IoT + Blockchain Sensor System

Decentralized Environmental Monitoring using ESP32, Flask & Ethereum (Sepolia)

This project demonstrates a tamper-proof IoT data logging system using:

• ESP32 + DHT22 temperature & humidity sensor
• Flask backend server
• SHA-256 hashing for data integrity
• Ethereum smart contract (Sepolia testnet) to store data hashes on-chain
• Real-time dashboard with charts & Etherscan verification

Sensor readings are stored locally AND on Ethereum blockchain, ensuring trust, transparency, and immutability.

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System Architecture

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Hardware Wiring (ESP32 → DHT22)

DHT22 Pin	ESP32 Pin
VCC (+)	3.3V
GND (-)	GND
DATA	GPIO 26

Note: DHT22 Data pin connected to GPIO26 (D26)

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Screenshots

Live IoT Dashboard

ESP32 + DHT22 Hardware Setup

Flask Server Logs (showing blockchain TX hash)

Ethereum Transaction Verified on Etherscan

ESP32 Serial Monitor Output

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Tech Stack

Layer	Technology
Hardware	ESP32 + DHT22
Comm	Wi-Fi HTTP
Backend	Flask (Python)
Database	SQLite
Blockchain	Solidity + Ethereum (Sepolia)
Web3	web3.py + Infura
Frontend	Bootstrap + Chart.js
Security	SHA-256 hashing

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Project Structure

iot-blockchain-sensor-system/
├── server.py # Flask API + Dashboard backend
├── blockchain_client.py # Ethereum Web3 client
├── firmware/ # ESP32 firmware
│ └── esp32_dht_client.ino # Arduino code for ESP32
├── templates/
│ └── dashboard.html # Frontend UI
├── static/
│ └── style.css # CSS styles for dashboard
├── smart_contract/ # Solidity contract + deployment notes
│ └── IoTDataLedger.sol
├── screenshots/ # Wiring, dashboard, and output screenshots
├── .gitignore # Prevents secret leakage
├── .env (not uploaded) # Environment variables (local only)
├── LICENSE # MIT License
└── README.md # Documentation

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Requirements

• Python 3.8+
• ESP32 board
• Arduino IDE
• MetaMask wallet
• Infura account (Sepolia RPC)

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Arduino Libraries Required

Install the following libraries in Arduino IDE using Library Manager:

• DHT sensor library by Adafruit
• Adafruit Unified Sensor
• WiFi (built-in for ESP32 boards)
• HTTPClient (built-in for ESP32 boards)

In Arduino IDE: Tools → Manage Libraries → Search & Install

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Setup Instructions

1. Clone repo

git clone https://github.com/ManjotSinghJolly/iot-blockchain-sensor-system
cd iot-blockchain-sensor-system

2. Virtual Environment

python -m venv venv
source venv/bin/activate   # Mac/Linux
venv\Scripts\activate      # Windows

3. Install Dependencies

pip install flask flask_sqlalchemy web3 python-dotenv

4. Create .env

SEPOLIA_RPC_URL=your_infura_url
PRIVATE_KEY=your_private_key
CONTRACT_ADDRESS=your_contract
ACCOUNT_ADDRESS=your_wallet_address

5. Run Backend

python server.py

Go to:

http://127.0.0.1:5000/dashboard

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How the System Works

Step	Action
1	ESP32 reads Temp & Humidity from DHT22
2	Sends readings via Wi-Fi → Flask API
3	Flask hashes data using SHA-256
4	Data stored locally in SQLite
5	Hash sent to Ethereum smart contract
6	Dashboard updates live with graphs + Etherscan link

Result: Sensor data becomes proven and verifiable.

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Features

Feature	Status
Real-time IoT sensor readings	✅
Local database storage	✅
SHA-256 data integrity	✅
Hash on Ethereum	✅
Etherscan verification buttons	✅
Live chart updates	✅
Pending vs confirmed TX display	✅

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Author

Manjot Singh Jolly

If you found this useful, consider ⭐ starring this repo!

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License

This project is licensed under the MIT License — see LICENSE file.