CO2 Sensor with RGB indicator

We organised a workshop in our local hackerspace to build CO2 sensors with a bunch of people so you can take care of your air quality at home.

The sensors runs ESPHome so you can integrate is easily into your smart home like e.g. HomeAssistant but you can also just give it power and run it standalone.

All relevant files for the software and our presentation which we gave at the workshop and which contains the instructions (heads up: Slides are in German, but have quite a lot of images) can be found in our Gitlab Repository

Parts 

This case is designed for an Wemos D1 Mini v4 (v4 is important so you get USB-C) and a Sensirion SCD40. 
We tested quite a few different sensors and found this one to be the best (price, performance, size, features). When ordering dirrectly from AliExpress you should get the Wemos D1 and the SCD40 for ~$25.
You will also need a very small strip of WS2812 RGB LEDs and a few little pieces of small cables.

Printing instructions

Cover: Print it on it's front and make sure your first layer looks really good. I would recommend a rogh printing surface to hide all lines. No support needed

Clips: Easy print. You will need two of them.

Back: That's the tricky part. Rotate it flat on it's back for printing and add a little bit of support in two places (There is an image in the gallery which shows support). But heads up: The slots for the SCD40 and the Wemos D1 are rather tight! The PCBs are not always perfectly the same size and depending on your printer calibration you wont get something that fits. It's best to use the cut feature in your slicer and cut our the top part and the bottom part and do a quick testprint to check the fit.

Software

The sensor runs ESPHome. Check our Gitlab repository for the sourcecode.