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Carbon dioxide sensor?? Answered

Hi, I'm working on a project that measures outdoor air quality. Wondering if anyone knows a CO2 sensor that's not too difficult to use with a microchip (bs2 or arduino)? or knows of any links to air quality projects (the ones on MAKE seem to be broken links..) thanks! Kiera


Why do you want to measure carbon dioxide, this is not usually an air quality indicator? An infra-red spectrometer might be your best bet, carbon dioxide absorbs strongly at ~2400 wavenumbers. Building one may be a pain, but infra-red LED for a start?

Sure. An IR LED, a prism or diffraction grating ("clear rainbow plastic"), a phototransistor, milliammeter, ... etc To calibrate / tune it to that wavelength use an IR camera and ... most important ... don't forget to exhale! (or use a dry ice cube , or just a pinch of baking soda + a drop of vinegar, or a cuppa that sticky brown gooey carbonated liquid from Hamburger Hell)

More thought: You can use a tungsten bulb as your IR source, you'd need filters of course, but water and polystyrene would do. Double-beam is the norm, but tricky without advanced optics... As my original comment why does CO2 need to be measured?

Kiera should answer that. Perhaps it's a safer science project than measuring noxious pollution (CO). Perhaps it's for experimentally optimized biosphere or school space research. Recently there was a contest challenge to survive locked up in a safe. Some of us want to KNOW exactly what we are inhaling. Etc.

thanks for the comments/methods. it's definitely helpful to get these responses. thanks again :)


11 years ago

"Limewater" is the name of a solution of Calcium Hydroxide that turns
from clear to milky when carbon dioxide is absorbed by it. This is rather
simple and if you can find a scientific chemical supplier then a small
bottle of Ca(OH)2 is plenty for making CO2 detectors. It may involve
detecting reflected light from the cloudy water using an LED and
a light detector (CdS cell, solar cell, phototransistor, etc.).

I'm guessing limewater is not a deadly poison but it IS a chemical and
deserves respect. After all, even H2O (water) "may cause burns, explode,
blindness, intoxication, inhalation maybe fatal, etc" to drown laughing see
DHMO (Water) hazardous chemical

You'd have to quantify airflow through your solution of limewater and the do a gravimetric analysis afterwards. End resrult for any method is : measuring CO2 concentration isn't easy on the cheap.
And for (your choice)'s sake stay well clear of dihydrogen monoxide eh?