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Comment by barbazoo | Hacker News Reader

What would happen to an uncoated pi? Would the whole pi have to be coated? I just realized I know very little about that part of electronics.

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The problem with electronics in water is that water is an electrical conductor.

So the circuit diagram for the board becomes "everything connected to everything else all at once". Which means, at best it doesn't turn on. At worst it creates a short and current flows from one point to another, usually blowing up some part.

Electronics and water therefore are seldom friends.

Distilled water does not conduct electricity. It is the dissolved ions in the water that allow electricity to conduct. You may be able to clean the PI to such a level that nothing dissolves into the water when it is submerged.

https://techiescientist.com/does-distilled-water-conduct-ele...

Getting it that clean is hard. There's stuff like residual flux under the ball grid arrays and other surface mount components.

AFAIK electrolysis will force you to utilize a scrubbing system anyways once you've got current passing through the water. But getting conductivity acceptably low is much less demanding than getting it this extremely low. E.g. some CO2 lasers are cooled with purified water to limit the current through it.

That's true. The YAG laser I used in grad school had the flash lamp inside a water jacket, and the light went through the water.

I mean things like CW CO2 tubes running in the kV range and being immersed in water with exposed electrodes.

Even ultrapure water conducts electricity. It says right here [1] that its resistivity is 1.82×10^9 Ohm * m.

This is a pet peeve of mine. We get told of conductors and insulators in school, but it doesn't work like that. Pretty much everything except a perfect vacuum conducts electricity. It's just that some materials conduct electricity so poorly that it can be rounded off to 0 in most circumstances, but there can still be measurable current flow.

[1] https://en.wikipedia.org/wiki/Electrical_resistivity_and_con...

Ok, sure but 1.8 billion ohms puts you in insulator territory. Same ballpark as rubber or glass.

So no, you shouldn't really consider distilled water a conductor.

It's actually quite conductive when you'd try to exploit it's breakdown strength as coolant and insulation for high voltage power electronics.

A perfect vacuum conducts electricity as well: https://en.wikipedia.org/wiki/Schwinger_limit

Pure (eg. Distilled) water isn't a very good conductor at all. It's only when you add contaminant ions that it starts to conduct electricity in any meaningful sense.

Most people's experience with water rapidly destroying electronics is probably with highly ionised water such as sea water or water in the washing machine which has washing powder added.

Of course, it's worth pointing out in this case that as per the comments HZO claim they used water straight from the tap, so it's probably still an impressive enough achievement.

I'm curious how they went about sealing the external connectors (usb, hdmi), because surely those would need to be exposed and with the voltage present would act as points of corrosion. The pins on the Pi connectors are quite tightly spaced too. Maybe the AC nature of most of the signals helps there?

Electronic are dirty, your keyboard has a lot of junk, even salt from chips and pretzels, sugar from sticky fingers, etc. Spilling even distilled water on your keyboard dissolves all of that and makes the water conductive. Luckily some better laptops have channels (drip holes) for water to drain without affecting the board, but relying on bad conductivity of distilled wated in real-life scenarios is really not safe :)

I considered digressing into this in my post, but while completely true, I concluded its also irrelevant to the point being discussed. Even tap water has sufficient contaminants to make it an excellent conductor.

Outside of very clean, very lab, conditions, water conducts really well.

But your point is a nice aside, and I'm glad you brought it up.

Incidentally -drinking- pure distilled water tastes funny.

Plus even if you use distilled water, it'll probably find something to disolve a bit of if you keep in on your electronics for long and then it'll conduct a lot better.

Once you have your ultra pure water, and are willing to commit to maintaining the apparatus that keeps it that way. There is a second problem, extremely pure water is surprisingly corrosive, A laymans explanation is that it would be happier with a few ions, and will gleefuly strip them off any exposed metal.

Which is a shame. It would be nice if water could be used directly in an immersion environment. Much better thermal properties than anything else, and no mess,

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