Pages: [1]   Go Down
Author Topic: Precalibrated CO2 sensor  (Read 16264 times)
0 Members and 2 Guests are viewing this topic.
0
Offline Offline
Newbie
*
Karma: 0
Posts: 42
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Could you point me on some calibrated and easy to use CO2 sensor, preferably with some digital interface for long distance reading?

What I'm trying to do is to make cheap device that measures temperature, humidity and CO2 (air quality) on 3 points in an apartment with just one Arduino. For temp/humidity I'm thinking to use DHT22, nice, cheap and 1-wire sensor (for up to 20m distance). However for CO2 things are not so easy and I need little help here for choosing the right sensor.

This will be a part of my home automation system, that will control heating and ventilation.
Logged

Global Moderator
Netherlands
Offline Offline
Shannon Member
*****
Karma: 211
Posts: 13469
In theory there is no difference between theory and practice, however in practice there are many...
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset


What sensors have you considered allready?

What is cheap in your opinion?

- (dutch) - http://www.elektor.nl/artikelen-als-pdf/2008/januari/co2-meter.321797.lynkx

This leads to => http://www.figaro.co.jp/en/product/index.php?mode=search&kbn=1&type=30&id=213020

Logged

Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

Georgina Ontario
Offline Offline
Sr. Member
****
Karma: 5
Posts: 437
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Do you mean Carbon Monoxide? That might be an indicator of air quality. CO2 would only be significant in a sealed environment.

http://www.sparkfun.com/categories/146
http://www.futurlec.com/Gas_Sensors.shtml

Worth a look here as well.
http://www.robotshop.com/ca/ProductSearch.aspx?qs=gas

A Carbon Dioxide Sensor would make sense in a Greenhouse where a level of 1% or 1000ppm would make sense.

Atmospheric CO2 is typically 360 to 385 ppm.  (< .04%) It only becomes an issue when it reaches several percent of the local atmosphere.

Suggesting that CO2 is an indicator of "air quality" (unless in a sealed space) is a bit of a stretch .
« Last Edit: March 20, 2011, 02:55:10 pm by WillR » Logged

Just another Hacker

0
Offline Offline
Newbie
*
Karma: 0
Posts: 42
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Thank you for the answers. What I want to measure is the oxygen level in my bedrooms and in the living room. The bedrooms are small and in the night on closed windows the oxygen level drops a lot. I'm making a whole home ventilation system and would like to control the fresh air to the bedrooms based on some sensor logic. This way the system will work only when is needed and will save money for room heating or cooling.

I need an easy to use calibrated sensors, since I don't have the knowledge and the hardware to calibrate them myself. Preferably they have to use some digital communication for long distances like 1-wire. I would like to use just one Arduino for 6 point of temp/humidity measurement and 3 points of air quality measurements. These measurement points will be maximum 10 meters far from the Arduino.

I'm taking any advices.

P.S. Cheap CO2 sensor for me is something below $30-$35.
« Last Edit: March 21, 2011, 04:33:02 am by mishoboss » Logged

Georgina Ontario
Offline Offline
Sr. Member
****
Karma: 5
Posts: 437
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

O2 Sensors are not cheap. A little reading will tell you why.
http://en.wikipedia.org/wiki/Oxygen_sensor

Here is where you can see the relative percentages of atmospheric gas
http://en.wikipedia.org/wiki/Atmosphere_of_Earth

It looks like the sensors I pointed you at will do the job to the extent that you need.

Nitrogen 78%
Oxygen(O2) 21%
Argon < 1%
Carbon Dioxide (CO2) <.04%

Water Vapour -- 1% - 4%

So measure any contaminants and the humidity and have done with it. Dry air is probably more irritating than CO2 or CO. But you can measure by product build up. That is what the other sensors are for...

The sensors are cheaper than the the research time spent finding sensors too cheap and inaccurate to do the job.

Now you could have found out all of this by doing the google/bing/ask searches yourself.

If you did the searches and did not share what you found and why your search results were unacceptable you wasted my time and yours.

