Ask Slashdot: How Do I Make a High-Spec PC Waterproof?

jimwormold writes: I need to build a system for outdoor use, capable of withstanding a high pressure water jet! "Embedded PC," I hear you cry. Well, ideally yes. However, the system does a fair bit of number crunching on a GPU (GTX970) and there don't appear to be any such embedded systems available. The perfect solution will be as small as possible (ideally about 1.5x the size of a motherboard, and the height will be limited to accommodate the graphics card). I'm U.K.- based, so the ambient temperature will range from -5C to 30C, so I presume some sort of active temperature control would be useful.

I found this helpful discussion, but it's 14 years old. Thus, I thought I'd post my question here. Do any of you enlightened Slashdotters have insights to this problem, or know of any products that will help me achieve my goals?

Comments

Water cooled!

[lgw]

Make it water-cooled! Duh.

Re:Water cooled!

[lgw]

Hate to comment on what was a joke post, but can't resist when geekoid is wrong.

The hard part of a sealed case is cooling. Any sort of air-cooling can't work, obviously. Passive cooling through the case is unlikely with a high-end video card. With water cooling you can have a very large heatsink separate from the sealed case (with the appropriate plumbing), and if jets of water are flying around, you could cool very efficiently by catching a few of them with the heatsink from time to time.

Yo dawg, we water-cooled your water-cooled case so you can ski while you ski.

Re: Water cooled!

[Anonymous Coward]

The original problem was underspecified.

Water cooling with or without an intervening diffusion system would work, but only if the water environment were constantly available. Ships use water cooling for their engines because it is reliably available, nearly free, and can be dumped right where our came from without harm. But this only works because ships are nearly always in their operating environment, and when they aren't, they don't start their engines. Doesn't work for seaplanes.

The proposed system seems small enough to be portable, so will want to work on the test bench. In any case, the OP didn't state the device would always be exposed to water.

BTW, mineral oil works great when it can be used. Long ago I needed to run a big full-wave power supply bridge at four times its rated capacity, so I removed the four diodes from their big heat sink and immersed them in a mayonnaise jar of mineral oil. (Heat sink wouldn't fit.) It worked fine for a great many years, mineral oil having much greater thermal transport capacity than air, and the mayonnaise jar having sufficient area to dump the heat into the air.

But servicing components inside a mayonnaise jar of mineral oil is neither a simple nor a neat procedure.

Re:Water cooled!

[Sqr(twg)]

This is currently modded "funny", but is actually a very good solution to the problem. With water-cooling, all electrical components, except the radiator fan, can be in an air-tight enclosure. Then get an IP rated fan, or a larger, fanless radiator.

Re:Water cooled!

[LWATCDR]

No but it you could use a heavy AL case with a lot of fins on the box and mount a large water block to the case. The case becomes the heat sink.
Or you could build large custom heat tubes.which would be more reliable.

Re: Water cooled!

[pla]

Water cooling with or without an intervening diffusion system would work, but only if the water environment were constantly available.

I don't understand why this thread has continued past the GGP's done-in-one correct answer.

Water cooling in this context doesn't mean dumping heat into environmentally-available water like a boat or nuclear power plant. It means you have hollow metal blocks on the hot chips, a radiator on the outside, and some fluid flowing through the system to move the heat from inside to outside. You can thereby make the case completely waterproof while still effectively dissipating heat.

Now, for a somewhat better question than heat dissipation, how does the FP plan to power this rig? Yes, you can easily use outdoor conduit and junction boxes to get electricity to places exposed to water, but you can't really make that portable.

Server Techniques

[BoRegardless]

Some servers have been designed to have the motherboard immersed/sealed in dielectric fluid in a sealed box to take the heat out, which would also be in a sealed structure. That stops the need for air as a heat transfer method. Would require waterproof electrical connectors.

Re:Server Techniques

[Mashiki]

I used to build cabinets for farm use, while I didn't go the immersion route I went with "the box" solution. Basically it meant that air intakes had double bends, sometimes triple bends with a drain hole at the bottom. Doors used a foam sealer, and exhaust was placed wall side. Farms are dirty places, if you're not dealing with feed dust, you're dealing with hay dust, or chemicals for plants, sprayers or livestock. There's always something that would ruin a machine quick.

The right enclosure

[plover]

NEMA rates enclosures for their ability to withstand harsh environments. Search for NEMA enclosures and pick the one that fits your machine.

