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You don't say what you plan to monitor or what change you are looking for.  Assuming you are looking for background C02 levels

Having a quick look at the sensitivity graph would appear to show that the sensor only really becomes sensitive to CO2 at concentrations about 400ppm.  Given that current average CO2 concentrations are a little lower than that, if you are just looking to see atmospheric variations in CO2 levels you are unlikely to see any variation.  So whilst you might read some data, getting data that means something out of the device might be more tricky!

There are at least 2 groups working on this with the Air Quality Egg (available from the OpenEnergyMonitor Shop shipping a Nanode/Arduino Based solution, and Airpi doing a Raspberry Pi based version.  At least with both of these you are joining a community that can learn together.  Both these devices require you have an always on power supply to warm the sensors, they aren't going to work for very long on batteries.

Ok Thanks.  Yes it is internal / MHRVS concentrations I am interested in.  I'll look at those projects, thanks.  I had realised that battery powered was not an option for that reason.

Cheers

Bit more research! The Air Quality Egg is not currently available and the airpi does not have a CO2 solution.

Acceptable internal CO2 levels it seems, are around the 1000-1500ppm so this device should be able to measure it adequately.  So could it be hooked to a EmonTH (allowing for the need for a constant power supply)?  My electronics and low level device interface knowledge is a bit thin!

If it could, there is a gap in the market for a cheap CO2 monitor!

Being able to measure it, and being able to measure it accurately are two separate things.

If you look at the sample code it contains the following three phrases:

"This piece of source code is supposed to be used as a demostration ONLY. More sophisticated calibration is required for industrial field application."

"//two points are taken from the curve.
//with these two points, a line is formed which is
//"approximately equivalent" to the original curve."

"//These two values differ from sensor to sensor. user should derermine this value."  

i.e. you need to calibrate each sensor

There also appears to be no correction for temperature or humidity.

So if you are only looking for a trend, rather than an absolute value, it will do it.  

On getting the data into emoncms as there is code for the arduino, I'd suggest connecting the sensor up to an arduino and using that.  Looking at the arduino code it outputs variable called "percentage" ( which is actually a ppm). So you could look at some of the code examples on github.com/openenergymonitor on how to package up a variable into a URL to send to emoncm.  

Carbon Coop that we've been working with are also keen to include CO2 monitoring as part of air quality monitoring inside the houses they are retrofitting. I think Matt looked at the MG 811, would be great to hear if you get it working, it seems that one of the main issues from a measurement accuracy point of view is that they are un-calibrated, Carbon Coop mentioned the possibility of getting them tested in a lab, but as of yet we haven't progressed on it.

I think this one I am looking at has some sort of gain on it so you set it to the outside background CO2 level and use that as a calibration.  When external CO2 is around 400ppm and inside you are interested when it gets above 1500ppm the lack of absolute calibration does not matter.  Order of magnitude is fine for simply monitoring internal levels to determine if, for instance, the MVHR needs to be run at a higher rate.

@ukmoose, the key statement in that code is 'industrial field' I simply want an idea as to how high the concentration is for internal air quality purposes.  If the error was 10% it would not really matter.

So *could* the emonTH handle it (with a power supply)?

Hi,

Any return on experience concerning the usage of this CO2 sensor ?

Eric

The easiest way would be to use a 'commercial' off the shelf sensor.  They self calibrate, just power them up (usually 24vAC/DC) and over about a few weeks they self calibrate themselves.  They essentially all use the same sensor hardware from Senseair.

They come with a 0-10vdc or 4-20mA output to give you your reading.  Just use resistor divider network to get you down to 0-5v and a small cap to dampen the signal a little and you can read the value and convert accordingly using the ADC.  This is pretty much what the commercial controllers do but with a few added features to protect the inputs from muppets connecting stuff up wrong!

Most are setup off the shelf to read 0 - 2000ppm.  Fresh air is usually around 400-450ppm.

I have a number of faulty CO2 sensors here that I am slowly having to replace on a project where they are used to control natural ventilation in school classrooms so if anyone wants one to have a poke around with, PM me.  They also have a UART on the board but I wasn't quite sure how to talk to it so it may actually be possible to fix them.

