CO2 Monitor - circuit diagram / details

[Craig (Cam)]

Hi hive mind

I believe one of the caving group's have made their own CO2 monitor - does anyone have any info , or know who has

Cheers

Craig
(RFDCC / GCRG)

 

[Bob Mehew]

See CREG Journal 106 June 2019. Whilst Ian's worked OK in a mine, my attempt failed in a cave I think due to humidity impacting the electronics. I vaguly recall others have done work on the topic. I am embarrased to admit I have not followed it up after covid.

 

[Duncan Price]

I made one using this NDIR sensor: https://sandboxelectronics.com/?pro...art-5v3-3v-interface-for-arduinoraspeberry-pi and this Arduino clone which has a built in LCD and SD card for data logging: https://www.pololu.com/product/4009

I found the drift on the CO2 sensor to be a problem and the fact that it needs calibrating every 24 hours as a consequence meant that I have only every used it indoors.

 

[mikem]

CO2 is one of the harder gases to detect and many multimeters just assume it's presence from readings of oxygen. NDIR are better for CO2, whilst carbon monoxide detectors use the other two techs:

https://learn.kaiterra.com/en/air-academy/carbon-dioxide-sensors

 

[mikem]

Final comment on "Are any CO2 sensors actually reliable?" from start of this year - "I have 4 different co2 sensors and they all report different values. Not sure which one to believe but current technology for these seem flakey."

https://www.reddit.com/r/HomeKit/comments/16basma

 

[mikem]

Presumably similar to Duncan's design, readings are affected by temperature and humidity:

 

[ChrisJC]

I bought a commercial one for about £1000. There's probably a reason they are so expensive (aside from the fact it does O2, CO, H2S and CH4 as well)

Chris.