For a long time, I've kept a co2 meter on my desk to monitor the air quality (or lack thereof) in my office. I have now upgraded this a bit and this is a short post about that project.

It started a few weeks ago, when I was inspired by a video on youtube. Creator Allen made a beautiful display based on a rgb led matrix display and I immediately felt that I needed (to build) one as well. This Ascension Day long weekend, I finished it.

Except for the fact that my soldering is terrible, I'm very happy with the finished result. I designed the case using tinkercad and printed it on my Prusa MK3S+. Initially, I has placed an order on the 5mm pitch version, but thankfully I realized that that would have been too large for me to able to cover the screen the with a single piece, so I changed the order to the 3mm pitch version.

Electronics-wise, I opted for a Pi Zero 2 W, with the Adafruit Hat as that does a lot of the job for me. I added a power button with an LED and a rotary encoder I can use to provide some input to the software.

I also chose to put in some cables to expose the USB and HDMI ports of the Pi Zero to make it easier to access.

The most important piece though, is the co2 meter. Initially I had thought of using the one I already had, but I found a smaller one that would make a better fit. In my first version of the case, I placed it behind the display - but it turned out that the screen gets so hot, it skews the temperature measurements quite a lot. After moving the sensor to the base of the case, it's only about 2 degrees over ambient, thanks to the heat of the Pi.

I have learned more about 3D printing, a lot more about soldering, electronics, i2c and the Raspberry Pi GPIO ecosystem. I haven't really done anything like this since high school. Software-wise I'm still in the process of writing and cleaning up code, but I'll push it up on github in the near future.