Oh as a bonus they also read temperature too.

Hi,

Why not use an open source HW board like this one :

http://www.dfrobot.com/index.php?route=product/product&product_id=1023

Eric

Hi,

we are starting energy management project in Latvia where we will monitor energy and water consumption in schools. We are planning to use EMON stuff for monitoring temperature and use of electricity for different devices.

Training of personal and pupil about right ventilation habits in classrooms we want to base on measurements of quality of air in the class. Window and doors should be opened when quality of air is not good and the other way around.

It would be great if we could use wireless sensors for temperature, CO2 and current measurements using EMON TX or EMON TH and posting the data via RPI into CMS. With such a solution we could create an warning when the air quality is bad - OPEN WINDOW/DOORS or something similar... But it seems there is not a ready solution for that...

Does anybody has an idea how we could solve our need for CO2 data and sending it to EMONCMS?

Hi,

In theory, you can do it easily. You have to connect the analog output of a CO2 sensor to the emonTX input and then write a sketch that will read the input. See an example here

I'm planning to try it in the coming months with one of those sensors :

http://www.dfrobot.com/index.php?route=product/product&product_id=1023

http://sandboxelectronics.com/?product=mg-811-co2-gas-sensor-module

http://www.co2meter.com/collections/co2-sensors/products/k-30-co2-sensor...

Take care  of the calibration phase which is very important when measuring CO2.

I will give feedbacks when done.

Regards,

Eric

Thanks for your reply,

As I got it from a forum OEM guys have some problems with CO2 sensors...

I have a problem to write a sketch... I can do just copy/paste and connect a wire:) I will wait for a news

Best Regards

ratniks

As I got it from a forum OEM guys have some problems with CO2 sensors...

Can you tell us more ?

The SenseAir K-30 seems to be a good sensor, not cheap though. www.senseair.se $85 at www.co2meter.com

Anyone completed integration of CO2 sensor with OEM ?

Anyone interested in a "groupbuy" for the CO2 sensor from SenseAir?
The distributor in The Netherlands is offering these prices:

Art. 030-8-0006          CO2 Engine K30 STA             € 105 excluding VAT

1 - 5 :                     € 105
5 - 25:                    € 95
25 - 100:               € 85
>100:                     € 75

We have been using for 1 year these sensors:

http://www.figaro.co.jp/en/product/sensor/application/air-quality-control/

Mainly there are 2 technologies: 

Solid Electrolitic technology (http://www.figaro.co.jp/en/product/entry/cdm4161a.html)   About 50 €

Adv: Really cheap, good accuracy (comparing with professional metering +- 100 ppm about 10%, good enough for buildings), 300 mW consumption. 

Cons: 2 hour warming before reading, sensor saturation in some years (unpredictable running)

Infrared technology (http://www.figaro.co.jp/en/topic/docs/20120412111228_39.pdf) Like Senseair About 80€

Adv: 2% of accuracy

Cons: 2 min warming before reading, not very cheap.

Recommended shop: http://www.co2meter.com/

Finally we have decided to use Senseair S8.

It is very easy to integrate in emonTH, it has its own arduino library.

Good luck! 

We have been using for 1 year these sensors:

http://www.figaro.co.jp/en/product/sensor/application/air-quality-control/

Mainly there are 2 technologies: 

Solid Electrolitic technology (http://www.figaro.co.jp/en/product/entry/cdm4161a.html)   About 50 €

Adv: Really cheap, good accuracy (comparing with professional metering +- 100 ppm about 10%, good enough for buildings), 300 mW consumption. 

Cons: 2 hour warming before reading, sensor saturation in some years (unpredictable running)

Infrared technology (http://www.figaro.co.jp/en/topic/docs/20120412111228_39.pdf) Like Senseair About 80€

Adv: 2% of accuracy

Cons: 2 min warming before reading, not very cheap.

Recommended shop: http://www.co2meter.com/

Finally we have decided to use Senseair S8.

It is very easy to integrate in emonTH, it has its own arduino library.

Good luck!