CO2 Sensors


Thread Starter

Dylan Gordon


I'm pretty new to all of this, but at any rate, I'm looking at building a CO2/temperature/humidity logging/management system that will run off of my PC. For anyone who's curious, I grow chillies indoors, and in the quest for the hottest ones I can grow, I've decided it's time to get really technical.

At any rate.. I've found enough information that I think I can figure out how to build a device for logging temperature and humidity, interface it to my PC, and write the software to control the environment based on those factors.

The problem is the CO2 sensor. Is there a cost effective CO2 sensor that I could somehow interface with a PIC device (I have very little idea what I'm talking about, but I'm sure I'll learn)? The ones I've seen are in the hundreds of dollars and generally have displays/alerts/etc. I just want an easy sensor who's output I can monitor along w/ the outputs of the temp. and humidity sensors, and send along to the PC.

Anyone have any suggestions? All thoughts greatly appreciated.



You haven't said where you live, but if it's in the US, and you start buying stuff like this to grow plants indoors, don't be too surprised if
you got a no-knock visit from your friendly local SWAT team. ;^)

Willy Smith
Numatics Inc.
Costa Rica

Dylan Gordon

> You haven't said where you live, but if it's in the US, and you start buying stuff like this to grow plants indoors, don't be too surprised if

> you got a no-knock visit from your friendly local SWAT team. ;^)

Yeah, I suppose that would be a bit of an issue. Maybe I should call them first. Hehe. Hmm.. I've never had any problems otherwise, though, so.. Anyway, I could go out and buy a commercial CO2 monitor if I wanted to, but they're over $500, which isn't worth it.

Kiel-1, Larry

Hello Mr. Gordan.

Below are a couple of web sites that might offer some information regarding your CO2 control ideas. Vaisala is a higher end sensor in both cost and construction (industrial grade). Kele is actually a distributor for many product lines that include CO2 sensors. They concentrate more on the Building Automation Systems (BAS) and
generally are not as rugged. Both sites also offer some technical information.

I haven't actually installed either product so I can't comment on support, reliability, ease of installation etc. In general, the you will find the BAS manufactures use CO2 to assist with HVAC
control. A couple of uses are to open outside air louvers when the CO2 level gets to a certain level or to control the ventilation rate to an area like a conference room. Both of these uses address Indoor Air Quality (IAC) which is a pretty big topic in the HVAC business and sometimes in the legal system.

Good Luck.

Larry Kiel
Kennedy Space Center

Richard King

Hi Dylan,
I think if you can get a CO2 analyser for only hundreds of dollars it is worth the cost.

Building an NonDispersive Infrared Analyser is an option, it works on the principle of measuring the absorption of certain wavelengths of Infrared light by the sample.

Richard King.

Alesa Alusuisse Engineering Australia Pty Limited.
Phone: +61 7 3218 3555
Fax : +61 7 3236 0155
Email: [email protected]
Web :

Now that I've had my silly fun with your post, take a look at Sensors Magazine:

There is a product finder for any sensor you can think of. You might also check with some of the manufacturers that aren't specifically listed as CO2 sensor providers; they may have a device-level part you could use (since you mentioned a PIC).


Willy Smith
Costa Rica
Check out . We are one of the original companies who pioneered the area of low cost IR gas sensing for CO2.
Joe Arena, Director of Sales, Telaire

Simon Fowler

hi, we manufacture non dispersive infra red sensors. there is not really a cheap solution to the probelem. we manufacture co2 sensors, but you are looking at about usd450 for a useful diffusion sensor. my advice is to take up brewing beer or wine-making. this will get the co2 up nicely.

Simon Fowler
Voitgasse 4
A-1220 Vienna
Phone: + 43-1-2584502-15
Fax: + 43-1-2584502-22
E-mail: [email protected]
Our homepage:,,