Outdoor Computer Cases?

danci asks: "I'm building a wireless network in a local community using Wavelan/IEEE cards. I'd like to avoid purchasing Wavelan access point so I'll try to use Linux instead. So I'd like to build some rather small but robust machines that should be able to survive summer, winter, snow, rain and most other weather conditions while being mounted on the antenna mast (or at least as near as possible - cable length heavily decreases range). So I guess what I wanna know is whether there are any weather proof, computer (PC) cases available out there. Or some other, low-cost solution (don't want to build a house around all that)." This would be too cool. Just imagine, a series of computers mounted to telephone poles with wireless network cards...

Comments

Some questions about the application

[Tau Zero]

I'm not sure why you need to put the computer out on the mast. Care to explain that (other than it being cheaper to have one case than two cases), danci?

My point: GHz RF has high losses in cables, but typical data rates have much more managable losses. If you can split the RF sections from the rest of the system, you can still put the electronics in a temperature-controlled environment while keeping the antenna cable short. (This assumes that the RF section will function under temperature extremes, which it may not. Test things in an environment chamber before you rely on them.)

I'm not familiar with Wavelan cards, but I'm going to make a guess here that they have both the digital and the RF sections on a single internal bus card and you don't have the option of splitting the system. In this case I would examine better transmission lines. One old technology I'm aware of is Goubeau line (I think that spelling is correct, Georg Goubeau is listed as being on the faculty at the University of Jena in Germany, specializing in the generation and propagation of EM waves). Goubeau line uses a pair of "launchers" to take a signal propagating on a coaxial cable and allow it to travel in the neighborhood of a bare wire; this nearly eliminates dielectric losses. While you'd need coax for any runs indoors, you could use Goubeau line to go from the outside wall wall to the top of your mast. I'd suggest using a flexible standoff/tensioner on the mast to keep the wire taut, and avoid the use of spacers. If you have a tower, I'd try running the line right up the middle.

Niggling issues like dealing with icing always rear their ugly heads. You may wish to design your antenna so that it is always at DC ground and have a big honking transformer to throw some low-voltage AC up and down your wire. This would let you melt ice and snow off it. If the Wavelan card provides signal-quality reporting you could even have your computer operate the heater as needed.

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There are lots of factors to consider

[BobTheTomato]

Finding all weather sealed computer cases are the least of your concerns. They are fairly easy to find, especially if you decide to use a SBC instead of a traditional AT or ATX motherboard. (The slot covers are very difficult to seal on AT/ATX). Do a web search on SBC to find a plethora of single board computer manufacturers. You will probably want to get something in a PC/104+ form factor instead of a backplane based form factor.

Look into the D38999 series of mil-spec connectors for bringing connections out of the box.

http://www.amphenol-aerospace.com/DEFAULT.HTM

Don't forget to chose your components wisely. Get industrial temperature range (-40 to 80C) components where possible, and especially if you intend to use a traditional hard drive. A flash drive is better if you can afford it. Spinning up a mechanical drive when it is too cold can destroy it.

Finally, put some thought into heat dissapation. For outdoor applications it is best to have a sealed box, which means no cooling fans. If you can, choose a low power consumption motherboard. (say a recent 486 class machine.) By all means, get a case that has large cooling fins on it, as that is the ONLY way that you'll ever get heat out of the box.

Good luck.

Outdoor cases

[reaper]

I think I can help you.

I'm currently working on an outdoor pc system designed to basically work in man holes (15 feet fully submersible for prolonged periods, dust/water proof). What you need (and this is only one solution, but it is cheap) is a single board computer, power supply, NEMA 4 rated enclosure, and applicable glands to bring the wires out. Basically you mount everything inside your box (generally made from fiberglass, aluminum or some type of plastic), install the glands (watertight cable feed throughs), and mount this baby.

JumpTec has some of the systems you could use, and more importantly has an IDE flash disk that makes all this easy to do without a hard disk. Also Win Systems is a pretty popular place to get PC/104 embedded systems.

As for the case, Hoffman has all the enclosures you could ever need (unless you're working in man holes).

Some people have recomended Dolche, but I'd avoid them as they are way expensive. More useful for interactive systems.

good luck

NEMA enclosures

[SEWilco]

I think what you want are called "NEMA enclosures" in the industrial environment. Sealed boxes. You pick a level suitable for an outdoor wet/freezing location.

Parvus has several for the PC/104 size, as does Tri-M. Digital has some for their products.

There are plenty of generic NEMA enclosures available, up to walk-in size.

Remember you may need a heater or cooler. There are standalone devices, although I also have seen one PC/104 card with thermostats.