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Handling Systems Exposed to Extreme Temperatures?
NeoMagick asks: "I live in a rural town in the Pacific Northwest, and I'll soon be picking up a Shuttle system which will get mounted in the trunk of my car, and patched into probably an Alpine or Pyle in-dash LCD panel. This last week temperatures have gotten up to 105degF, and have been known to get to -10degF in the winters. I'm wondering if any /.ers have had issues with computers in cars in such extreme temperatures (overheating? freezing?), and if so what they did to solve such problems."
I work with hardware designed for extreme temperatures. As far as I can tell, these are the prime considerations.
1) Mechanical failure due to thermal expansion and contraction. This tends to affect connectors and plugs. Systems with poorly affixed memory components sometimes experience problems.
2) Dissipation of excess heat. A modest external temperature of 35C may produce a temperature in your trunk of over 45C. At 45C, the CPU will have a hard time dissipating heat since heat diffusion requires a gradient. CPUs may tend to fail around 55C.
3) Condensation. As you open and close the trunk in cooler weather, you'll be adding moisture to the closed space. Like dew, moisture will condense out of the air as components cool. Moisture on electronics tends to be less than optimal.
4) Vibration. Automobiles are notoriously hard on electrical components because of the constant vibration. Single strand wire tends to fatigue. Connectors shake loose. There are mounting methods for abating shock and vibration.
The systems we use for extreme temperatures do not sport contemporary CPUs because of the heat problems. To cope with condensation, we place desiccants inside the enclosures.
I have a PIII 600 in my car, and I live in Houston, so heat was a big issue in my design. Here's what I learned:
1) You MUST put everything heat sensitive in the trunk. The windows of your car act like a greenhouse, making the cab much hotter than the air outside. The trunk will usually be no hotter than the outside air
2) It helps not to have a black car.
3) Add as many fans as you can...and point them all blowing out of the case to try and reduce the pressure inside.
4) Check the operating temps on your CPU and Hard Drive. If they're not up to snuff, consider replacing them.
5) If you have a metal bottom in the trunk, you can use it as a heat sink. Just get a metal case and bolt it on there with some thermal paste between the joints. That metal will get fairly cool if you're going along at 70mph.
6) This is not a heat issue, but I'd recommend mounting your HD vertically. That way, when you hit a bump, the RW heads don't smack into the HD platter.
And if all else fails, buy a Peltier cooling unit and build a mini-air conditioner. I've never tried this (never had to) but it's my backup plan in case it ever gets too hot.
How exactly is this supposed to help when the car is not in operation? The poster above obviously doesn't live in a very cold climate.
I live in Montana. It's not unheard of (or even unexpected) to have a week of weather where we don't get above zero (Farenheight) during the winter. I remember one winter where I had a half inch of ice accumulation on the floor under the driver's feet because of the snow being tracked in and then not being able to get the car hot enough to melt it during the short drive to work each day.
-40 F is not uncommon to see during the winter months.
At that temperature, things don't like to work at all.
That said, if it were me, I'd probably just try it and see if I had any problems. If I had cold-related problems, I might consider adding some sort of very small resistive heater to the case and hook it up so when I plug in the block heater in, it also turns on.
I'm the tech guy for a Wireless ISP, and when we mount equipment outside, we generally will buy a box with a small resistive heater element and a thermostat in it to turn it on when the box gets below 50-60 or so.
The component most likely to complain about temperature and vibration is the hard drive.
:-/
/dev/zero > /dev/null, or whatever) to keep the motherboard components warm and well within design spec, which will help reduce condensation. Do the opposite on hot days - HLT the CPU when idle, so as not to make things any warmer than needed to get the job done, and take whatever other power-saving measures you can.
While your car's suspension will work rather well at isolating things from bumps in the road, it wouldn't hurt to get a little creative with mounting the drive. Suspending it between rubber straps might be a good idea, but watch out for things which are bouncy (resonant) -- it almost doesn't matter how much of the initial impact that your suspension absorbs, if it continues to shake the hell out of the thing several seconds after stuff should've come to a rest.
Hard drives come packed in open-cell foam, like a mattress pad, and seem to survive UPS Ground pretty well in such an arrangement. It wouldn't take too much creative engineering to fabricate an enclosure made predominately out of foam, but with a fan and enough room for air to circulate.
Temperature doesn't look like it's too much of a hassle, these days. I'm looking at the specs on an IBM 120GXP, which show it to be happy from -40 to 55 degrees celsius (-40 to 131 F). Since these are ambient temperatures, the drive is thus designed to withstand a trunk at 131 degrees with moderate airflow.
Since you'll be opening your windows and/or turning on the air conditioning Right Away on such blazing hot days, the hard drive should start recieving cooler ambient air at about the same time it starts generating appreciable heat of its own.
And in the winter, at -40, the last thing you're worried about is whether your hard drive will spin up. More important is whether or not the engine will, and if you'll be able to get the tires un-frozen from the ground. If you've got half a brain about you, you'll have the computer and stereo off, anyway, until the car is well under its own power...and, by that point, generating heat to warm up the electronics.
I'd avoid connecting the enclosure directly to the car's ductwork. Ever see a windshield fog up on the inside on a cold morning, just after you turn on the defroster? Imagine that happening to your in-car PC. Bad news.
Since the motherboard you've chosen is so bloody small, have you considered putting it under the front seat? Things would get impossibly tight in a sports car with power seats, but should be do-able in almost anything else. There's no reason for the box to be more than an inch or three high. Sescom is a company who makes a large variety of metal boxes for do-it-yourself projects - chances are, one of them would fit your motherboard, hard drive, and some manner of DC power supply justabout perfectly, while remaining small enough to slide under the seat.
Drill or punch holes in the sides of the box, and mount the biggest, lowest-RPM fan you can find on the top of the box, blowing down. You might even be able to do away with having a dedicated CPU fan, and get by with a just large heatsink.
There's a few other things you might want to look into, with software. There's a way to poll hard drive temperature using a protocol called SMART - if the drive is cold, keep it spun up to reduce the viscosity of the grease in its bearings. Likewise, if the drive is fairly warm, spin it down when not needed to reduce wear and help ward off data loss (they are, of course, -much- more durable with not spinning).
Do the same with the CPU, if it suits you. If it's cold out, run the CPU full-tilt (seti@home, some random busyloop, cat
The goal here is to bring the board to some desired operating temperature, and keep it there until the car turns off.
All that said, you'll probably find that the most sensitive component of your system is the LCD display, which will be painfully slow/frozen on cold mornings, and either solid white or black after a hot day of sitting in the sun...and there's really not much to be done about it, unfortunately.
good luck!
Kid-proof tablet..
on the other hand, if it could run with out the ignition being on, how fast would it drain the battery?
would there be any way to write a script that automaticly shuts down correcctly the system when you shut off the car. I know there are systems for turbos that do a simmilar thing. when you shut down a turbo automobile, especially if you have been driving hard, you are supposed to let the engine idle for 2-5 minutes before killing power. this is to let the hot oil out of the turbo and let every thing cool down properly. there aare turbo timers that continue to run your engine for a desired length of time without a key in the ignition, shutting it off for you. this lets you get out of your car and get on with your day without waiting around for your turbo.
could a similar system be adapted to shut down your automotive pc? how do people deal with this now?
i am interested in doing something similar now, and the shut down prodedure is my main concern.
I want 2D games back.