Aevoc: measurement Interpretation & addon: MH-Z19

[der-lotse]

Dear Pina,

thanks for this great project, I really enjoyed it!
So, I kept going on and, by now, my AEVOC is still not mounted in a box but I added a real CO2 sensor and changed the code to work for me and also followed your suggestion and set up an mqtt/node red on my "NASPI" (raspi 4), so I can follow the evolution of the recorded data over time.

Now, I just wanted to comment on my findings of those: unfortunately I find the VOC sensor quite sensitive to any kind of organic molecules, odor.. we have a cat, but also cleaning the flat, drying loundry in the same room, cooking..makes the VOC shoot up. But since CO2 is only guessed, based on the VOC value, this CO2 value is not really reliable. So I added an MH-Z19 CO2 sensor and now I would say this is a really good help to judge about aerosol concenration indoors.
A problem with the particle sensor is, that it detects any particles with a certain size. That means, since a while it is a really good pollen detector ;) Which is actually good for me, because if during mornings room venting the particle count shoots up while CO2 goes down, I know I should take some anti-allergy medication before leaving the house.

Altogether, this is a real fun project with much more functionality - but the interpretation of measured values requires always some thinking, too.

Just a comment about the MH-Z19: I'm a crappy programmer and didn't work much with arduino like devices, so far.. first, I didn't manage to make it run when connected to the free pins D0 as RX and D1 as TX using softwareserial, so I took the pins D9 and D10 using softwareserial and a driver i found on the arduino website. This made debugging my code a bit tricky because this blocks communication with my pc.. If you had an advice here? Are there alternative pins allowing to communicate via UART without blocking the communication via the usb-rs232 interface?
Another problem is, that sometimes communication with the CO2 sensor is lost, so I needed to add another check-if-alive-otherwise-reinitialize to make it continously working.
Still, it was worth it: the sensor works quite excellent!

Well, thanks for all this!
I'll keep following you all on c't and c't uplink.

best
Chris