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I recently got an otterbox drybox for my phone. I was sitting and thinking that its waterproof, crushproof, and big enough to fit what I need as well protective foam. I realized this would make an amazing project enclosure...

My only problem is that I can't get the wires out of the box without negating the waterproof aspect of the box. I was thinking to drill appropriately sized holes in the box, insert bolt style contacts, and seal it with a mix of silicone caulk and gorilla glue but im not sure if the mixture would be conductive...

normally I would just go with the idea but I figured I would ask if anyone has had this problem and solved it. I want it to still be water proof up to 100ft and crush proof up to 1000lbs and I'm not sure if iv got the right idea...

QUESTION: How do I seal a project enclosure to be water and air tight using a NON-CONDUCTIVE seal that can withstand greater forces than a grommet?

PS: if off topic please vote to migrate, don't just down vote please

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A hot glue gun works perfect and hot glue does not conduct. –  deathismyfriend Aug 30 at 0:09
    
Hot glue will make your gear friends with deathismyfriend's friend. –  Russell McMahon Aug 30 at 7:27
    
Pressure per area on wires has to be higher than pressure to be resisted. As well as issue of conformally fitting seal to the wires - if you are using a compression fitting then pressure of compression / area has to exceed psi differential. It can be hard to get enough clamping pressure over a large area. Consider running solid conductors through eg a circular panel with eg solder buckets both sides and seal those with a surface bonding sealer of choice. THEN seal the panel onto the housing using o ring seal and any of the available bonding methods. eg an O ring & panel clamped by Seelskrews –  Russell McMahon Aug 30 at 13:42

6 Answers 6

I think what you're looking for is a "bulkhead connector". You want this enclosure to withstand 100' water depth, though? Without pressure compensation? You're asking a lot! You may have to opt for a spherical enclosure instead - the flattish sides of the OtterBox aren't likely to be able to withstand that sort of pressure differential.

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I suppose 100ft is a bit much. it's what the box is advertised to be able to withstand. same with 1000 lbs... –  Konner Rasmussen Aug 29 at 15:54
    
thanks... now I have to find where to get one as radioshack doesnt have them –  Konner Rasmussen Aug 29 at 15:59
    
@KonnerRasmussen - a good thing, too; I couldn't trust a Radio Shack bulkhead connector for that sort of pressure if they did carry them; you'll need something pretty robust, with a really excellent external seal. 100' of water is more than 43psi, which is more pressure than your car tires should be expected to handle. –  TDHofstetter Aug 29 at 16:07

As already mentioned, 100 ft is a lot. IEC 60529, which is a standard for ingress protection, tests their IP67 rating at 1 meter depth for 1 hour. IP67 is generally considered to be equivalent to a NEMA 6 enclosure, I think.

There are a number of companies that make multi-hole, water-tight cord grips. Two examples that come to mind are Heyco (IP68) and Sealcon (IP66/IP68). There are other companies that make similar things, too, so look around.

One thing to keep in mind is that if your lead wire exiting the box is stranded, you have a leak path through the wire (between the insulation and the copper strands). One solution to this is lead wire manufacturers can fill that space between the insulation and copper to prevent leaking. Another option is to have a water-tight connector on the other end of your lead wires, too.

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You could use waterproof connectors, but they can get quite expensive by the time you buy the mating pair.

Your idea of penetrating the enclosure with fasteners used for contacts is a good one if the electrical conductivity of whatever they're submerged in doesn't matter, and you can do it all with seelskrews and no glue.

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My approach to the problem would be to do an end run around passing signals & power through the wall since, as others pointed out, 100' is pretty darn deep and a lot of pressure.

To send/receive data, use a transparent/translucent box and communicate with the outside world through infrared. Signals can be sampled and transmitted via LED/photodiode. Loss won't be an issue if the receiver and transmitter are immediately on either side of the enclosure wall.

Supplying power is a bit more difficult, but you should be able to inductively couple through 0.1" of plastic without much loss.

But if you're looking for a cheap, watertight material to make small enclosures, I'd start with PVC pipe and plumbing fixtures.

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I like the idea, but I already thought of that. I intend to use an android cellphone running code to control an io board... the thing costs 50 buck and android phones arent cheap either. I really want this so the main expense is protected. Im making a multipurpose control unit for remotely controlled anything. I intend to start with an rc quad rotor helicopter... anyways, I want nothing but motors, wire, and plastic to be outside of the box –  Konner Rasmussen Aug 30 at 6:10

Depending on what sort of connections you'll need in or out of the box, you can use standard panel connectors or feed-throughs and cement them in. Provided the pin connections are solid (not hollow) and you use good strength epoxy, the result should hold up pretty well, although I'm not running the allowances for pressure at 100ft depth in my head.

If you need a more generic connection where it won't suffice to use something like an Ethernet or USB panel, then you may want to check out if you can find a supply of MIL-DTL-38999 connectors. These are round panel connectors, circular, high pin density, and the -38999 standard deals with connectors for harsh environments, namely swamp and water and the good stuff. These connectors lock via an outside screw mechanism.

Granted, they're filthy expensive but you get a large amount of pins that can be used for anything from bit-banging to GPIO to more advanced protocols.

You can find a more generic list on DigiKey of -38999 connectors here. To find out what they're rated for in terms of exposure you might want to consult the standard of which the closest link I can find is here.

Comment on this and let me know what you're looking for specifically and I can suggest options that are less likely to make your wallet (and wife, if applicable) hate you.

EDIT: Also, don't mix caulk and Gorilla glue, as the mixture/resultant slurry may not hold. Use one or the other, and a hard epoxy or the Gorilla glue is most likely the preferable route. Keep in mind that Gorilla glue has a tendency to foam up when it's curing so take that into consideration if attempting to work in tight spaces or tolerances.

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im trying to make an all purpose control unit for unmanned vehicles... im starting with a simple quad rotor helicopter but would like to make unmanned aquatic vehicles at some point. I would like to have a unified enclosure that can just be switched from "ModelXXX" to "ModelXXX" mode on a software level and be reused... It would also make them REALLY easy to repair and thus insure... I currently have an "otterbox pusuit 40" dry box but hope to work with the "otterbox 3000/3500" at some point... and thanks for the tips with the glue, good to know =) –  Konner Rasmussen Aug 30 at 6:19
    
Ah. A DIY submersible. Well, you'll have to give me a little bit to come up with some better ideas, but the -38999 connectors are pretty generic (that is, they aren't like Ethernet lines that are typically only used for Ethernet), so you're always free to repurpose them later. If price is an issue (I understand they're expensive), I'll look into other "weatherproof"-type connectors. –  blasthash Aug 30 at 6:29
    
35 - 50 dollars isnt too bad, considering that something like this, fully assemmbled, goes for about 2500... how exactly go those connections work? will they function for a set of <= 12v connections? (which would be used to control the motors) –  Konner Rasmussen Aug 30 at 7:56
    
These connectors will tolerate 12V. Many of them are designed for aerospace and so you can better believe they're designed to bus some good power. The question is how much current you'll need. You might want to find the Amphenol datasheet to look for that. Worst comes to worst, you can take away one I/O line to double up for current consideration's sake. –  blasthash Aug 30 at 8:39

if you use it in sea water you can use goldplated contacts for the pins in the housing. (they will not oxidize like most others will) and you can use some strong magnets in the housing to make it easy to click the cable side on. (that side then need to have some iron our magnets with the right pole to the encloser side)

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