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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

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lemonie

11 years ago

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?

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VIRONlemonie

Reply 11 years ago

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)

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lemonieVIRON

Reply 11 years ago

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?

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VIRONlemonie

Reply 11 years ago

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.

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kieranof

11 years ago

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

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VIRON

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

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lemonieVIRON

Reply 11 years ago

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?