🚡 project presentation link

🖥️ presentation file

📄 project proposal file

🎥 demonstration video

Smart Metro Gate Access System Using ESP32

💡 Motivation

During the July 2024 student revolution in Bangladesh, many metro station gates were damaged due to failures in the centralized ticketing system, causing chaos and unrest. This project aims to develop a low-cost, reliable, and decentralized smart gate system that keeps functioning even when the internet or central servers are down. Our goal is to ensure smoother passenger flow, safer public transport, and robust operation during emergencies.

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❓ What This Project Is

The Smart Metro Gate Access System Using ESP32 is a decentralized, low-cost, and intelligent metro gate system designed to operate independently of the internet or central servers. It combines QR code tickets, RFID cards, and IR-based passenger detection to manage safe and efficient entry and exit at metro stations.

Key characteristics:

1. Dual-Access Authentication: Passengers can enter using either QR codes (scanned by ESP32-CAM) or RFID cards (read by PN532 modules).
2. Local Validation: Tickets are generated, stored, validated, and expired locally on an ESP32 server, ensuring the system works even when offline.
3. Automated Gate Control: A servo motor physically opens and closes the gate, triggered only when IR sensors detect a passenger.
4. Secure and Time-Limited Tickets: Each ticket is a unique, HMAC-SHA256 signed token with a 10-minute expiration to prevent misuse.
5. Modular, Scalable, and Robust: The system can be deployed at multiple gates, is easily expandable, and maintains operation during network or server failures.

In essence, this project is a smart, reliable, and self-contained metro gate solution that demonstrates how low-cost IoT devices can improve public transportation security, efficiency, and resilience.

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🚀 Project Overview

The Smart Metro Gate Access System Using ESP32 is a decentralized, dual-access metro entry system that operates independently of internet or centralized servers. It is designed to ensure uninterrupted passenger flow during both normal operations and network outages.

Unlike Dhaka Metro’s current setup — which relies heavily on centralized ticket servers and mechanical gates — this system uses multiple ESP32 microcontrollers to locally handle ticket generation, validation, and gate control within a self-contained Wi-Fi network.

The system consists of three main units:

1. ESP32 Server Unit (Main Controller):
   • Acts as a local Wi-Fi Access Point and database server.
   • Hosts a web-based ticket management interface where administrators can issue, view, and delete tickets.
   • Generates unique, time-limited tickets secured with HMAC-SHA256 encryption and displays them as QR codes on a TFT screen.
2. Gate Control Unit (ESP32-S3):
   • Connects to the server via the local Wi-Fi network.
   • Controls a servo motor that physically opens or closes the gate.
   • Uses two IR sensors to detect passenger presence and direction, ensuring safe gate operation.
3. ESP32-CAM & PN532 Reader Unit:
   • ESP32-CAM scans QR code tickets presented by passengers.
   • PN532 RFID module reads RFID cards for alternate access.
   • Both modules communicate with the server to validate user credentials.

All components communicate wirelessly within a local network, allowing the entire system to operate offline. Ticket validation, gate actuation, and expiration checks occur locally — ensuring robustness even when internet connectivity or central infrastructure fails.

In short, the system demonstrates how low-cost microcontrollers can be combined to create a resilient, intelligent, and secure metro gate solution suitable for modern urban transportation.

System Diagram

        ┌──────────────┐         Wi-Fi (Local AP)        ┌──────────────┐
        │   Server     │◄──────────────────────────────►│   Gate ESP32 │
        │ ESP32 (AP)   │                                 │   (Servo +   │
        │ - Ticket DB  │                                 │   IR + PN532)│
        │ - QR Display │                                 └──────────────┘
        │ - RFID Write │
        └──────┬───────┘
               │
               ▼
        ┌──────────────┐
        │ ESP32-CAM    │
        │ - QR Scan    │
        │ - Validate   │
        └──────────────┘

🧰 Features

• Passengers can enter using QR codes or RFID cards.
• Ticket validation happens locally, without internet dependency.
• Tickets expire after 10 minutes and are deleted automatically.
• Two IR sensors detect human presence for safe gate operation.
• Servo motor controls the gate barrier for smooth operation.

