Some time ago I had reason to log the quality of air in a room. We needed to know what the levels of carbon monoxide and carbon dioxide were at a given time. I quickly produced a thing on a strip of veroboard that would use an ESP8266 to log over WiFi to the ThingSpeak platform. This proved to be useful, and so I made a couple more on a PCB for various other locations.
The sensor uses a CCS811 (a low-power digital gas sensor) , BME280 (sensor measuring relative humidity, barometric pressure and ambient temperature) and DHT22 (capacitive humidity sensing digital temperature and humidity) sensors, with an OLED display and a small 5V 40mm fan to waft some air around prior to taking a reading. In reality the project no longer needs the DHT22 sensor, since the BME280 device provides better temperature and humidity measurements and adds air pressure readings. But it is included for historical reasons on my project. Feel free to omit it!
The project is very simple, as it just hooks up modules purchased from eBay. The modules cost less than £2 each at the time of writing and came from eBay or AliExpress.
Since this time, others have asked me for the design files, and so I have now shared them on GitHub: github.com/m1geo/ESP8266-Air-Quality-Sensor. The link contains everything you need to create your own! PCB files, source code and schematic.
If you follow the GitHub link above, you fill find two folders. These are explained in the subsequent sections below.
The code folder contains the Arduino code which runs on the ESP8266 device. You’ll need to source libraries for the SSD1306 OLED, the DHT22 (or cheaper DHT11), the Adafruit BME280 module, and the Adafruit CCS811 module. All these are available inside the Arduino IDE.
The MCU board used is a ESP8266 NodeMCU 1.0. This, and all the modules are easily sourced from the usual places (eBay, AliExpress, etc.), and are cheap. You’ll need to create a ThingSpeak account and then enter your API Key and channel number into the source code, as well as your WiFi name and passcode.
The board folder contains an example schematic design and basic PCB gerber files. You can use these gerber files to have a PCB made. All the cheap PCB houses will produce this board fine. The board files supplied are for the board shown above.
All files are on GitHub: github.com/m1geo/ESP8266-Air-Quality-Sensor