Oxygen content inside a sealed SMALL space

Using Arduino Project Guidance
1

Dear all,

I would like to measure the Oxygen content % inside a small closed space(imagine a sealed box for example). I will need to log the data for a certain period of time and thereafter to be able to export them to a PC once the experiment is finished.

I was wondering if I could use Arduino board with some sort of shield or sensor attached, put it inside this sealed environment and after the "experiment time" is lapsed, open the box, transfer the data to a PC and analyse them.

I made some research but everything was about measuring the % Oxygen in the office or in a "big" space. My box is tiny, so I need something "compact" and with a good autonomy.

Any insights will be really appreciated.

really thanks a lot in advance to everyone that might give even a small contribution.

M.

2

I see a lot of car oxygen sensors, you could tap the side of your container and install one to keep the test unit sealed.

Do some research there, see if those would be usable.

3

https://www.google.com/search?q=o2+sensor+testing&sa=X&biw=1438&bih=744&tbm=isch&imgil=Yv1eJwghCkI_uM%253A%253BFcNnhB6J85eeWM%253Bhttp%25253A%25252F%25252Fwww.autodiagnosticsandpublishing.com%25252Ffeature%25252Fo2-sensor-testing.html&source=iu&pf=m&fir=Yv1eJwghCkI_uM%253A%252CFcNnhB6J85eeWM%252C_&usg=__qjBbV0Ki1Wa5rtMdp5y7JSodw6Y%3D&dpr=1.1&ved=0ahUKEwjykL2EvefQAhUHjFQKHYEnAo0QyjcISw&ei=eNRKWPL0LIeY0gKBz4joCA#imgdii=zi0ubrpA1KmPqM%3A%3Bzi0ubrpA1KmPqM%3A%3BTHFMOkeGBuZAKM%3A&imgrc=zi0ubrpA1KmPqM%3A
I'm sure somewhere in here is something that will help in getting more than a good/bad reading out of a sensor!

4

CrossRoads,

Thanks for your insight.

Unfortunately, I cannot do that because the box is not strong enough and also the experiment needs to be done for a soft bag too for example (imagine the one you breathe in and out?)

My apologies I did not specify properly.

Let's just focus on putting a "system" inside a "closed" space.
I specified "closed" because I cannot run a cable from inside to outside.

Thanks.

5

This device is bulky and expensive, but also precise, repeatable, and easy to interface with Arduino.

6

Chris,

exactly something like that but they are too big if I combine with the Arduino board and occupy lot of space...

7

Quick and dirty version:

Sensors, something like an R22, or one of the many clones (or an R17 if you want smaller), buffer the readings with an op-amp (you'll want to amp it up anyway, output in air @ 1 bar is ~11mv).

Assuming you're surrounded by air, you could send the readings using a bluetooth board, or if you prefer wifi, maybe do it with an ESP8266.

You might try googling arduino ccr controller, its been done a few times :slight_smile:

8

LordKelvin:
Chris,

exactly something like that but they are too big if I combine with the Arduino board and occupy lot of space...

I am currently using the Vernier CO2 sensor, which I have removed from the plastic housing, and run from a tiny 85 and a dual op-amp (2 chips, 2 caps, 4 resistors, a pot and a switch. The sensor I use is about 1.75 inches long, half an inch high, and half an inch wide. It appears the O2 sensor is even smaller. But it is pricey!

9

http://www.cambridge-sensotec.co.uk/shop/ad300/176-r17-van-oxygen-sensor.html

£41.

You'll find most galvanic sensors are around £40-60. Typical life is ~18-24 months (you can get longer, despite what the literature says).

10

It depends on what range of O2 concentration you want to measure. 0-25% (normal atmosphere to oxygen depleted) is pretty easy and cheap. 0-100% (enriched atmosphere) is more expensive but should not be too hard to meet your requirements.

co2meter.com, despite the name, has a good sensor for the 0-25% range.

{edited to fix URL}

11

Dear all,

I do apologise for the late reply.

As I am the one running the experiment for the R&D I made a decision to put less strict condition on it. At least to have a first clue on what's going on.
Also because the stand-alone logger and sensor are massively expensive (we are speaking about 500+ pounds).

  1. I dod not need anymore a "soft bag", so I probably will use something (with the same volume) but more handy, let's say a plastic airtight box?

  2. I CAN now run a cable/wire from inside the sealed box to the outside and connect to an Arduino UNO to log the results.
    I still need to make air tight the hole where I will run the cable though! But it should not be too difficult.

Now I will reply to some of you:

ChrisTenone:
This device is bulky and expensive, but also precise, repeatable, and easy to interface with Arduino.

Yes and I found a Vernier shield that will allow a straightforward connection between this sensor and the Arduino UNO. Now I will need to understand HOW to log the date for example on a SD card???

