Scorillo47
commented
3 years ago Very cool!
Cheapest O2 concentration sensors are ultrasonic. We are using Gasboard 7500E sensors which are a few dozen $.
You can try to build your own O2 ultrasonic analyzer - a few people have tried AFAIK.
The main idea is that speed of sound depends on the gas concentration. You send an ultrasonic pulse using a small piezolelectric transducer using a microcontroller then you detect the travel time of the reflected ultrasonic pulse using the same transducer. You measure the time interval and from here you measure speed of sound.
With any ultrasonic sensor you need to do some calibration as speed of sound depends on the ratio of O2/N2/CO2/argon. You need to do calibration for the typical ratios from a O2 concentrator.
Most precise O2 sensors are fresh electrochemical O2 sensors but they are expensive as you've noted.
If we look at cheap methods, you can do O2 determination using a similar method that you describe. Simplest method to remove O2 from air is using oxidation of iron wool in a salty/wet environment which rusts and absorbs O2 from the air, but takes quite a while (days) to finish. But the iron wool method is the most commonly used method in labs AFAIK. Instead of iron wool you can use more expensive chemicals which absorbs O2 faster but they are toxic.
I suspect a similar technique could be used to absorb O2 from air using sodium sulfite/bisulfite/metabisulfite chemicals. These are very cheap and commonly used in the wine industry and can be bought in bulk. I have never tried yet this method though.
Burning a candle in O2 environments - I've tried that too but gives very imprecise results
Checking the temperature characteristics could work but is also very imprecise since temp sensors do not have good accuracy. I suspect this method has very bad accuracy as N2/O2 are quite similar and hard to tell apart.
From: Fawaz Ahmed @.> Sent: Tuesday, April 27, 2021 5:44 PM To: oxycon/ProjectApollo @.> Cc: Subscribed @.***> Subject: [oxycon/ProjectApollo] Cheap way to verify higher O2 concentration (#44)
Hi I was working on similar project last year, but by following this guidehttps://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Foxygenator.geprojects.tech%2F&data=04%7C01%7C%7C916a9b71b1244705de4008d909dec65a%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637551674674924065%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=YhIEzNJpwyxkoKhD%2BmROkkXPwI3cwLDwxzusZc4TEOQ%3D&reserved=0 (eventually I gave up the idea,as zeolite was only available in bulk)
Anyways the prototype I was thinking to make was exactly similar to your model (like using soda bottle, using silica gel columns based on this principalhttps://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.vmacair.com%2Fblog%2Fdual-tower-regenerative-desiccant-air-dryers-work%2F&data=04%7C01%7C%7C916a9b71b1244705de4008d909dec65a%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637551674674924065%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=LhnpJfE8KuW9zYocTkN9M6d0dl8LMjxRKtLShH32y9s%3D&reserved=0 etc)
one thing was that, oxygen concentration checking sensor was quite expensive, so I had to think of better way. I asked it herehttps://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fchemistry.stackexchange.com%2Fquestions%2F136905%2Fcalculating-the-amount-of-oxygen-in-a-glass-using-candle-burning-time&data=04%7C01%7C%7C916a9b71b1244705de4008d909dec65a%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637551674674934054%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=kVRZlG8LEqxt2H8U8D9Gv8eFkfvGqwwMk1KUcm0atZg%3D&reserved=0
And the idea was to use a cheap thermistor(which changes resistance with heat) to see the temperature of output gas, the more cooler gas the higher concentration as the O2 is cooler . I am not sure though its practical enough. I also thought of adding autocalibration in arduino code, which will adjust timings etc based on thermistor readings.
And had many mores ideas.
Anyways I just thought of sharing it, might be helpful to someone working on it.
Regards, Fawaz Ahmed
- You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHubhttps://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Foxycon%2FProjectApollo%2Fissues%2F44&data=04%7C01%7C%7C916a9b71b1244705de4008d909dec65a%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637551674674934054%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=gEqSE5o5L3lJaWbl6We5FJe4JFQNa%2BgJldrzvxrkuhA%3D&reserved=0, or unsubscribehttps://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fnotifications%2Funsubscribe-auth%2FAASECWP56H2JPKCBW7MVUQLTK5K6TANCNFSM43WAZV2A&data=04%7C01%7C%7C916a9b71b1244705de4008d909dec65a%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637551674674944048%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=EwjZuSqAiEQDojYjLALZBJWonHMcQrixl33X9LWwdb8%3D&reserved=0.
fawazahmed0
Hi I was working on similar project last year, but by following this guide (eventually I gave up the idea,as zeolite was only available in bulk)
Anyways the prototype I was thinking to make was exactly similar to your model (like using soda bottle, using silica gel columns based on this principal etc)
one thing was that, oxygen concentration checking sensor was quite expensive, so I had to think of better way. I asked it here
And the idea was to use a cheap thermistor(which changes resistance with heat) to see the temperature of output gas, the more cooler gas the higher concentration as the O2 is cooler . I am not sure though its practical enough. I also thought of adding autocalibration in arduino code, which will adjust timings etc based on thermistor readings.
And had many mores ideas.
Anyways I just thought of sharing it, might be helpful to someone working on it. And one more thing, you did a great job 👍
Regards, Fawaz Ahmed