Re:The right enclosure

[speederaser]

Search for NEMA enclosures and pick the one that fits your machine.

Here's one you might like but it's not cheap at $325 each.

Re:The right enclosure

[pelgv]

But that is an IP24 so it will not work for his application. So he needs IPX6 or greater (usually you will get IP66). Depending on what he means with "High pressure jet" it will be IP66 or IP65. Something like this: http://www.tteglobal.com.au/tt... And then he could use a fan inside with a heater exchanger, water to the outside and another heater exchanger with a fan outside. All sealed.

Re:The right enclosure

[petermgreen]

Theres more to it than that.

The problem is if you put something that makes lots of heat in a sealed box not much large than the item and don't make any provision to get the heat out of the box it's just going to overheat. So in addition to the sealed box you are going to have to find/build a cooling system that can collect the heat from the components on the inside and radiate it to the outside without compromising the seal on the box and without being compromised itself by the conditions outside. I would expect some sort of liquid cooling to be appropriate.

Given the wide outside temperature range and the wide range of heat output of a moden PC I'd think you'd also have to design something in to stop it getting too cold, maybe a valve to divert the coolant to an internal radiator if the temperature dropped too low and an explicit heater as a last ditch measure.

whatchadoin?

[jjeffries]

Can you give us curious folk a hint as to what you're doing?

Re:whatchadoin?

[Kohath]

Obviously he's building an army of robot football hooligans.

Start here...

[Anonymous Coward]

http://www.skbspecialtycases.com/

I deal with this kind of thing once in a while when deploying hardware in freezing conditions (down to about -60F), and the truth is there aren't many options that are as small as you want.

Headless?

[StevenMaurer]

This is the big question. Because, to riff off the 14 years old discussion, wireless has progressed leaps and bounds since then. So simply putting the PC inside a waterproof chest and using a combination of WiFi, Bluetooth, and a few wireless display technologies. This is what is presently on Intel's product roadmap anyway.

Your biggest problem is likely to be the monitor. Every means we have to produce significant amount of light (especially required for outdoor viewing), requires dissipation of heat. That means venting. Which means air holes. Which can get spray in it.

So really the question can't be answered unless you explain the purpose of the PC. Is it there to do things like take measurements? Can it be controlled from a mobile phone? (they're much easier to seal) This is what is needed to know how to give further advice.

Re:Headless?

[geekoid]

Not if you are using the gpu for number crunching and not display power.

Come on people. This is basic stuff.

Re:Headless?

[theraptor05]

He states that the GPU is for number crunching, presumably with CUDA or OpenCL or some such. While he doesn't mention if video output is required, my gut tells me no - if the computer will be in the path of a water jet, ther operator likely won't want or need to be there.

Re:There are computers built for this.

[OzPeter]

Yes, you can find off the shelf computers which will do this and which have real GPUs.

http://lmgtfy.com/?q=ruggedized+pc

That's not going to help him. Apparently where he is at, the google is broken.

industrial computers

[confused one]

You're going to have a hard time finding a high spec computer that meets your needs, because of the cooling requirement. If I were you, I'd look to industrial enclosures designed for water proof operation. (there are industrial computer enclosures) Make the system water cooled so that you can run cooling lines outside the enclosure and use an external pump and radiator; this will allow you to minimize the size of the enclosure containing the computer. You'll have to accommodate the VRMs and Southbridge, which are typically passively air cooled (but do require cooling). You might try taping off connectors and spraying the PCB with conformal coating, to reduce the damage should water get into the enclosure. Connectors can be filled with dielectric grease on the pin entry side and epoxy on the wire side to prevent water access there.

I have never tried to do this with a computer; although, the techniques above have been used by me in other applications.

Does the processing power need to be there?

[Anonymous Coward]

Why don't people provide more details when asking questions? Really, you'd think a bunch of IT related people would be sick of getting questions with vague details and thus be better at making their own questions.

Do you actually need a PC in that environment? Can you use a rugged wireless display/embedded system within reach of the jet, but connected wirelessly to the computer with the GPU that's in a safe location? This is probably the easiest and cheapest setup.

How to make a High-Spec PC Waterproof?

[lippydude]

Encase the PC in a fireproof rubber balloon like the ones used in Formula One and fill it with perfluorocarbon (PFC), then encase that in a rust-proof metal box.

Re:This seems the obvious solution

[geoskd]

Another idea which I like even better is to immerse the whole machine in mineral oil.

