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DIY Nitrox Analyzer (Arduino based)

Discussion in 'Making your own Gear' started by Pao, Apr 12, 2019.

  1. Pao

    Pao Manta Ray

    # of Dives: 200 - 499
    Location: Manila, Philippines
    973
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    Here is an Arduino based Nitrox anlyzer I recently made. It uses an Arduino Nano, an ADS1115 ADC, and a 0.96" I2C OLED display. It uses the PSR-11-39-JD sensor from DGX. This is loosely based on this one: Arduino oled nitrox analyzer - Eunjae Im. But the code was too complex for me, so I decided to write my own simpler code and display the actual sensor reading in mV as a final check (because I am obsessive about knowing what lies under the hood) .

    It auto calibrates at startup and has on-demand calibration via a push-button. I decided not to store calibration values after power off as a safety precaution. It has gone through several iterations and ended up with the sensor and sampler built-in but with an external port. It is powered by an 18650 cell which can be charged via a micro USB port. It uses ~25 mA at full draw.

    Included in the pics is one with an external sensor input only and powered by 2 AA batteries and a 5V boost converter and another one using a hacked PM128 panel meter (Oxycheq El Cheapo clone).
    001.jpg 002.jpg 003.jpg 004.jpg 005.jpg
     
  2. Pao

    Pao Manta Ray

    # of Dives: 200 - 499
    Location: Manila, Philippines
    973
    200
    43
  3. michael-fisch

    michael-fisch Barracuda

    # of Dives: 2,500 - 4,999
    Location: Germany
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    Nice work, and I think that you did a good job.

    But, what is the advantage over a 3.5 digit DMM circuit with a 10 turn pot, battery and sensor?

    Michael
     
    Pao likes this.
  4. Pao

    Pao Manta Ray

    # of Dives: 200 - 499
    Location: Manila, Philippines
    973
    200
    43
    The main advantage is auto and 1 button calibration, no more fiddling with a knob. Other advantages are the readability of the OLED in bright light and USB charging. You can also roughly gauge the remaining sensor life at it directly displays the cell voltage. Components are also off the shelf and easy to replace/troubleshoot (I did a fair bit of that).
     
    michael-fisch likes this.
  5. stepfen

    stepfen Barracuda

    # of Dives: 100 - 199
    Location: Greece
    377
    168
    43
    Very nice. Have you thought/seen anything including CO measurement?
     
    Coztick likes this.
  6. Pao

    Pao Manta Ray

    # of Dives: 200 - 499
    Location: Manila, Philippines
    973
    200
    43
    Now that is an idea. There is an actual CO sensor called an MQ7. It can be my next project. :-D
     
    undrwater and Coztick like this.
  7. Pao

    Pao Manta Ray

    # of Dives: 200 - 499
    Location: Manila, Philippines
    973
    200
    43
    It was meant for use at room temp at 1 atmosphere, has an internal heater and needs bump gas to calibrate. It is slow and not really meant to be portable. :-(
     
  8. stepfen

    stepfen Barracuda

    # of Dives: 100 - 199
    Location: Greece
    377
    168
    43
    And I've heard cheap ones are not sensitive enough for us, as they need to be able to measure down to ppm (parts per million)
     
    Pao likes this.
  9. stepfen

    stepfen Barracuda

    # of Dives: 100 - 199
    Location: Greece
    377
    168
    43
    It would be a great project though...
     
    Pao likes this.
  10. JMBL

    JMBL Solo Diver

    # of Dives: 500 - 999
    Location: France
    376
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    Nice project and thanks for sharing. What about the next step ? A trimix/oxy analyser, for example ? :wink: Seen one done, arduino based, on a French forum.
     
    The Chairman and Pao like this.

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