Negative results help too.
Logged

Just another Hacker

Global Moderator
Netherlands
Offline Offline
Shannon Member
*****
Karma: 211
Posts: 13469
In theory there is no difference between theory and practice, however in practice there are many...
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Quote
The bedrooms are small and in the night on closed windows the oxygen level drops a lot
Just make something mechanical to open the windows partly is much cheaper (saver) and consumes no energy. It will provide you with the necessary oxygen...

But if you want to do it the technical way you just can measure humidity.

C6H12O6 (glucose) + 6 O2  =>  12 H20 + 6 C02 

so the humidity indicates how much oygen is used and how much C02 is produced. You need some additional chem formulas to get the math right I guess. 
Logged

Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

0
Offline Offline
Newbie
*
Karma: 0
Posts: 42
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

I'm making ventilation anyway. I will use recuperator heat exchanger to save heating/cooling expenses and to suppress the outside street noise (the noise is noticeable when a window is open).

What you say about measuring CO2 via humidity and some math is really interesting. I'll definitely do some researches about this. Thank you about this info.

Meanwhile, I'm open for other suggestions.
Logged

0
Offline Offline
Newbie
*
Karma: 0
Posts: 10
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Hey,

First, in the name of full-disclosure, I do work for CO2Meter.com, so take everything I say with a grain of salt  smiley-wink , but I'm also a tinkerer myself and do love the Arduino platform.

I see what you're trying to do. CO2 is most definitely a fresh air quality indicator. The premise is that in a closed room the CO2 will rise (we exhale it) and it indicates that the room has stale air in it. Commercial forced-air ventilation systems integrate our sensors regularly for on-demand ventilation to save energy by only pumping in fresh-air when the air is saturated with CO2.

We offer some of the most cost effective sensors on the market, but unfortunately we can't touch $35 a unit. The absolute cheapest sensor would be the K22 model here:

http://www.co2meter.com/collections/co2-sensors/products/k-22-pwm-co2-sensor

It has a PWM output, but I'd recommend using the I2C interface. You'll have some issues with doing 10 meters of I2C communication, The inductance of the wire might blur the bits, so to speak, so you might have to get creative with a circuit to boost the voltage / use a differential signaling method such as RS-485. I'd recommend the K30 sensor, which features a UART engine that easily converts to RS-485 with a transceiver chip, but it won't meet your budget.

Let me know if you have any questions!

Andrew Robinson
Integration Specialist
CO2Meter.com
Logged

Andrew Robinson
andrewbrobinson.com

Global Moderator
Netherlands
Offline Offline
Shannon Member
*****
Karma: 211
Posts: 13469
In theory there is no difference between theory and practice, however in practice there are many...
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Hi Andrew,

Think you found specs for a new CO2 sensor here smiley   wrt to the price, maybe you can offer a Kit to be assembled for a special "Arduino" price smiley

Rob

Logged

Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

0
Offline Offline
Newbie
*
Karma: 0
Posts: 10
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Rob,

The only way I could see a kit being offered at a lower price is if there was a condition of no technical support provided by our company, but on a personal level I think these sensors are just too cool, I enjoy tinkering with them in my spare time. They all run I2C which makes them dead-easy to interface with and I actually put together an application note a little over a year ago showing how to interface with a Arduino:

http://cdn.shopify.com/s/files/1/0019/5952/files/Senseair-Arduino.pdf?1264294173

Honestly there are some really cool applications of CO2... here's something I did with one of our products a while ago:

http://andrewbrobinson.com/computer-controlled-air-conditioner/

The details are a little sketchy, I'm planning on writing it up a little better and submitting to HackaDay someday.

I've always thought building a sealed enclosure where you could monitor and control CO2 / sunlight / soil moisture levels / weight of small plants would be really fun. Plants grow faster in elevated CO2 concentrations and making kind of a "plant laboratory" would be fun for nerds like me who enjoy statistics and number crunching. Putting together that kind of kit would be a fun project.
Logged

Andrew Robinson
andrewbrobinson.com

Global Moderator
Netherlands
Offline Offline
Shannon Member
*****
Karma: 211
Posts: 13469
In theory there is no difference between theory and practice, however in practice there are many...
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

@Andrew
Cool project! and the I2C code looks really easy.