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🔩 Hardware Components

Component	Quantity	Role in Project
ESP32-S3 Dev Module	2	Controls servo, IR, and RFID; manages gate system logic
ESP32-CAM	1	Scans and validates QR code tickets
ESP32 Dev Module (Server)	1	Runs Wi-Fi AP, ticket database, GUI, and QR display
2.4 inch TFT Display (ILI9341)	1	Displays generated QR codes
PN532 RFID Module	2	Reads and writes RFID cards for passenger authentication
Servo Motor	2	Opens and closes the gate automatically (180° rotation, 90° each side)
IR Sensors	2	Detects passenger entry and exit; measures distance via infrared reflection
Soldering Lead & Wires	-	Connects all electronic components securely
PVC Board	1	Provides a stable structure for mounting hardware

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🔧 Project Setup

Software Requirements

• IDE: Arduino IDE (latest version recommended)
• Programming Language: C++
• Libraries Used:
  1. Adafruit NeoPixel by Adafruit
     • Controls single-wire-based LED pixels and strips like WS2812 NeoPixels.
  2. Adafruit PN532 by Adafruit
     • Provides SPI and I2C access to the PN532 RFID/Near Field Communication chip.
  3. ArduinoJson by Benoit Blanchon
     • A simple and efficient JSON library for embedded C++ on Arduino.
  4. ESP32Servo by Kevin Harrington, John K. Bennett
     • Allows ESP32 boards to control servo, tone, and analogWrite motors using Arduino semantics.
  5. Adafruit BusIO by Adafruit
     • Abstracts away I2C, SPI, and UART interfacing for easier communication.
  6. Adafruit DMA neopixel by Adafruit
     • DMA-based library for driving NeoPixels on SAMD21/SAMD51 microcontrollers (e.g., Feather M0/M4) without interrupting other tasks.
  7. Adafruit NeoPixel by Adafruit
     • Same as above, for controlling LED pixels and strips.

🛠️ Project Updates

1st Update: Ticket Generation

• Implemented a Wi-Fi-based ticketing system using ESP32.
• The ESP32 creates a local Wi-Fi network and hosts a web server where tickets can be issued and monitored.
• Each ticket:
  • Is a secure, random token signed with HMAC-SHA256
  • Has a 10-minute expiry
  • Can only be used once
• Tickets are stored in memory and old or used tickets are automatically cleaned up.
• The admin web page allows generating, viewing, and managing tickets through a simple interface.

2nd Update: Servo & IR Modules

• IR Modules: Send infrared light, detect reflection time, and calculate distance to determine passenger direction.
• Servo Motor: Rotates 180° (90° each side) to open/close the gate when a passenger is detected.

3rd Update: RFID Integration

• Set up an ESP32 with a PN532 RFID reader using I2C communication.
• The ESP32:
  • Initializes the PN532 reader and checks its firmware
  • Prepares to detect nearby RFID cards
• In the main loop:
  • Scans for RFID cards in real-time
  • Prints each card’s UID (unique ID) in hexadecimal format to the serial monitor
  • Waits 2 seconds before scanning again
• Essentially, the ESP32 functions as a real-time RFID card reader, enabling identification of authorized passengers at the gate.
• Hardware setup:
  • ESP32 module installed on gate side
  • Two IR modules for entry/exit detection
  • PN532 RFID reader (short range — card must be close to read)
  • PVC board for structural support

Received feedback — needs more modification.

Next (Final) Update

• ESP32-CAM scanning QR codes
• Display monitor showing QR codes
• Final soldering work

Notes:

• ESP32-CAM and display were low in stock, requiring in-person purchase.
• Assistance from a senior was needed for soldering due to limited equipment.