This is actually not that good of an idea. I ran a mineral oil rig back when I was in school, and the mineral oil dissolves the dielectric used in the "can" style capacitors used on almost all electronics. Over the space of about 3 years, the oil will destroy the exposed caps, and the machine will become flaky and ultimately stop working altogether. Also of note, the oil permeates and partially dissolves most silicone caulk and the plastics used for hot glue. Ultimately, its pretty nasty stuff in spite of appearing to be relatively inert.

Pelican Case + Thermostatic Heater

[localroger]

Double enclosed is best, but you probably don't have room for that. I've been putting stuff in food processing plants for 20+ years though where the conditions (especially during cleanup) are comparable. Find the smallest Pelican case (there are generic knockoffs, if you go with one check it thoroughly before trusting it) and equip it with a thermostatic heater to keep the temperature above 70F or so all the time to limit condensation. Pack in a big bag of dessicant because without double enclosure that still won't be perfect.

Re:Pelican Case + Thermostatic Heater

[NitsujTPU]

This is the correct answer. Another company is Otter Box. Build the whole thing, pop it in the case.

Another correct answer, do whatever heavy processing you're doing remotely and have this device just do IO and control. Stick a microcontroller in the box, so it generates less heat.

NEMA 4X is all you need?

[Anonymous Coward]

I'm used to IP67-IP68+(IE. IP69K) for my work in designing autonomous subs(although I have other experience from GPU mining bitcoins), but NEMA 4X is specifically designed for the high pressure water jet conditions you're describing.

Although I'm curious WTF you're doing in a mobile/stationary weatherized application that requires a GTX970(A Jetson TK1 is easier to cool and good enough for most computer vision problems)? I'll answer your question directly instead of asking you how I can back out of your difficult design requirements:

First off: Lets assume IP55 is good enough:
http://cosmotec.stulz.com/en/products/ventilation/kryos-filter-fans/
These are the most cost effective IP55 ventilation fans I've been able to find.

If that's good enough for you: get on McMaster and order a NEMA 4X enclosure and consider yourself lucky that was all you needed. You have an industrial cooling problem, they have industrial cooling solutions. If you want some a little closer to your side of the pond: request a catalog from Rittal or get on their website and see if they have anything that meets your needs.

If IP55 is not good enough, and nothing as generic as a cosmotec fan or a cooled Rittal enclosure can get the job done: you can start by reading all the other responses and see if anyone has a better suggestion I'm unfamiliar with. If not, your job is either impossible, no one here knows what the solution is(or isn't saying if they do), or you have to go custom. That means in house or out of house design.

First off lets make something clear: you have a thermal management problem, not a water ingress problem. It becomes a water ingress problem when you are unable to adequately manage your thermal output without circulating air from the outside of the enclosure.

Shedding the heat of a 500-1000W PC using nothing but convection cooling with the enclosure skin/fins is difficult in the size you've described so the easiest thing to do would be to cheat and exceed your volume constraints via an external radiator in a location where your volume constraints are less of a problem. Supposing that is not possible: in a stationary application the ground becomes a pretty good heat sink if you dig down far enough. An alluminum water block burried beneath your computer circulating water through a NEMA 4X enclosure on the surface with the CPU and GPU pimped out with watercooling blocks. Excluding that as a possibility(mobile application?): pumping the heat in to a thermally conductive chunk of material large enough to dissipate it is still your preferred solution.

If there is no way around self-contained: you're either going to have to spend a lot of time and energy maximizing the thermally conductive surface area(doing analysis to determine it is adequate to meet your use case a high enough percentage of the time to matter), make the system fail gracefully under the conditions where it exceeds it's thermal management capabilities, optimize system thermal efficiency to the greatest extent possible by doing things like underclocking the CPU and using more CUDA/OpenCL for your code, redesigning your system(using a wireless modem to offload the processing requirements to a datacenter like Amazon AWS or even a closet at a nearby facility), or some crazy combination of all of the above in appropriate proportions to maximize the value to the customer(whoever that is) on the time frame/capital investment scale they are willing to pay for, and/or manage their expectations appropriately to where you can redefine your requirements, and/or claim it's impossible and hope a smarter/more ambitious engineer doesn't prove you wrong.

The correct answer is so situation specific it is difficult to tell you what to do without more information. These are some of the questions I would ask. Good luck with your bizarre requirements definition. I'm sure you've been painted in to a corner for good reasons and not because of an unwillingness to compromise on the "I want everything" mentality that makes programs like the F35 and F22 so fucking expensive.

