Air Quality Monitoring System

This project is an air quality monitoring system running on a Raspberry Pi. It reads sensor data from two devices:

• PMSA003 Sensor: Measures particulate matter (PM) concentrations (e.g., PM2.5, PM10, etc.) using hardware I2C.
• SGP40 Sensor: Measures VOC (volatile organic compounds) levels using software I2C (BitBangI2C).

The system is built using FastAPI to handle sensor data aggregation and Streamlit to display the data in a web dashboard.

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How It Works

1. FastAPI Server (fastapi_server.py):

   • The server defines a /data endpoint.
   • It calls two functions from sensors.py:
     • read_pmsa003_i2c(): Reads air quality data from the PMSA003 sensor.
     • read_sgp40_i2c(): Retrieves the VOC measurement from the SGP40 sensor (which internally calls read_sgp40_sw()).
   • Results from both sensors are combined into a JSON response with keys pmsa0031 and sgp40.

2. Sensor Code (sensors.py):

   • PMSA003 Sensor:
     • Uses the hardware I2C interface from the busio module and the adafruit_pm25 library.
   • SGP40 Sensor:
     • Uses a software I2C bus created with adafruit_bitbangio.
     • The read_sgp40_sw() function reads raw VOC values using the adafruit_sgp40 library.
     • The read_sgp40_i2c() function wraps the raw VOC value in a dictionary before it is sent to the API.

3. Streamlit Apps:

   • Local Version (streamlit_app.py):
     • Continuously polls the FastAPI endpoint to display live sensor readings.
   • Cloud Version (cloud/streamlit_app.py):
     • Uses a public ngrok endpoint to access the API.
     • Additionally, it leverages helper functions (e.g., interpret_air_quality() and display_particle_counts()) to format the PMSA003 sensor data.

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Setup and Deployment

1. SSH into the Raspberry Pi:

   ssh airquality@airquality.local
   (Password: wifi hint)
   

2. Activate the Virtual Environment:

   source venv/bin/activate
   

3. Running the FastAPI Server:
   On the Raspberry Pi, start the FastAPI server using uvicorn:

   uvicorn fastapi_server:app --host 0.0.0.0 --port=8000 --reload
   

4. Expose the API via ngrok:
   On the Raspberry Pi, run:

   ngrok http --hostname=whale-pro-marmot.ngrok-free.app 8000
   

5. Running the Streamlit App:
   From a local machine or cloud server, launch the app:

   • Local version:

     streamlit run streamlit_app.py --server.enableCORS false --server.enableXsrfProtection false
     

   • Cloud version (if using the ngrok endpoint):

     streamlit run cloud/streamlit_app.py --server.enableCORS false --server.enableXsrfProtection false
     

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Libraries and Tools

• FastAPI: Fast, asynchronous web framework for building APIs.
• Uvicorn: ASGI server used to run the FastAPI application.
• Streamlit: Framework for creating interactive dashboards and web apps.
• adafruit_pm25: Library to interface with the PMSA003 air quality sensor.
• adafruit_sgp40: Library to interface with the SGP40 VOC sensor.
• busio: For hardware I2C communication.
• bitbangio: For creating a software I2C bus when hardware I2C is not available or for alternate configurations.
• ngrok: Tool for exposing local servers to the public internet.

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Notes

• Ensure your sensors are connected to the correct GPIO pins on your Raspberry Pi.
• After making changes to the code (especially in sensors.py), restart the FastAPI server so that updates are applied.
• The Streamlit apps continuously query the API endpoint, so modify the refresh interval (currently 5 seconds) as necessary for your setup.

Happy Monitoring!