DIY Nitrox Analyzer (Arduino based)

[Pao]

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).

 

[Pao]

GitHub link for the project with code and instructions: ppppaoppp/DIY-Nitrox-Analyzer-04_12_2019

Comments welcome!

 

[michael-fisch]

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]

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

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).

 

[stepfen]

Very nice. Have you thought/seen anything including CO measurement?

 

[Pao]

Very nice. Have you thought/seen anything including CO measurement?

Now that is an idea. There is an actual CO sensor called an MQ7. It can be my next project. :-D

 

[Pao]

Very nice. Have you thought/seen anything including CO measurement?

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. :-(

 

[stepfen]

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)

 

[stepfen]

It would be a great project though...

 

[JMBL]

Nice project and thanks for sharing. What about the next step ? A trimix/oxy analyser, for example ? Seen one done, arduino based, on a French forum.