Re:NEMA 4X is all you need?

[jimwormold]

Thanks for the very informative answer and suggestions. In response to one of your questions about why I think I need such a high end graphics card, I need to do "real time" (ideally at 30fps) processing of 3D data. My current prototype (which isn't ingress protected in any way) runs at around 10-15fps, and with the GTX970, performance bottlenecks are no longer on the image processing side of things (uploading the images to the GPU now takes more time than the calculations), which they were using an older GTX650ti. Unfortunately, moving the data elsewhere for processing isn't an option - there is no guarantee of decent connectivity and the amount of data will be at least 25GB a day. It doesn't need to have a permanent display though, which makes life somewhat easier!

I can certainly make the box larger as you, and other slashdotters, suggest. In fact I've not "been" painted into a corner, I've painted myself into a corner and am always very happy to look for alternatives as you suggest. I'm a big fan of the keep-it-simple mentality! Ideally, an off the shelf solution would be perfect, but having talked to a few of the embedded pc manufacturers as well as endless googling, it seems that I'm going to have to design/build the solution myself. I very much appreciate your answer and clearly you have a thorough understanding of the types of issues I'm facing, and in a way I'm glad that I haven't missed something blindingly obvious!

I'm also realistic in that I don't expect the first prototype to work without hiccups, but if I can incorporate as many of the suggestions as possible in the design, then I can hopefully keep the failure/damage/rebuild rate as low as possible.

Thanks again for your post.

Re:NEMA 4X is all you need?

[adolf]

Hi. I have found the solution to your problem.

Longer wires. Put the box where the high-pressure water jet isn't.

You're welcome.

Re:NEMA 4X is all you need?

[Hognoxious]

Unfortunately, moving the data elsewhere for processing isn't an option - there is no guarantee of decent connectivity and the amount of data will be at least 25GB a day.

How are you planning to transfer it, Morse Code?

On gigabit ethernet that'd take a few minutes.

Re:NEMA 4X is all you need?

[Hognoxious]

Why, in that case, wouldn't you be able to put the "brain" out of the way of the jets? Don't car washes usually have some kind of booth/cabin where the operator sits?

Epoxy

[Anonymous Coward]

Many years ago, friend of mine was in army. He was in secret devision and one day they give to him a order: "Change the HDD of this PC" and they give to him new HDD, hammer and chisel.
He has surprised, because when open PC cover see massive block of epoxy. People before just fill the PC box with epoxy and made it fully water, shock and dust proof. Simple and reliable !
You must keep in mind that may be will have a problem with cooling of some staff like video card. You can do it with water block, if is not possible to cooling.

Re:Epoxy

[tippe]

Yeah, I don't buy it. There are so many things wrong with this story that make it implausible, the least of which is that epoxy-filled devices are not intended to ever be serviced, as it is nearly impossible to do so without damaging them even more.

Assuming that your friend was telling you the truth, I bet it's probably more a case of him falling prey to a form of "greenhorn" joke, similar to what an apprentice or new construction worker would have to endure on the job site until they proved themselves, like "get me a left-handed hammer" or "go get me a bucket of spots for the spot welder".

Re:Who needs a damn computer anymore?

[tlambert]

Joking aside, I wonder why the OP is putting the number crunching in the outdoor box rather then splitting the work between an embedded system for data gathering (or whatever) and off the shelf desktop for processing.

I expect all of the number crunching is being done by an on-board AI trying to figure out how the heck to get away from the high pressure water jet...

Re:This seems the obvious solution

[dgatwood]

http://www.liquipel.com/

They coat the chips in some sort of coating that insulates them.

My first inclination would be to get the biggest heat sink I could find, fasten it to the motherboard, and build a 12V to 5V and 3.3V DC-DC converter (and 1.8V, if needed). By not starting from 110VAC, you can cut the PSU heat to a level that might be manageable without fans. Then get extension cables for any connectors that you want to keep usable, along with a couple of heavy gauge wires for your 12V leads, stick the whole thing in a plastic box or bag with the cables hanging out the top, and fill it with epoxy....

Mind you, such an approach is almost certainly not advisable, but that would be my first inclination. :-D

Re:Doesn't seem too hard.

[Sarten-X]

Even if it cuts through metal, the simple solution is to just not put the computer in front of the jet. Like you said, put it in a box out of the way, with some baffles to stop water coming in the ducts, and just to be paranoid, elevate the computer within the box, so it's not sitting in a pool of any water that may come in.