clearDisplay();
    display.setCursor(0,0);
    display.println("Access Denied");
    display.display();
    delay(2000);
    return -1;
  }
}

✅ Conclusion: Arduino Fingerprint-Controlled Gate Lock

This project demonstrates a secure, efficient, and modern access control system using:

• Fingerprint recognition for authentication
• Arduino for core logic and control
• Relay or MOSFET for switching the 12V solenoid gate lock
• A compact I2C OLED display for live status feedback

🔐 Key Benefits:

• High security – only authorized fingerprints can unlock the gate
• User-friendly interface – OLED provides real-time feedback
• Expandable – add features like keypad override, Wi-Fi logging, or mobile alerts

🔧 Next Steps (Optional Enhancements):

• Admin menu to enroll/delete fingerprints via buttons or serial menu
• Add buzzer or LED indicators for sound/light feedback
• Implement battery backup or power fail safety
• Expand to multi-user or multi-door systems