Quote
I've always thought building a sealed enclosure where you could monitor and control CO2 / sunlight / soil moisture levels / weight of small plants would be really fun. Plants grow faster in elevated CO2 concentrations and making kind of a "plant laboratory" would be fun for nerds like me who enjoy statistics and number crunching. Putting together that kind of kit would be a fun project.
There are certain people allways interested in growing certain plants smiley

But serious, you are right, here in the Netherlands the CO2 output of some energy plants is guided to large greenhouses, generating a lot of veggies. It is interesting to do this at home however I don't know a good source for CO2. Do you?  Think I'm not allowed to rebuild the central heater smiley-wink  A small fire extinguisher ?

Also educative for schools!

Quote
The details are a little sketchy, I'm planning on writing it up a little better and submitting to HackaDay someday.
Be sure to do that and let us know !

Logged

Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

Phoenix, Arizona USA
Offline Offline
Faraday Member
**
Karma: 39
Posts: 5551
Where's the beer?
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

@Andrew
Cool project! and the I2C code looks really easy.

Quote
I've always thought building a sealed enclosure where you could monitor and control CO2 / sunlight / soil moisture levels / weight of small plants would be really fun. Plants grow faster in elevated CO2 concentrations and making kind of a "plant laboratory" would be fun for nerds like me who enjoy statistics and number crunching. Putting together that kind of kit would be a fun project.
There are certain people allways interested in growing certain plants smiley

But serious, you are right, here in the Netherlands the CO2 output of some energy plants is guided to large greenhouses, generating a lot of veggies. It is interesting to do this at home however I don't know a good source for CO2. Do you?  Think I'm not allowed to rebuild the central heater smiley-wink  A small fire extinguisher ?

Also educative for schools!

Quote
The details are a little sketchy, I'm planning on writing it up a little better and submitting to HackaDay someday.
Be sure to do that and let us know !



You can buy CO2 in cylinders at any welding gas supply outlet (if you're willing to spend the money you can even get liquid helium). You can probably get away with "welding grade" (there's "food grade" available mainly for soda dispenser use - IIRC, it is "drier", and doesn't have any non-gas impurities).
Logged

I will not respond to Arduino help PM's from random forum users; if you have such a question, start a new topic thread.

0
Offline Offline
Newbie
*
Karma: 0
Posts: 10
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

cr0sh is correct, welding gas CO2 is dirt cheap. Our friends in the paintball industry have also ensured that a wide variety of low-pressure regulators, electrically actuated valves, and other goodies are available to us. Welding gas is reasonably pure, I wouldn't use it as a reference gas for calibration, but it's usually >99% CO2.

Anything with a flame produces reasonable amounts of CO2 honestly, that's all a commercial CO2 generator is, just a big flame, they are just careful to ensure the reaction proceeds to completion, else you get small amounts of CO as a result of incomplete combustion, which is never good.
Logged

Andrew Robinson
andrewbrobinson.com

0
Offline Offline
Newbie
*
Karma: 1
Posts: 37
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

They all run I2C which makes them dead-easy to interface with and I actually put together an application note a little over a year ago showing how to interface with a Arduino:

http://cdn.shopify.com/s/files/1/0019/5952/files/Senseair-Arduino.pdf?1264294173

You are THE MAN!  I just started building an incubator where I have to control CO2 levels.  After researching all of the available sensors, I decided I wanted an IR sensor for maximum life and accuracy.  I bought a K22-PWM from co2meter.com for $65 and have been thinking about the interface.  I used a Bus Pirate (see http://bit.ly/cRzjF2) for initial testing of the sensor over I2C (works great!).  I was about to start interfacing to Arduino when I discovered this thread.  Kudos!
Logged

Pages: [1]   Go Up
Jump to: