3D printed case 
Laser cutted case
Our Arduino compatible CO₂ monitor can be used for independent measurements of the CO₂ content of enclosed spaces, but also in combination with phyphox for scientific experiments, for instance observing photosynthesis.
A list of the required components is given in the assembly instructions (Rev 1.1, in German). It consists of:
- finished board from a pack of three at Aisler (Rev 1.1),
- everything from this shopping cart at Digi-Key or at Mouser (but for a power supply),
- printing or cutting data for a case.
Boards (PCB layout) and components could just as well be ordered from other suppliers.
The CO₂ content is indicated with the following colors:
| green* | below 1000 ppm, |
| red | above 1000 ppm |
We have based the values on the recommendations of the Deutsche Gesetzliche Unfallversicherung. An elevated CO₂ content can be reduced by proper ventilation. The thresholds can be set as desired in the source code, the “sketch”:float topThreshold = 1000;float bottomThreshold = 600;
The assembly instructions also explain how to connect the CO₂ sensor to phyphox:
A CO₂ sensor experiment is automatically installed by tapping “+” in the menu and then “Add experiment for Bluetooth device”. It displays not only the CO₂ content but also the temperature and humidity from the start of the measurement (▶).
In the history tab, old data of up to 24 hours can be retrieved. Alternatively, the retrieved period can be limited to the past one, two or four hours.
The maintenance experiment could be used to perform a simple outdoors calibration of the CO₂ sensor with fresh air.
Resources (in German):
Further reading:
- Corona-Risiko im Klassenzimmer, ZDF heute Story
- A room, a bar and a classroom: how the coronavirus is spread through the air, El País
- Mit CO2-Sensoren gegen die Pandemie, Zeit Online
- COVID-19 Prävention: CO2-Messung und bedarfsorientierte Lüftung, Umwelt-Campus Birkenfeld
- assembly instructions of the previous board Rev 1.0 (in German)
The CO2 kit has been developed as part of the program “Qualitätsoffensive Lehrerbildung (Phase 2)” of the project “Lehrerbildung Aachen (LeBiAC2) der RWTH Aachen” supported by the Federal Ministry of Education and Research (Bundesministerium für Bildung und Forschung, BMBF) since 2019.