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IoTIntermediateAges 18+An afternoon

Low-Cost Environmental Monitor for Indoor Spaces

Published May 26, 2026

This project enables anyone to build a practical environmental monitoring system for indoor spaces, providing real-time data on air quality and environmental conditions. It's useful for ensuring comfortable and healthy environments in places like a small office, a school classroom, or a hobby workshop. The output can help optimize ventilation or heating, potentially saving energy and improving well-being in an example application like a community center.

What you'll need

  • ESP32 development board x1
  • DHT11 temperature/humidity sensor x1
  • MQ-2 gas sensor (smoke/LPG/CH4) x1
  • Breadboard x1
  • Jumper wires (male-to-male) x10
  • Micro-USB cable x1
  • 5V power supply (e.g., phone charger) x1

Step-by-step

  1. 01

    Assemble Hardware Components

    Connect the DHT11 sensor: VCC to 3.3V on ESP32, GND to GND, and Data pin to ESP32 pin D2. For the MQ-2 sensor: VCC to 5V, GND to GND, and Analog Out (A0) to ESP32 pin A0 (GPIO36). Place components on the breadboard for stability and easy wiring.

  2. 02

    Install Development Environment and Libraries

    Install the Arduino IDE. Open 'Tools' -> 'Board' -> 'Boards Manager...' and search for 'ESP32' to install the ESP32 board definitions. Then, go to 'Sketch' -> 'Include Library' -> 'Manage Libraries...' and install 'DHT sensor library' by Adafruit and 'MQ2Unified'.

  3. 03

    Upload Initial Firmware

    Connect the ESP32 to your computer via micro-USB. Select the correct board ('ESP32 Dev Module') and port in the Arduino IDE 'Tools' menu. Upload a basic sketch that reads data from both sensors and prints it to the Serial Monitor (e.g., using `DHT.readTemperature()` and `MQ2.readRs()`). Verify readings are sensible.

  4. 04

    Implement Data Transmission

    Modify the sketch to connect to a local Wi-Fi network using `WiFi.begin("YOUR_SSID", "YOUR_PASSWORD")`. Then, implement a simple HTTP POST request using `HTTPClient` to send the sensor data to a local server or a simple data logging service every few seconds. Ensure your local server is running and configured to receive data.

  5. 05

    Set Up Data Visualization (Optional)

    On a computer on the same network, set up a simple web server (e.g., using Python Flask or Node.js Express) to receive the data. Create a basic HTML page with JavaScript to display the incoming temperature, humidity, and air quality readings dynamically. This provides a user-friendly interface for the environmental data.

Tips

  • For MQ-2 calibration, expose the sensor to fresh air for 24-48 hours before taking readings for better accuracy.
  • Consider adding a small OLED display directly to the ESP32 for on-device real-time readings without a separate server.
#esp32#environmental-monitoring#air-quality#dht11#mq2
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