Arduino oled nitrox analyzer

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• Hi there!

  I want to build one :)

  However I do not have a CCR cell like you do. Would this do: http://www.goodluckbuy.com/o2-a2-oxygen-sensor.html
  Or would you recommend something else? That considering that a complete NRC O2 analyzer is 120$ :)

  Thanks!

  Pat

  • The sensor on the link seems only measure between 0~30% which is useless for diving application. You better get sensor from Teledyne or Maxtec like this one https://www.oxycheq.com/analyzers-sensors/sensors/r17s-oxygen-sensor.html
    I know there's lot of cheap commercial o2 analyzer but many of them using analog circuit with cheap potentiometer.

• Thanks! Duh :) It completely make sense to get one that actually measure the proper range!

• Hi,

  Building a NX analysor based on your schema, so far so good.

  What did you use to put onto your revo cell? I will reuse my revo cells that are getting swapped.

  Thanks,

  Arlindo

  • If it's mean connector then I use Molex 5051 (3 pin). You can easily find same connector from computer part.

• Hi there!

  It's all good!! :)

  I see you changed the display code from the video you posted to the actual code here :D

  Can you confirm you only changed cosmetic display stuff and nothing important in the various calculations performed in the code?

  It's pretty neat! I have quite a lot of fun putting it together, I imagine how you feel actually coding it all :D

  Next step is to solder it up and put it in the box...

  I have one more question: I also see you removed the max O2 display in the video. I understand we don't need that info from a practical point of view. But nevertheless we still keep the clearing max result capability. Could you elaborate a bit why we actually need to clear the max O2 value and how it i used/purpose here?

  Thanks a million!!!

  Patrick

  • Hi, I update the code on post too. You can download it.
    Max result is useful sometime if I forgot to lock the screen.
    Have fun with your project. :)

    • Super cool :)

      One last question (sorry!) : the NRC O2 sensor I have specify a Recommended Load resistor of 10KOhms.

      To achieve this spec recommendation do I put a resistance in parallel between the O2 Cell wires?

      That's what I believe but I am no pro at all..!

      • Yes. You can put register between o2 wire. I don't think register is must but it will not hurt too.

• Hi,
  In your opinion this sensor http://www.cambridge-sensotec.co.uk/shop/ax300/208-r17-med-oxygen-sensor.html can be work fine?

  One last question: what apre the difference between r-17s, r-17van, r-17med, etc... etc...

• Hey :)
  For my test-setup I'm using the sensor of an old OxyCheq Handheld and am experiencing quite some delay in the readings. Returning back to 20.9 from 19.0 takes about five minutes despite venting the sensor with fresh air.

  Things seem to improve when I put a 10 kOhm resistor in parallel to the sensor - at least regarding the speed - unfortunately at the cost of reading stability. So either I have a slow sensor or one with large drift in the readings.

  Any idea what the problem might be here?

  TIA,
  Peter

  • 5min seems way too slow. How old your sensor? I would check with sensor output behaviour with normal voltage meter.

    • Yes, it's quite old and most likely that's the problem. Measuring the voltage directly it also behaves kind of sluggish. I will try to get a hold of a newer sensor and see what it's like with that ☺️

• Thanks for posting this project. I built it and it is working perfectly. I made a few small modifications to the program: (1) increased the time to release the button on "CAL" from 1 to 2 seconds because otherwise I sometimes inadvertently changed the limit PPO2 value. (2) Max PPO2 always starts at 1.4 bar instead of retaining the last value of the previous use.

• Thanks for the project docs. I just finished it to replace a defunct old analog analyzer.
  I had fun modifying the code to move text around on the screen to work with my two color display and change the MOD measurements to feet from meters. This is way more feature rich than most commercial units at 4 times the price. Now to solder up a final version and print a box for it. Thank you!!!

• Looking forward to trying this. Much cheaper than buying another oxycheq!

• Any suggestions for changing meters to feet in the code?

  • Find "Calculate MOD" function and change multiply value 10 to 33 (it'll look like this).
    float cal_mod (float percentage, float ppo2 = 1.4) {
return 33 * ( (ppo2/(percentage/100)) - 1 );
}

    And change "m" to "ft".
    display.print(F("m ")); -> display.print(F("ft"));

    Hope this help.