🌤️ ESP8266 Weather Station

Weather monitoring system built with ESP8266 NodeMCU, featuring multiple sensors for temperature, humidity, atmospheric pressure, and air quality monitoring with real-time web interface.

📋 Features

• Multi-sensor monitoring: DHT11, BMP280, and MQ-135 sensors
• Real-time JSON data: Access sensor data via web browser
• Visual status indicators: LED-based system health monitoring
• WiFi connectivity: Static IP configuration with automatic reconnection
• Data validation: Sensor reading validation and error handling
• External weather data: Integration with WeatherAPI.com

🛠️ Hardware Components

Main Components

• ESP8266 NodeMCU - Main microcontroller
• DHT11 - Temperature and humidity sensor
• BMP280 - Barometric pressure and temperature sensor (I²C)
• MQ-135 - Air quality sensor
• 2x LEDs (Green & Red) - Status indicators
• 2x 220Ω Resistors - For LED current limiting
• 1x 10kΩ Resistor - DHT11 pull-up resistor
• Breadboard and jumper wires

🔌 Circuit Connections

DHT11 Sensor

DHT11          NodeMCU
VCC     →      3.3V (3V3 pin)
GND     →      GND
DATA    →      D5 (GPIO14)

Note: Connect 10kΩ resistor between VCC and DATA pins

BMP280 Sensor (I²C, Address: 0x76)

BMP280         NodeMCU
VIN     →      3.3V (3V3 pin)
GND     →      GND
SDA     →      D2 (GPIO4)
SCL     →      D1 (GPIO5)

MQ-135 Air Quality Sensor

MQ-135         NodeMCU
VCC     →      Vin (5V)
GND     →      GND
A0      →      A0 (ADC0 pin)

Note: D0 pin is not used in this project

Status LEDs

Green LED:
Anode (+)  →   D6 (GPIO12) through 220Ω resistor
Cathode(-) →   GND

Red LED:
Anode (+)  →   D7 (GPIO13) through 220Ω resistor
Cathode(-) →   GND

📊 LED Status Indicators

The system uses two LEDs to indicate operational status:

LED Pattern	Status	Description
🟢 Solid Green	All OK	All sensors working, WiFi connected
🟢 Slow Blink	Minor Issues	One sensor failure, system functional
🟢 Double Blink	WiFi Disconnected	Sensors OK, WiFi connection lost
🔴 Fast Blink	Multiple Failures	Multiple sensor failures
🔴 Solid Red	Critical Failure	System-wide failure

🚀 Installation & Setup

Prerequisites

• Arduino IDE with ESP8266 board package
• Required libraries (install via Library Manager):

  ESP8266WiFi
  ESP8266WebServer
  Adafruit_BMP280
  DHT sensor library
  ArduinoJson
  

Configuration

Warning

Arduino IDE File Structure Requirement

All .ino and .h files must be placed inside a folder named weather_station for Arduino IDE to compile properly. The main file weather_station.ino must have the same name as the containing folder. Failure to follow this structure will result in compilation errors.

Important

Configuration Setup

Before compiling, you must create your own config.h file from the example:

1. Copy config_example.h to config.h
2. Update your WiFi credentials, API key, and network settings
3. The config.h file is ignored by git to protect your sensitive information

1. Clone this repository

2. Copy config_example.h to config.h:

   cp config_example.h config.h

3. Open config.h and update your settings:

   // WiFi Configuration
   #define WIFI_SSID "Your_WiFi_Name"
   #define WIFI_PASSWORD "Your_WiFi_Password"
   
   // Static IP Configuration (optional)
   #define STATIC_IP IPAddress(192, 168, 1, 223)
   #define GATEWAY_IP IPAddress(192, 168, 1, 1)
   
   // API Security
   #define API_KEY "your_custom_api_key"
   
   // Weather API Configuration (optional)
   #define WEATHER_API_KEY "your_weather_api_key"
   #define WEATHER_API_LOCATION "YourCity"
   #define WEATHER_API_INTERVAL 300  // Seconds between API calls (300 = 5 minutes)
   
   // MQ135 Calibration (REQUIRED for accurate readings)
   #define MQ135_CLEAN_AIR_VALUE 200  // Update with your sensor's baseline

