My Nitrox Stick build

[jlcnuke]

Disclaimer - this is what I did/am doing, I don't offer this as anything more than information about what I am working with.

So, I decided I'd like to make nitrox, so I went and got a copy of the OHC, read a bunch of threads/posts on the internet, and watched some Youtube videos. Finally, I decided I would be comfortable and safe to make my own stick. I'll break this into two parts - the stick and the O2 Supply/Analyzer. Where possible/appropriate, I'll link to what I bought for this project as well.
(Caution - Large picture)


The stick:
Parts used -
John Deer Air Filter GY21435
1.5" pvc to filter adapter (3D print)
3" x 1.5" reducer
1" Bioballs
2' of 3" PVC pipe
5/16" hose barb x 1/4"NPT male brass coupler (1 here, the other used on the O2 side)
3" screen (3D Print)
3" x 2" reducer
2" x 1" PVC sleeve bushing
1" pvc pipe
1" x 1" x 1/2" PVC tee
1/2" PVC insert for PSR-11-39-JD o2 sensor (3d printed) (could replace this and the tee above with one that is drilled out for an O2 sensor to mount in however)
3" Clamp Brackets
Adapter and hose to go from 1" PVC to compressor inlet (varies depending on compressor, I plan on using 1" reinforced food grade hose, hose clamps, and appropriate adapters)
1/4" NPT tap, drill bits, PVC cleaner/glue, etc. were used as well. Also everything gets cleaned just because. 3d parts are sanded, washed, and cleaned to ensure they won't be having any stringing coming off etc.

When the smell dissipates, I'll also be using some scrap wood and the clamp brackets to mount it on the wall.

Parts were assembled (and glued as appropriate) pretty much in the order above, except I did not glue the 3"x1.5" reducer to the 3" PVC pipe. This is because I'm letting everything sit out for the glue odors to dissipate prior to putting the bio-balls in, and since it's a nice fit and just will sit on top of everything I don't think glue is necessary for it. The 1/4" NPT fitting was attached just far enough down to allow the 3" x 1.5" reducer to sit onto the 3" PVC pipe. If using larger bioballs or baffles, the 3" screen wouldn't be necessary as well. I could also find a different filter or attach it with a different method if I didn't want to 3d print anything there either.

 

[jlcnuke]

For the O2 supply and analyzer, I went with a DIY analyzer. I used this guide from Dive Tech.
For this I used my 3d printer but I could have put it in any case really. After getting things together, I think I'll be designing a different case for it with a display on the front instead of the top, as that would be more convenient.

To use this you'll need to know how to solder and program the Arduino with the supplied code in the Arduino software. To do that you'll have to add some libraries to the Arduino software. Additionally, the code has an error with the current libraries. So you need to change "Adafruit_ADS1115 ads(0x48);" to "Adafruit_ADS1115 ads;", as the 0x48 variable is hard coded in the library now. The parts, in my opinion, are cheap enough (outside the sensor), but you might want to see if any friends are interested in an analyzer as well since many of them are cheaper, per piece, when bought in 3-6 packs. In hindsight, it might have gone easier wiring things with something like this for the wires that go to multiple places, then just glue it in place.

I also made 2 other parts for this, a 3D printed new cover to allow for using a headphone jack on the analyzer and a PSR-11-39-JD o2 sensor on the other end of a 3.5mm plug.

Additionally, to go from the O2 bottle to the nitrox stick, I used the following:
An oxygen regulator
5/16" hose barb x 1/4"NPT male brass coupler (1 here, the other used on the stick itself)
5/16" food grade tubing with connectors
An isolation valve
a 3-30 lpm flowmeter with control valve

I mounted the flowmeter on a box on the wall and printed a wall mount for the o2 analyzer as well so I'd have my "control panel" with those items together.

Picture before running tubing and mounting it on the wall.

 

[jlcnuke]

One question I had recently, was "is it feasible to use an air pump to supply gas from the bottom/outlet of the nitrox stick to a Divesoft analyzer". It seems to me that, if doing that, I could put helium and O2 in at the top of the stick, measure it at the bottom (adjust flowrates as necessary) and mix trimix right in the one stick. Is there a downside to that I'm not aware of. Maybe something @tbone1004 knows of or someone else?

 

[tbone1004]

One question I had recently, was "is it feasible to use an air pump to supply gas from the bottom/outlet of the nitrox stick to a Divesoft analyzer". It seems to me that, if doing that, I could put helium and O2 in at the top of the stick, measure it at the bottom (adjust flowrates as necessary) and mix trimix right in the one stick. Is there a downside to that I'm not aware of. Maybe something @tbone1004 knows of or someone else?

What you normally do when you want to mix trimix is you put a pair of nitrox sticks in tandem. You inject He into one and O2 into the other and do it with just O2 sensors. Basically you either mix EAN32 in the first stick, then knock it back to whatever fO2 you want in the second with the He or vice versa. Usually He first. I wouldn't do it with an air pump personally though you could, and I really don't like putting He through a compressor. Biting the bullet for a booster and blending it that way is far more reliable and you can adjust mixes if you have to.

 

[Couv]

I really don't like putting He through a compressor.

Curious as to why putting He though a compressor is not desirable.

 

[tbone1004]

Curious as to why putting He though a compressor is not desirable.

surprising amount of blowby which is getting expensive and depending on how big the filters are, there is a lot of gas to go through before you get the mix coming out of the whips sorted out properly. It can be done obviously, but I think the paradigm of dedicated a pump to EAN32 at all times and using a booster for He is more efficient and accurate.

 

[BRT]

surprising amount of blowby which is getting expensive and depending on how big the filters are, there is a lot of gas to go through before you get the mix coming out of the whips sorted out properly. It can be done obviously, but I think the paradigm of dedicated a pump to EAN32 at all times and using a booster for He is more efficient and accurate.

Some high pressure compressors do not cycle the blowby back through?

 

[tbone1004]

Some high pressure compressors do not cycle the blowby back through?

I hope they don't since the rest of the stuff it would be mixed with is the oil vapors.....

 

[BRT]

I hope they don't since the rest of the stuff it would be mixed with is the oil vapors.....

I own a Kidde and a Bauer and they both recycle the blowby. I believe that on the K14 it is a critical part of the lubrication.

 

[tbone1004]

I own a Kidde and a Bauer and they both recycle the blowby. I believe that on the K14 it is a critical part of the lubrication.

recycle it where? Do you mean put it back into the first stage? I'll have to look at the plumbing since I haven't paid that much attention to oiled compressors in a while since I use Rix pumps.