Simple Air Quality Monitor using data collected from the web (no local sensor).
Based on an ESP8266 and E-paper display.
This is not a general, multi-purpose code base, but a quick hack for personal use.
The air quality has been a real concern in the West from August 2020. Purple Air and Air Now maps are great tools to evaluate if you can dare point your nose outside the confine of your shelter or not. However, I wanted a solution that provides the current state of pollution in a glimpse, without relying logging on a computer.
Ideally, you would setup your own sensor and create your DIY display to monitor the pollution in real time. However, due to high demand, air quality sensors are out of stock everywhere!
The next best option is then to use the data already available. There are more than 15 Purple Air stations in a 500m diameter circle around my house, so it is possible to get data localized enough to be relevant. The next requirement for me was to create a low power solution: I would prefer to not contribute more to the global warming just for my personal convinience. So a typical solution relying on a Raspberry Pi single board computer is not considered here.
This project relies on micro-controller with WiFi capabilities to collect other people sensor data. The display is based on a E-Paper panel that does not consume current only when it needs to be updated. Since air quality is a slow evolving parameter, the board and panel are simply stopped between updates, leading to a very low power solution.
- Some notes on the design (historical data and power consumption)
- Hardware related info (pinout, etc.)
The STL models for the enclosure are in the ./stls directory.
The source Fusion-360 model is available with this link.
The enclosure holds the Huzzah in place without any screws.
Not by design, just un-unsed parts from previous projects:
- ESP8266 Adafruit Huzzah
- This was before I selected SAMD21 boards instead. Still, the ESP8266 seems a interesting solution for super low cost projects.
- 2.7in 3 colors E-paper Dislay
- I was initially attracted by the Black + Red capabilities of the panel, but refresh time was too slow (~20s) for ultra-low power projects like DigiBaro.
- LiPo battery.
The project is using PlatformIO. I develop using Visual Studio Code (https://code.visualstudio.com/docs) which play nicely with the PlatformIo extension.
Several of the unit test are also runnable on the native platform (Ubuntu 20.04
in my case). However, I configured the build to use a 32 bits architecture.
Since any modern computer will today be amd64, you will have to install the 32
bit compatibility packages:
sudo apt install gcc-multilib g++-multilib
Some dependencies are pulled using git submodules. Get them with:
git submodule init
git submodule update
cd lib # symlink to avoid building the full waveshare source tree
ln -s ../externals/ePaperDisplay/Arduino/epd2in7b epd2in7b
This includes the e-Paper driver from WaveShare and a fork of the great Adafruit GFX library.
Other "normal" dependencies are installed with PlatformIO:
- ArduinoJson + StreamUtils from bblanchon
You should set the wifi SSID and password in src/credentials.h.
This is also where you need to add your own PurpleAir API READ key.
Note: Purple Air now requires individual keys to access the sensor database. Check this post regarding the topic.