My unit build

fantastic work there bud, not sure if ally is the best material for the can though, you need to keep the lime insulated to keep the temperature up, especially important in cold UK waters.
 
It is looking rather good.

And makes me want a larger lathe & mill. Ah well.

Good point on the ali can. As kids we used to stuff aluminium foil into a bottle, then fill up with caustic solution and whack a balloon on the top. The NaOH eating the aluminium would generate hydrogen in large quantities as the foil rotted away - enough to inflate a couple of balloons off a 1l glass coke bottle.

Free hydrogen in an oxygen rich environment will be /fine/, though - it couldn't possibly end badly. :devilban:

Just be careful what comes into contact with what, and remember this little bit of chemistry if you ever get a flood :(
 
In practice, I dunno how violent that would be. Has anyone tried some sorb soup on bare ally? The surface area to volume ratio compared to scrunched up tinfoil is in our favour and sorb isn't entirely NaOH.

davydiver said:
fantastic work there bud, not sure if ally is the best material for the can though, you need to keep the lime insulated to keep the temperature up, especially important in cold UK waters.
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I see what you're saying, however it is insulated by the exhale gas all around the outside, same as a meg, jj etc. The sorb also helps itself on that score being a radial design.
 
You're right - it might not be that bad.

But worth checking to get rid of the nagging in the back of your mind. Make up some sofnosoup and leave it on a scrap of the same grade ali as you used for your can... see what it looks like after a couple hours.
 
WFO said:
In practice, I dunno how violent that would be. Has anyone tried some sorb soup on bare ally? The surface area to volume ratio compared to scrunched up tinfoil is in our favour and sorb isn't entirely NaOH.
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My dad experienced a good flood in his first HH, there was no anodizing left at the end of the dive, not sure how "violent" it was, but there was plenty of corrosion.
 
CCR Josh said:
My dad experienced a good flood in his first HH, there was no anodizing left at the end of the dive, not sure how "violent" it was, but there was plenty of corrosion.
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you are correct , a caustic solution will very quickly remove anodizing , it will also start corroding the aluminium if left to long although this is not instantanious, if you flood the unit or have a particularly wet scrubber ,wash properly after. i pretty much solved this problem by coating the inside with a 2 component polyurethane which is caustic resistant ,problem solved .
mike
 
michael hearn said:
you are correct , a caustic solution will very quickly remove anodizing , it will also start corroding the aluminium if left to long although this is not instantanious, if you flood the unit or have a particularly wet scrubber ,wash properly after. i pretty much solved this problem by coating the inside with a 2 component polyurethane which is caustic resistant ,problem solved .
mike
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Sounds like a great idea!
 
I thought about doing something like that but figured the cans are cheap (unlike the aurora work of art I presume you're on about Mike!) so "meh" if it floods I'll have bigger worries than the surface finish inside the can!

And also hard work to find a finishing material that is not at risk of off gassing. I've tried to be careful to keep all plastics known safe and avoid glued joints and such.
 
WFO said:
I thought about doing something like that but figured the cans are cheap (unlike the aurora work of art I presume you're on about Mike!) so "meh" if it floods I'll have bigger worries than the surface finish inside the can!

And also hard work to find a finishing material that is not at risk of off gassing. I've tried to be careful to keep all plastics known safe and avoid glued joints and such.
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yes i am on about the aurora , but listen, cheap cans or not it saves that extra work by not having to replace them , there have been some discussions on off gassing so im not going to get into that one , one extra piece of adivice for alu parts use some anodes this is really effective .go the extra mile it will be worth it
mike
 
PPo2 monitor code is still driving me barmy.
Think I might need to admit defeat and ask avr-freaks about it...


I'm in two minds as to the value of having a secondary KISS style triple-DPM display. (to be replaced in time with a deco-calculating jobby :))...
 
Ask here first - I get the impression there are a few sufficiently nerdy types that you might get answers.

Plus I'm curious to see what problems I'm likely to encounter as I head down that path myself in months to come. :)
 
So a serious design bureau meeting among the execut... (alright alright me and my mate had a few tinnies and a chat)...

Where we got to was to that the electronics should be changed a bit, no trimpots. Now thinking the ATMEGA can communicate with an AD5233 multi digipot chip via SPI interface and this can trim out the opamps. Several advantages to doing it this way, like no holes required. I can put 3x nice robust piezo switches into the handset, no need to open the case, ever.
The whole lot potted into a lump for robustness. Wet charge via bridge rectifier and charger IC.

Back to board design...
 
wet charging is ok, but watch out for off-gassing.

also if you're sleeping at all, bear in mind the next few adc cycles are 'iffy'
 
Hadn't really considered offgassing of the cells, I'll look into it cheers.

I'm thinking of making the HUD a completely separate system which would pick up the op-amps output. The digipots are memory type, solid state so should add a layer of independance to it. Or maybe not, not decided yet. If I didn't do that, I could trim in software. Still that means more to go wrong in software, it's not my strong point...
 
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More milling on head, just a few more bits of plumbing to add and it's ready to test on o2.

w5vh.jpg


tac8.jpg
 
Are you giggling to yourself as you walk around the shop? Do you find yourself wandering over to touch it occasionally, just because it's awesome?

I think I would be by this stage in the project :)
 
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