We are around 300£ here.

scrumfled:
Quick and dirty version:

Sensors, something like an R22, or one of the many clones (or an R17 if you want smaller), buffer the readings with an op-amp (you'll want to amp it up anyway, output in air @ 1 bar is ~11mv).

Assuming you're surrounded by air, you could send the readings using a bluetooth board, or if you prefer wifi, maybe do it with an ESP8266.

You might try googling arduino ccr controller, its been done a few times :slight_smile:

This is a cheaper option: http://www.cambridge-sensotec.co.uk/shop/ad300/176-r17-van-oxygen-sensor.html

The thing is I will need to investigate and "play a bit" with the board and sensor and some tutorials in order to understand HOW to make it works. Of course, all this new knowledge will be an added value for my future projects... BUT it will need more time.

We are around perhaps 70-80£ total here.

scrumfled:
http://www.cambridge-sensotec.co.uk/shop/ad300/176-r17-van-oxygen-sensor.html

£41.

You'll find most galvanic sensors are around £40-60. Typical life is ~18-24 months (you can get longer, despite what the literature says).

See previous quote :slight_smile:

MorganS:
It depends on what range of O2 concentration you want to measure. 0-25% (normal atmosphere to oxygen depleted) is pretty easy and cheap. 0-100% (enriched atmosphere) is more expensive but should not be too hard to meet your requirements.

co2sensor.com, despite the name, has a good sensor for the 0-25% range.

Ideally 0-100% but I believe 0-25% will work as fine as well.

FYI, I could not reach your link.

OK guys so let's start from the new "rules" (less restrictions) of the project :slight_smile:

And, obviously any more insights or suggestions will be really appreciated, just simply to say "don't do this if you are not expert because you will take 2 months to learn (I do not have 2 months :slight_smile: ) etc.

Thanks a lot to everyone participating on this thread.

Mario

12

Oops, sorry. I meant co2meter.com. US-based (Florida) so there may be better shops closer to you. They mostly seem to re-sell European sensors.

13

To be honest, this is actually simple as hell..... you're probably overly worried :slight_smile:

Kit:

O2 cell
op-amp with impedance matching on the amp input
arduino... into the adc.

If you dont want to build it, you can buy commercial oxygen analysers (aimed at divers), from the likes of vandagraph etc (thats a complete unit including display etc)

The gotchas;

  1. the oxygen sensors effectively measure the partial pressure of oxygen, so if you overpressurise the housing it'll read over. I'd suggest using a flexible bag or an overpressure valve.

  2. All galvanic sensors are sensitive to moisture, so be aware of that (especially if its related to a breathing loop).

  3. Sensors age, so you need to calibrate in known gasses before use (ideally 100% o2).

  4. you need to ensure your gas in the chamber is the gas you want to mix, usually you do this either by flowing through a constant stream, or flushing the bag/chamber.

Some questions;

how frequently do you need to log.
how long do you need to log for
how accessible/openable is the housing
Can you put a circuit inside the box (Im thinking batteries here).

Subject to those replies, I'd be tempted to use an ESP8266, op amp front end... then just log the data over wifi to thingspeak or whatever server you prefer. its pretty simple

14

What about something based on absorption of light such as here? Either buy it (but they say $2000) or find something cheaper or build your own.

15

Good morning to everyone and Happy New Year!

Just a quick update on this project.

I am obvious taking in consideration all of your advice, gather them all together and I will make a decision.

I am prone to use an Arduino system of course.

I do have a question: I would like to buy a SD card module from GearBest and I would like to ask what size of the SD card I should buy?

8Gb. 16Gb, 32Gb?

I need to just log oxygen values every 2-5 secs for lets say 2 months...just to have an idea

Thanks a lot

16

A second question:

If I am using an LCD shield...the instructions state that the LCD will use pins 4,5,6,7,8,9 and A0.

Does it mean that I CANNOT use those pins even if I can see them "FREE" to put a jumper in on the LCD shield?

I thought that when I use a shield I could actually have ALL the pins available "again"....

Please may someone explain to me I got a bit confused...

Thanks a lot

17

No, the pins are conducted through to all shields so that you can stack them in any order but once a shield has taken the use of a pin, it's not useful for other shields. The exception is the bus communications like SPI and I2C.

18

Thanks a lot Morgan!

19

Dataspace required....

a reading every 2 seconds will mean about 30 million measurements in 6 months.

If you only used a 16-bit number ( an unsigned int ) per measurement this would be 60MB.

Any modern SD card is massively bigger than this!

regards

Allan

20

Hi again!

Don't know if I missed it...

What about this solution:

http://store.linksprite.com/oxygen-o2-sensor-module-of-linker-kit-for-pcduino-arduino/

Will it work?

It seems quite straightforward "on paper"....

Any advice or impression will be really appreciated guys.

M.