DIY Gas analyzer

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jboneng

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As my two big passions in life is diving and building geeky stuff, there is sometimes a cross-over between my two hobbies, like my new project.
This is a breathing gas analyzer based on a arduino uno development board. The plan is to have one handheld unit that analyzes the CO, O2, H2O, CO2 and oil content in breathing gases, so far it only shows the CO ppm, but a medical grade O2 sensor is in the mail from Germany.

The first picture is the very first version, it basically just output the input value from the CO sensor, the second image is of the apparatus where I have tighten up the build making it more compact, made changes to the firmware so it displays the CO ppm and is powered by a battery instead from the USB (I have changed the battery setup from one 9v battery to 4 AA lithium batteries).

The part list is so far
1x arduino uno
1x 3.1" 16x4 LCD screen
1x Kuuco MQ7 CO sensor
2x KY-004 buttons
1x Prototype shield v.5

The O2 sensor I ordered is a Teledyne R-22AV




Fil 15.07.15, 22.13.58.jpg Fil 17.07.15, 17.30.36.jpg
 

The Chairman

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I'm interested... what's it going to take to measure He???

Fwiw, I've backwards engineered O2 meters. They are pretty straight forward. I would love to make them smaller and water proof, but I never got to that point and lost my work shop. I always thought Arduino would be the way to go.
 

tbone1004

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how are you going to handle the different gas flow requirements for each of the sensors to ensure that air is moving but not building pressure? Have been thinking about doing something similar and mounting it in a pelican case with a QD fitting on it, but haven't had time to get around to it. Looking forward to seeing your solution
 
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jboneng

jboneng

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I'm interested... what's it going to take to measure He???

Fwiw, I've backwards engineered O2 meters. They are pretty straight forward. I would love to make them smaller and water proof, but I never got to that point and lost my work shop. I always thought Arduino would be the way to go.

In theory making it read He percent is straight forward, just do the same as I will do with the O2 sensor (create a custom molex 3 pin cable that can be plugged into the arduino, add an op-amp for the signal and write the software), the problem is the price for a He cell suitable for analyzing breathing gas, the cheapest i found was over 200 $, which is more than what I am willing to spend on the project.
 

marcushall

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Are there any 3d print plans for a housing available? I have no experience with 3d printing yet, but it doesn't seem like it would be too complicated.

An arduino nano would certainly be capable of running this. You just need an analog input for the sensor, maybe a reference input as well, a couple of digital inputs for the buttons, and 5 outputs for the display. The nano is not only cheaper (< $4 instead of ~$25), but is also significantly smaller, for better packaging.
 
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jboneng

jboneng

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Are there any 3d print plans for a housing available? I have no experience with 3d printing yet, but it doesn't seem like it would be too complicated.

An arduino nano would certainly be capable of running this. You just need an analog input for the sensor, maybe a reference input as well, a couple of digital inputs for the buttons, and 5 outputs for the display. The nano is not only cheaper (< $4 instead of ~$25), but is also significantly smaller, for better packaging.
I was thinking about using a Tinyduino insted of the uno when the prototype is ready. For the housing I first have to work out how the mechanics needs to be, I need a chamber that will seperate the gas flow into two chambers one chamber that holds static gas at 1-2 bar and one chamber where the gas flows through.
 
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jboneng

jboneng

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A small update got the O2 sensor in the mail from Germany to day, so it was time to hook it up to the board. It was pretty straight forward, and didn't need any Op-Amp, got sensible readings when I, in software, configurated the referance voltage to Internal 1.1V. still have to figure out hov to calculate the 02 percent from the voltage reading, and the documentation for this sensor is hard to find on the internet.

Fil 28.07.15, 20.14.42.jpg Fil 28.07.15, 19.43.44.jpg
 

NAM001

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I too would be interested in your final product capabilities
 

Russoft

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Nice work! I was scared away from a similar project due to the cost of the O2 sensor, but that CO sensor is cheap! I think I'll build myself an analyzer too as life allows me the time! Nice to meet a fellow electronics geek!

Now you should get yourself an ATtiny or ATmega uC and make a compact version of the sensor :wink:
 
https://www.shearwater.com/products/swift/

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