The CO2 Dice

The CO2 Dice is a high quality CO2 Sensor for rooms with a very simple display in the form of a dice.
It's software and hardware Open-Source

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The CO2 Dice has a very simple implementation with multiple build options and future expandability in soft- and hardware.
And it's built to be cheap and easy to assemble.

There are multiple scientific studies that link the levels of CO2 in the air to the spread rate of coronavirus. Simply put the more times air goes through a different set of lungs, the likelier an infection with a virus, given there's an infected person the same room. Ventilation, and fresh air management (by opening windows) can keep these levels down.
Also: the prolonged stay in a CO2 rich environment can cause fatigue, nausea, headaches and worse. So fresh air, and a device that tells you when to go get it is a good idea in general.

This project is aimed at producing a simple and cheap, yet capable device that is easy to build and roll out in large numbers. There are still a lot of resources free in the micro-controller, so it is easy to extend and modify.

Required parts

The following parts are required to build the CO2-Dice:

  • A WeMos 8266 D1 mini board
  • A Sensirion SCD30 CO2 Sensor board
  • 9 WS2818B LEDs (part of a strip works fine)  OR one of the assembled CO2-Dice PCB boards.


The circuit diagram and PCB layout can be found here:  
The software and additional resources are available here:

The hardware and software parts are licensed under the 'GNU GENERAL PUBLIC LICENSE Version 3'

  • HD version in testing

    Dirk Herrendoerfer04/29/2021 at 09:17 0 comments

    April 2021 Update:

    The kids working with this have declared the 3 by 3 matrix display as 'boring'.

    So I've had a couple of HD versions built that now have a 5 by 5 LED matrix. Also the new version now has an extra RTC and a barometric pressure sensor. 

    Let's see what they think of it.

  • Project updates

    Dirk Herrendoerfer11/12/2020 at 10:28 0 comments

    There have been a few updates to the Project:

    October 2020: 

    The Dice has been tested in a classroom environment with very positive results. The limits set did work with the large classroom and about 25 students, the CO2 levels rose until the Dice signalled a 'fresh air required' situation. Windows were opened for 5 minutes and the CO2 Level dropped to acceptable levels.  A small classroom with a working group of 10 never reached unacceptable levels, as it had a ventilation system. Still the Dice did signal elevated levels, and the room was aired out, and subsequently ok to use. Both the desk stand and wall mount were tested. Both worked fine showing the same CO2 levels.

    A code update was posted, and missing files were added to the git repo.

    November 2020: 

    Several tests were conducted to verify that the dice itself generates enough flow of air around the dice. Oddly, the documentation from the sensor supplier is only available as a draft ( funny!) document. It was verified that the sensor does indeed get a very good sniff of the air. There will be no closed housings for the dice, as this might impact the air flow.

    A test was performed using the WiFi capabilities of the micro-controller to verify that the signal does not interfere with the sensor, or that the PCB board messes with the reception of the controller antenna. Both results are fine. The boards will not receive copper pour on the front or back, as that significantly lowers the WiFi performance.

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