DIY Nitrox Analyzer (Arduino based)

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James_SGP

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Here you go...you can see the 200mV reading, if I blow on the sensor it reduces (as expected). Any thoughts from anyone?
 

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NightShade00013

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Sounds like the resistor could be bad, do a continuity test with it and see if it shows open or not and then see if the resistance is correct. Also depends on which version of a sensor you have. Teledyne made one that had a higher output version called the R33 that was used in some readers. That one did not need any type of boosting for the sensor readings to be picked up by most boards. In fact the R33 would likely kill the boost boards we are using.


I am in the process of forking and expanding the documentation for the original meter made by ejlabs as well. The project seems to mostly be abandoned anyway at this point. Some of the original libraries changed how they function so going to try and get the code updated and my build will be with a split Yellow/Blue OLED so shifting some info to the top will be useful. Also going to try and make a version compatible with larger and smaller displays, as well as do a version that will show MOD in feet and meters for those people diving in a metric area but used to doing things in feet. I think the original code had some merits like showing the MOD so you have that fresh in your mind before going on a dive I may scrap some data and likely end up setting removing the ppo2 changes so that can only be done while the code is being flashed. Simple enough for someone to pick one and stick with it rather than being able to change it on the fly if they REALLY want to dive deeper they can always do the calculation manually. But that is the beauty of open source you can mod it to fit your wants and needs. I figure having a simple place with multiple configs will make it easier for some of the less technical people.
 
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Miyaru

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nitrox1.jpg

I built a first analyzer after testing several prototypes.

nitroxA.jpg

Standard startup display, oxygen level in metric percentages, metric MOD, ppO2 menu-selectable from 1.1 till 1.6
nitroxB.jpg

Air calibration (done at startup as well)
nitroxC.jpg

100% O2 calibration, cell value is stored in eeprom and used as 2nd point calibration.
nitroxD.jpg

Last menu option: voltages of all the sensors.
This box only has an O2 sensor built-in, software is the same for analyzer combination with helium and/or carbonmonoxide sensors.
 

wnissen

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Wow, that's really neat! So would the same box and screen be able to support O2 and CO at the same time?
 

Miyaru

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No, looking at the specs sheet, it's worth testing and see what the differences are. I'll try this one as well.
 

NightShade00013

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Very nice, still waiting on a sensor to come in so had to build a voltage divider to start tinkering (was told right now there is at least a 6 week wait due to manufacturer's shifting production to health field devices). I know for tec divers the higher ppo2 will be desirable but I am looking to gear more towards rec divers for now.

Also looking to build out so that it will work with at least 3 screen sizes but just regular old OLED, have a 128X128 a 128X64 and a 128X32 so that what ever is readily available can be used and still display the info without issue.

For those who are in the same boat as me waiting on a sensor but want to test the build a voltage divider is a very simple circuit. Use a 10K ohm resistor in R1 and a 75 ohm resister in R2 with a 1.5V battery (like a AA) and you will get around 11mv on the vOut which is what you will need to test your circuit. It's basically a dummy load or "sensor simulator" and the actual cost with a switch is about a dollar if you already have the stuff on hand. Below is a calculator if you want to build a different value for your test but for an O2 sensor the one I have will work just fine just add a switch in the line to turn it on and off.

Voltage Divider Calculator
 

stepfen

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Also looking to build out so that it will work with at least 3 screen sizes but just regular old OLED, have a 128X128 a 128X64 and a 128X32 so that what ever is readily available can be used and still display the info without issue.

Actually I was wondering about the screen too. Those quoted seem too small to convey all this info. Which screen are you using above @Miyaru ?? I can't find it. For prototyping I will be using an "old" 2 line LCD, but this colorful one is so much nicer.
Cheers
 

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