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⚙️ How It Works

The Smart Metro Gate Access System operates through a local Wi-Fi network managed by one ESP32 module acting as the main server. Other ESP32 devices (such as the gate controller and camera unit) connect to it to perform specific tasks. The system is designed to continue operating even when offline, making it reliable in emergencies or unstable network conditions.

🔹 Step 1: Ticket Creation and Management

• The main ESP32 server runs a local Wi-Fi Access Point (AP) and hosts a web-based ticket management interface.
• Passengers or administrators can connect to the ESP32’s Wi-Fi and generate tickets through this web page.
• Each ticket is:
  • A unique, randomly generated token signed with HMAC-SHA256 for security.
  • Stored temporarily in the ESP32’s memory.
  • Set to expire after 10 minutes to prevent misuse or sharing.
• The server also displays the generated ticket as a QR code on a TFT display for easy scanning.

🔹 Step 2: Passenger Detection

• Two IR sensors are installed near the gate to detect passenger presence and direction of movement.
• When a person approaches:
  • The first IR sensor detects entry.
  • The second IR sensor confirms movement through the gate.
• This dual-sensor setup helps the system differentiate between entry and exit and prevents false triggering.

🔹 Step 3: Ticket Verification

• Passengers can authenticate using either:
  • A QR code, scanned by the ESP32-CAM, or
  • An RFID card, read by the PN532 RFID module.
• Once scanned or tapped:
  • The corresponding ESP32 sends the ticket data (token or UID) to the main ESP32 server over the local Wi-Fi network.
  • The server checks whether the ticket or card is valid, unused, and unexpired in its local database.

🔹 Step 4: Gate Control

• If the validation is successful:
  • The main ESP32 sends a command to the gate ESP32 module, which controls a servo motor.
  • The servo rotates 90° to open the gate, allowing the passenger to pass.
  • After the IR sensors confirm passage, the servo returns to the closed position.
• Invalid or expired tickets trigger a denial signal, keeping the gate closed.

🔹 Step 5: Data Handling and Cleanup

• Each used ticket is immediately marked as used and removed from memory.
• A background process automatically deletes expired tickets to free up space and maintain security.
• The system requires no external storage or internet, keeping all validation local and secure.

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✅ Advantages

• 1. Offline Operation:

  Works without internet or centralized servers, ensuring continuous functionality during outages or emergencies.

• 2. Low-Cost Implementation:

  Uses affordable components like ESP32, PN532, and IR sensors — ideal for developing countries or small-scale transport systems.

• 3. Dual Access System:

  Supports both QR codes and RFID cards, offering flexibility for users and redundancy in case one system fails.

• 4. Local Ticket Validation:

  Reduces dependency on remote databases and prevents network delays or failures from affecting gate operation.

• 5. Security & Anti-Reuse:

  Each ticket is encrypted with HMAC-SHA256, expires after 10 minutes, and is automatically deleted after use.

• 6. Scalability:

  Can be easily expanded to support multiple gates within a local network or connected later to a central monitoring system.

• 7. Compact & Modular Design:

  The hardware is lightweight and portable, making it easy to demonstrate, test, or integrate into existing gate systems.

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⚠️ Disadvantages

• 1. Limited Range for RFID Reading:

  PN532 modules have short detection distances, requiring cards to be placed close to the reader.

• 2. No Central Database Synchronization (Yet):

  Since it’s locally operated, tickets or user data aren’t shared between gates unless manually configured.

• 3. Hardware Fragility:

  Breadboard or PVC-based setups can be prone to connection issues or instability during transport or extended use.

• 4. Limited Processing Power:

  ESP32 has restricted memory and CPU capacity, which may limit handling of high passenger volumes in large stations.

• 5. Manual Maintenance:

  Requires occasional reboots or resets to clear memory and ensure stable long-term performance.

• 6. Limited Visual Feedback:

  Small TFT displays may not provide enough visibility in bright outdoor conditions or for larger crowds.

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