4. Weather API Setup (Optional): To enable weather data features, sign up for a free API key at WeatherAPI.com and update your config.h:

   • Replace "your_weather_api_key" with your actual API key
   • Replace "YourCity" with your desired location (e.g., "Guwahati", "London", "New York")
   • Adjust WEATHER_API_INTERVAL to control how often fresh data is fetched (300 seconds = 5 minutes)
   • If you don't configure this, the weather endpoints will return error messages

Caution

MQ135 Calibration Required

The MQ135 air quality sensor requires individual calibration as each sensor has different baseline values. You must update the MQ135_CLEAN_AIR_VALUE in your config.h file with your sensor's specific baseline reading. See the MQ135 Calibration section for detailed instructions.

Upload Process

1. Connect your NodeMCU to your computer
2. Select the correct board: Tools > Board > ESP8266 Boards > NodeMCU 1.0
3. Select the correct port: Tools > Port > [Your COM Port]
4. Upload the code: Sketch > Upload

🌐 Web Interface

Accessing the Weather Station

After successful connection, access your weather station at:

http://192.168.1.223/  (or your configured IP)

API Endpoints

Get Sensor Data (JSON)

GET /jsondata?key=your_api_key

Get Sensor Data with Weather (JSON)

GET /jsondata?key=your_api_key&weather=true

Sensor Data with Response:

Note

The weather field is included only when weather=true is requested.

{
  "sensors": {
    "temperature_dht": 30.3,
    "temperature_bmp": 29.6,
    "temperature_avg": 30,
    "humidity": 57.4,
    "pressure": 991.5,
    "air_quality_raw": 270,
    "air_quality_ppm": 554.0875,
    "air_quality_aqi": 63,
    "air_quality_status": "Moderate",
    "is_valid": true
  },
  "system": {
    "free_heap": 43368,
    "heap_fragmentation": 1,
    "max_free_block": 43264,
    "cpu_freq": 80,
    "uptime": 16,
    "uptime_formatted": "16s",
    "free_sketch_space": 1740800,
    "flash_chip_size": 4194304,
    "flash_chip_speed": 40
  },
  "wifi": {
    "ssid": "Mitra`s",
    "rssi": -30,
    "ip": "192.168.1.223",
    "mac": "8C:AA:B5:FB:FF:82"
  },
  "weather": {
    "location": "Guwahati, Assam",
    "temp_c": 27.2,
    "temp_f": 81,
    "condition": "Mist",
    "condition_icon": "//cdn.weatherapi.com/weather/64x64/night/143.png",
    "pressure_mb": 1004,
    "humidity": 89,
    "feelslike_c": 31.6,
    "uv": 0,
    "last_update": 16364,
    "is_valid": true,
    "airquality": {
      "co": 468.05,
      "no2": 3.515,
      "o3": 106,
      "so2": 2.96,
      "pm2_5": 20.35,
      "pm10": 20.905,
      "us_epa_index": 2,
      "gb_defra_index": 2
    },
    "seconds_since_update": 0,
    "can_fetch_new": false,
    "force_refreshed": false
  }
}

🔧 Customization

Sensor Reading Intervals

Modify timing in config.h:

#define SENSOR_READ_INTERVAL 5000  // 5 seconds
#define LED_UPDATE_INTERVAL 100    // LED update rate

Validation Ranges

Adjust sensor validation ranges:

#define TEMP_MIN -100.0
#define TEMP_MAX 100.0
#define PRESSURE_MIN 800.0
#define PRESSURE_MAX 1200.0

🌫 MQ135 Air Quality Sensor Calibration

The MQ135 sensor requires proper calibration for accurate air quality measurements. Each MQ135 sensor has unique characteristics and baseline values, making individual calibration essential.

Calibration Notes

Warning

Sensor Warm-up Required

MQ135 sensors require 24-48 hours of initial warm-up for stable readings. For best results, allow the sensor to run continuously for at least 24 hours before calibrating.

