🔥 Smart IoT Safety System: ESP32 & ESP8266 Gas & Water Leak Detector with MQTT

By Ilyass Oufaris

This project monitors gas and water leaks in real-time using ESP32 and ESP8266 boards with DHT11, MQ2, and water sensors. It communicates via MQTT and triggers alarms when leaks are detected. Perfect for learning IoT and MQTT communication.

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📌 System Overview

• ESP8266 — Kitchen Node: DHT11 + MQ2, sends data via MQTT
• ESP32 — Main Hub: DHT11 + MQ2 + Water Sensor + Buzzer, receives MQTT data
• Communication: MQTT using Mosquitto broker (kitchen_node/data topic)

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🛠 Hardware

• ESP8266 NodeMCU
• ESP32 Dev Module
• DHT11 x2
• MQ2 Gas Sensor x2
• Water Sensor
• Passive Buzzer
• Breadboard & jumper wires

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💻 Software

• Arduino IDE
• Libraries: PubSubClient, DHT sensor library, Adafruit Unified Sensor
• Mosquitto MQTT Broker (Windows)

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⚡ Quick Setup

1. Install Arduino IDE
2. Add ESP32 & ESP8266 boards in Preferences → Additional Boards Manager URLs:

[https://arduino.esp8266.com/stable/package_esp8266com_index.json](https://arduino.esp8266.com/stable/package_esp8266com_index.json),
[https://raw.githubusercontent.com/espressif/arduino-esp32/gh-pages/package_esp32_index.json](https://raw.githubusercontent.com/espressif/arduino-esp32/gh-pages/package_esp32_index.json)

3. Install the boards via Boards Manager
4. Install required libraries via Library Manager

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🔌 Wiring

ESP8266 (Kitchen Node): DHT11 → D2, MQ2 → A0, VCC → 3.3V, GND → GND
ESP32 (Main Hub): DHT11 → GPIO 4, MQ2 → GPIO 34, Water → GPIO 35, Buzzer → GPIO 18

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🚀 Mosquitto Setup

1. Install Mosquitto for Windows
2. Allow firewall access
3. Configure mosquitto.conf:

listener 1883
allow_anonymous true

4. Run CMD →

D:
cd Mosquitto
mosquitto.exe -c mosquitto.conf -v

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🖥 Testing

• Upload ESP8266_KitchenNode.ino to ESP8266, baud 9600
• Upload ESP32_MainHub.ino to ESP32, baud 115200
• Open Serial Monitors to see sensor data
• Buzzer triggers on gas/water leak detection

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⚠ Common Issues

• MQTT rc=-2 → Mosquitto not running or wrong IP
• DHT returns NaN → check wiring or sensor
• MQ2 max = 1023 on ESP8266 → normal 10-bit ADC

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🔐 Security

Do not upload real Wi-Fi credentials. Use placeholders.

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📌 License

MIT License – Free to use and modify

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🌍 Author

Ilyass Oufaris – IoT and embedded systems learning project