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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...
I'm thinking something along the lines of this:
http://www.tisch-env.com/pq200.html
People have already a put a lot of effort into building weather-proof, battery- and solar-powered cases which can hang on telephone poles for applications such as environmental monitoring. They hang them along highways (some of them have a hook on top to hang from a telephone pole and come with a big forked stick to facilitate getting them down from the pole), then you come back in a month to check what sort of pollution is being produced. Don't reinvent the wheel here, talk to one of those companies and see about getting some cases, maybe with power supplies included but without the environmental equipment.
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Michael Sims-michael at slashdot.org
Here's an idea - use one of the embedded versions of Linux to run an ultra-small server - (/. has run several articles on this including one about the Worlds Smallest Server) - and use a standard industrial box to enclose the whole thing. Digi-Key or Resource Electronics or just about anybody has those.
Since we're talking about a wireless network you're probably not going to get off cheap but you can almost certainly manage to produce something stable and with a long up-time that's affordable.
"Bah!" - Dogbert
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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Time is Nature's way of keeping everything from happening at once... the bitch.
duct tape. Lotsa duct tape.
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.
Environmental Specs:
...additional info here...there are also different units available...
Operating Temperature: 0 to 50 degrees C (32 to 122 deg. F)
Non-operating Temperature: 0 to 60 degrees C (32 to 140 deg. F)
Shipping Temperature: -40 to 60 degrees C (-40 to 140 deg. F)
Relative Humidity: 5 to 95% non-condensing
Wet Bulb: 29.4 degrees C (85 deg. F)
Altitude (operating): 0 to 7000 feet (0 to 2134 meters)
(non-operating): 0 to 15000 feet (0 to 4575 meters)
Electrical - 100-125VAC and 200-245VAC switchable
BTU Output (as-shipped): 200 BTU/hour
(maximum config.): 1417 BTU/hour)
Shock: 30G, 3ms duration
Vibration: 0.67G RMS random from 5Hz to 500Hz
Particulate Protection: Dust and dripping water resistant -
We used to use a similar types of machines as data collection units for slot machines. The PC's ran 24/7, year in and year out, in poorly ventilated cabinets in an incredibly dusty and dirty area--no moisture to deal with though... Very reliable. The question is will the machine generate enough BTU's (in the spec) to keep it warm during the winter...and will it stay cool enough during the summer.
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
- Dan
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.
While saving a few bucks is admirable, the simple truth is that the wavelan access points were already designed to solve all of these problems and more.
If you're doing something that's non-profit (or otherwise capable of generating good PR for Lucent), give them a call and see if you can get a discount.
Otherwise, you're going to end up spending more money in the long-term on maintainence and replacement (like someone said, PCs on a phone pole would be a tempting theft target) that you would on the more expensive equipment.
Forward, retransmit, or republish anything I say here. Just don't misquote me.
We do a lot of utility work... in the sort of places no one really wants to think about (under New York City) We don't use traditional PCs, but we do use traditional pc parts (or at least traditional boards, usually with a few specailty boards. You could probably mount traditional pc parts (including the power supply) in one of the industrial cases we use - with the understanding of a couple of things... you can't run a hot processor, you have to have massive heat sinks and it takes a lot of testing and time to do it right... Think "low-end Linux box" not "quake machine."
The cases (er cabinets) we buy are pretty darn rugged (i.e. waterproof, very heat resistant, pretty resistant to shock, etc).
Now keep in mind, all external openings (for cords and etc) need to be tapped and all internal components need to be mounted in some way.
Well here's a plug for the people we buy from:
Contact information
Stahlin Fiberglass (a Division of ROBROY Industries)
Belding Division
Belding, Michigan 48809
Phone (616)794-0700
However, that's just for a PC... I hadn't even considered a monitor. If you're expecting to put in a monitor and stuff like that... it gets a lot more expensive and difficult... now what you're talking is purchasing industrial grade PCs...
Now you might be talking purchasing something from Xycom Automation. But, most of these are also flat/touchscreens ($$cha-ching$$) and once again come preloaded with DOS/95/NT. I don't know about Linux drivers for those... However if you look around enough you will find a lot of machinery does run with some form of *NIX (to avoid the reliability problems of MS)
Well, that's about the best I can do for you...
You say you want a revolution?
We use the Super Duty laptop cases sold by cases-cases to lug around our laptops in a marine environment. They definately hold up to abuse, and are comletely air/water tight.
This would be more of a "you like, uhh, put your PC into this box thing" kind of a solution, and it will probably be a little bulky. You would still have to look at temperature, and lightning problems (plastic case tho, so it might be ok).