Raspberry Pi Air Quality Monitor

Full-stack local IOT air quality monitor that runs on a Raspberry Pi.

Consists of

• cron job Python script for reading data
• SQLite database for storing data
• Go chi API for retrieving stored data and creating current readings
• Preact client for displaying readings

AQI Conversion Note

Conversion to equivalent AQI is performed using the formulas found in this document from airnow.gov.
Note that this is not actual AQI, as an actual AQI calculation uses measurements over a 24-hour period and requires data about pollutants other than PM2.5 such as PM10, Ozone, CO, NO2, and SO2.

Screenshots of Web Interface

Live Readings (updates every 5s)

Recent Readings Table

Equivalent AQI Graph

PM 1.0 and 2.5 Graph

Required materials

• Plantower PM2.5 Air Quality Sensor
• Raspberry Pi (Only tested with the Pi Zero W, but any model after the Pi 1 Model B should work--no guarantees though)

Setup Instructions

These instructions assume the device is running Raspberry Pi OS (previously called Raspbian). A full-featured guide to installing Raspberry Pi OS can be found here

Set Up Hardware

Connect the detector to the Raspberry Pi using the Pi diagram on this page.
Then enable serial output by following these instructions on how to use raspi-config

Clone the Repository

Install Git on the Raspberry Pi.
Then cd /home/pi and git clone https://github.com/gmelsby/air-detector.git
Further instructions only work if the repo is cloned into /home/pi

Setup Sqlite Database

Install sqlite3 on your device
Then cd /home/pi/air-detector
Run cat schema.sql | sqlite3 quality.db to create the database

Create Venv and Install Dependencies for Python Detector Program

Move into the pm2_5 directory with cd /home/pi/air-detector/pm2_5
Create virtual environment with python3 -m venv .venv
Activate virtual environment with source .venv/bin/activate
Install necessary dependencies with pip install -r requirements.txt
Test that setup has been successful so far with python3 detector.py -sv
If your setup has been successful, you should see output in this format:

reading from sensor
writing values to database
successfully wrote to database
{"pm1": 1, "pm25": 2, "pm1env": 1, "pm25env": 2, "particles03": 504, "particles05": 126, "localTime": "2023-08-01 14:34:11"}

This confirms that our dependencies have installed correctly and we can read from the sensor and write to the SQLite database.
Deactivate the virtual environment with deactivate

Create Cron Job to read and store data at a constant interval

Run crontab -e
In the editor, insert the following at the bottom of the file:

*/10 * * * * /home/pi/air-detector/pm2_5/.venv/bin/python /home/pi/air-detector/pm2_5/detector.py -s

Save and exit the editor.

Build and Host API

Install Go by following these instructions. The release to install will have armv6l in the file name--you can find a list of releases here.
Pick the most recent release in the form go.x.y.z.linux-armv6l.tar.gz.
Move to the API directory with cd /home/pi/air-detector/webapp/api
Install dependencies with go mod tidy
Make a directory to store built executable with mkdir build
Build the executable by running go build -o build
Create a systemd service to automatically run the API server by symlinking airwebappapi.service with sudo ls -s /home/pi/air-detector/webapp/api/airwebappapi.service /etc/systemd/system/airwebappapi.service
Reload the systemd services with sudo systemctl daemon-reload
The API should now be accessible on port 3000 of the device.

Build Preact App

Install the latest supported version of node on the Pi.
For the Pi Zero and Pi Zero W, an unofficial build of Node from nodejs.org is the best option.
Navigate to the root of the client app with cd /home/pi/air-detector/webapp/client
Install dependencies with npm i. This may take a while depending on which Raspberry Pi model you have.
Build the client with npm run build
The built static app should now be in the dist folder.

Host Client and API with Nginx

Install Nginx with apt
Modify /etc/nginx/nginx.conf by inserting

server {
		listen 0.0.0.0:80;
		location / {
			root /home/pi/air-detector/webapp/client/dist;
			try_files $uri $uri/ /index.html;
		}
		location /api/ {
			proxy_pass http://127.0.0.1:3000/;
		}
	}

in the http block.
Refresh Nginx with sudo nginx -s reload
The client app should now be available at [your pi's hostname].local or [your pi's IP address] on your local network.
The API should now be available at [your pi's hostname].local/api or [your pi's IP address]/api.