Tip

Calibration Tips

• Perform calibration in stable weather conditions
• Avoid calibrating during high humidity or temperature changes
• Take multiple readings and average them for better accuracy
• Re-calibrate if you move the sensor to a different environment

How Calibration Works

The calibration process determines the sensor's resistance in clean air (R0), which serves as a baseline for calculating gas concentrations:

1. Clean Air Reading: The sensor reads analog values in known clean air conditions
2. Resistance Calculation: Convert analog reading to resistance using the load resistor value
3. R0 Determination: Calculate baseline resistance using the clean air factor from the datasheet
4. PPM Calculation: Use the Rs/R0 ratio to determine gas concentration in parts per million

Calibration Parameters in config.h

You must modify these values in your config.h file based on your specific sensor:

// MQ-135 Calibration Configuration
#define MQ135_CLEAN_AIR_VALUE 200  // Your baseline reading in clean air
#define MQ135_RL_VALUE 1.0        // Load resistance (1kΩ in my case))
#define MQ135_RO_CLEAN_AIR_FACTOR 3.6  // From datasheet for 100ppm CO2
#define MQ135_CALIBRATION_SAMPLE_TIMES 50    // Number of samples for calibration
#define MQ135_CALIBRATION_SAMPLE_INTERVAL 500 // Time between samples (ms)

Setting Up Your MQ135 Calibration

Step 1: Find Your Clean Air Baseline

1. Place the sensor in clean outdoor air (away from pollution sources)
2. Power on the weather station and monitor the serial output
3. Look for the "MQ-135 Debug" section in serial monitor
4. Record the "Raw" analog reading after the sensor has warmed up (atleast 30 minutes)
5. This raw value becomes your MQ135_CLEAN_AIR_VALUE

Step 2: Verify Load Resistance

• Most MQ135 breakout boards use a 1kΩ or 10kΩ load resistor
• Check your board's schematic or documentation
• Update MQ135_RL_VALUE if different (value in kΩ)

Step 3: Adjust Clean Air Factor (Optional)

• MQ135_RO_CLEAN_AIR_FACTOR is typically 3.6 from the datasheet
• This represents the Rs/R0 ratio at 100ppm CO2 in clean air
• Usually doesn't need modification unless using a different reference gas

Step 4: Test and Validate

// Example calibration for different environments:

// Urban environment (slightly higher baseline):
#define MQ135_CLEAN_AIR_VALUE 250

// Rural/countryside (cleaner air):
#define MQ135_CLEAN_AIR_VALUE 180

// Indoor environment (after ventilation):
#define MQ135_CLEAN_AIR_VALUE 220

Understanding the Output

The sensor provides multiple air quality metrics:

• Raw Value: Direct analog reading (0-1024)
• Resistance: Calculated sensor resistance in kΩ
• PPM: Gas concentration in parts per million (CO2 equivalent)
• AQI: Air Quality Index (simplified scale 0-500)
• Status: Descriptive quality level (Good, Moderate, Unhealthy, etc.)

Accuracy Limitations

Note

This implementation provides a simplified air quality estimation:

• Real AQI considers multiple pollutants (PM2.5, PM10, O3, NO2, SO2, CO)
• MQ135 primarily responds to CO2, ammonia, and alcohol vapors
• Values are estimates suitable for general indoor air quality monitoring
• For precise measurements, use calibrated professional equipment

🐛 Troubleshooting

Common Issues

WiFi Connection Problems:

• Check SSID and password in config.h
• Verify network is 2.4GHz (ESP8266 doesn't support 5GHz)
• Check LED status patterns

Sensor Reading Issues:

• Verify wiring connections
• Check power supply (sensors need stable 3.3V/5V)
• Monitor serial output for error messages

Web Json Data Not Loading:

• Confirm IP address in serial monitor
• Check firewall settings
• Verify the device is on the same network

Serial Monitor Debug

Enable detailed debugging by monitoring serial output at 9600 baud rate.

🤝 Contributing

1. Fork the repository
2. Create a feature branch (git checkout -b feature/amazing-feature)
3. Commit your changes (git commit -m 'Add amazing feature')
4. Push to the branch (git push origin feature/amazing-feature)
5. Open a Pull Request

📋 TODO

• Properly configure AQI sensor calibration and thresholds
• Add weather forecast integration
• Mobile app development (almost done)

📄 License

This project is licensed under the MIT License - see the LICENSE file for details.

🙏 Acknowledgments

• Arduino community for extensive documentation
• Adafruit for excellent sensor libraries
• ESP8266 community for board support and examples
• Contributors to the open-source libraries used in this project

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Crafted with 💖 by Debojit

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