Sentinel OS

The Aim

The primary aim of Sentinel OS is to bridge the gap between high-level security and human safety by integrating Two-Factor Authentication (2FA) with an automated emergency fail-safe. It seeks to eliminate the "death trap" risk of traditional electronic locks by utilizing thermal sensors to detect fire hazards and trigger an immediate, life-saving override of the locking mechanism.

Detailed Summary

Sentinel OS is a high-security, distributed embedded system designed to provide robust access control while prioritizing human safety during environmental emergencies. Built on a dual-node architecture, the system utilizes two Arduino Uno microcontrollers connected via an I2C communication bridge to separate user interface processing from real-time security monitoring.

This project earned a First Place Win in the Beginner Category.

Key Features & Functionality

Proximity-Activated Wake-up: An ultrasonic sensor detects approaching users within 50cm, transitioning the system from an idle "Armed" state to an active authentication mode.

Two-Factor Authentication (2FA): Access requires both a physical hardware token (RC522 RFID card/fob) and a secure 4-digit knowledge-based PIN entered via a 4x4 matrix keypad.

Persistent Data Memory: User PINs are stored in the microcontroller’s EEPROM, ensuring the security credentials remain saved even after a total power loss or system reset.

Interactive Dashboard: A 1.8-inch TFT LCD provides a real-time graphical interface, displaying system status, live temperature/humidity telemetry, and guided prompts for PIN entry and administrative resets.

Automated Fire Fail-Safe: Integrated with a DHT11 sensor, the system monitors for critical heat levels (≥34°C). Upon detection, it triggers an emergency override that instantly unlocks the door via the servo motor, flashes a red alert, and sounds a high-decibel siren to prevent entrapment.

Administrative Control: Authorized users can utilize a dedicated admin mode to verify current credentials and update the master PIN directly through the device interface.

Hardware Required

⚙️ 2x Arduino Uno Microcontrollers (Dual-node system)

📡 1x RFID RC522 Module

🔢 1x 4x4 Matrix Keypad (with custom key mapping)

1

2

3

A

4

5

6

B

7

8

9

C

Clear

0

Enter

D

📺 1x 1.8-inch TFT Screen Module

🦇 1x Ultrasonic Sensor

🌡️ 1x DHT11 Temperature & Humidity Sensor

⚙️ 1x Continuous Rotation Servo Motor

🔊 1x Active Buzzer

🚥 3x LEDs (Red, Yellow, Green)

The Final Product

The Team

Harshith R.S.

Lead Architect/p>

Zayaan H.

Hardware & Circuit Design

Divyansh A.

Circuit Design

Pranav M.V.

Hardware Design

Gemini 3.1 Pro

Lead Coder, C++ Logic (Carry)

Code Showcase: DHT11 Fail-Safe

The logic running on the internal node to ensure emergency fire unlock. (From Microcontroller 2)

  // 🚨 OVERHEAT ALARM & FAIL-SAFE UNLOCK
  else if (pendingCommand == 6) {
    Serial.println("Action: OVERHEAT! FAIL-SAFE UNLOCKING DOOR!");
    digitalWrite(YELLOW_LED, LOW);
    digitalWrite(RED_LED, HIGH);

    // 1. FORCE UNLOCK THE DOOR IMMEDIATELY
    lockServo.attach(SERVO_PIN);
    lockServo.write(180);
    delay(140);
    lockServo.write(90);
    lockServo.detach();

    // 2. PLAY SIREN WHILE DOOR IS OPEN (~4 seconds)
    for(int i = 0; i < 6; i++) {
      tone(BUZZER, 800, 300); delay(300);
      tone(BUZZER, 1200, 300); delay(300);
    }

    // 3. RELOCK THE DOOR (Once the alarm finishes)
    Serial.println("Action: SECURING DOOR AFTER ALARM");
    lockServo.attach(SERVO_PIN);
    lockServo.write(0);
    delay(140);
    lockServo.write(90);
    lockServo.detach();

    digitalWrite(RED_LED, LOW);
    pendingCommand = 0;
  }
          

A distributed, dual-node security hub that utilizes two-factor authentication and real-time environmental monitoring to provide secure, fail-safe access control.