Homemade "carputer" power supply?

Just wondering....
Could a viable solution for a homemade carputer power supply be a very simple setup, such as a cheapo inverter connected directly to the battery/alternator lines, with maybe one of those big capacitors to help with spikes?
I know that a professional "carputer" costs MEGAbucks, which I don't have so I thought I might be able to just hardwire an inverter in and put a normal, desktop computer(minus the 50-lb CRT monitor ) in the back of my camper-covered truck... I would also have one of those cool LCD monitors on a swivel on the dash.... Ghetto, huh?
Anyways, I want to know about the output variations from an inverter (NOT one of those thousand-buck "prosine" ones either, more like $200 MAX...) It would be just to power a 350W or so computer... nothing fancy... And I'm fairly sure that I could find an LCD monitor, 10" or 12", that runs on 12V without the need to invert its input.
The variations that such an inverter would put into the input line would not concern me, as I own a pre-ECM '82 Ford F150....
I just want to know about the input amperage needed and the output sine wave, as I don't have an oscilliscope
Also, I would like to know about DC-DC ATX power supplies, as those would be the best solution.... But the only ones I could find for 12V were only 250W and were relatively expensive... Does anyone know any links for these?
Thanks for any help!

Most good inverters will give a stepped sine wave output; the more steps, the better. Watch out for square wave output ones -- those are cheaper, but don't work with computers. Make sure your alternator can put out enough power for your computer.

Keep in mind that the output from your alternator isn't exactly 12 volts. More likely, it's in the 13v to 15v range.

Yeah--I was thinking about putting it on the regulator side of the circuit.... But it shouldn't hurt a good inverter to have a higher input power, would it?

If you connect it directly to your battery, it will drain your battery . . . Make sure it shuts off when the car shuts off.

Z

yeah - as zach said - treat the computer like leaving your
full headlights on.

This is where using a Via would be a good idea - much lower
power consumption. - and think about laptop hard-drives

Damn me for not saying that first!

A Via Epia-based computer (C3) would be perfect for this application. As I can't really picture somebody doing anything too computationally intensive on a carputer, I think the C3 would work great in a car. Because the trunk (or bed of your truck, in this case) will get quite hot in the summer, you're going to really NEED a cool-running processor if it's air cooled. Ambient temps might well be near 100 depending on where you live, and you need to keep that in mind. If a C3 can run fanless, it will certainly run with a fan in 100F ambient temps. And it will consume far less power than anything I can think of (does a C3 beat the new Pentium M as the low voltage king?).

And I think a computer (at least one running more than a C3) will draw for power than, say, headlights. If you can run it from a cigarette lighter, all the better (not that you should actually do it, but I think it might be wise to be able to do it).

Z

If I actually did this, I would want a computer that could actually do something like play a fairly good game every once in a while just for bragging rights Of course, I had thought about that little heat problem, and was thinking about making blowholes of sorts in the camper cover Maybe controlled by thermal switches on an independent battery, with the charger for that, the monitor, and the inverter on a high-amperage relay connected to the ignition and maybe a relay override switch too.. a 3-position switch--ignition controlled, on, and off... You get the idea...

If you can somehow tap into the air conditioning system and duct some of the air into the case, I woulr recomend doing so. Certainly you won't want hoses in your cab, but if you get to it and route the hose around and into the bed area, I think it might almost be necessary. I can't imagine how else you'd be able to keep it cool. Moving stale air won't help if it's baking under the sun. You need a source of cool air. If you can't tap the A/C, then you might find a way to duct outside air (filtered, of course) so that you get good airflow while moving. You might not be able to run the computer while stopped, but I doubt you'll overcome the heat limitations without some sort of ducting. I can't think of anything else that would work. If you want a high powered system, I'd go with either a P4 or a PIII. Each of those has better thermal properties than the Athlon, and are lower powered (I believe, anyway).

Z

Unfortunately my a/c is broken and this still wouldn't help when the truck is off, baking in the sun.... Good idea though, and worth a thought if I ever get my A/C fixed. My mom's boyfriend is a commercial refrigeration contractor for grocery stores, so I'll see if I can sucker him into looking at it

I honestly don't believe you can get a computer to work in that environment without A/C. And it should be off when the truck is off, so it shouldn't matter how hot it gets when the truck is off. You just need to delay the power-on for the PC until the A/C gets cold.

Z

I would be running with the windows down anyways since the AC doesn't work, and I could just open the little passthrough windows.
I'm not worried about temps while the truck is running, but rather while it is stopped.. I seem to remember reading somewhere that temps can reach 140F (60C--I think) in a car with the windows rolled up. However, it would probably be much less as the camper shell is fiberglass and has only 2 small side windows to let the sun in, so it might be ok, but I'm not sure about storage temps for various components...and it would be rather cold in the winter too..

don't let any of us put you off n17ikh - just keep us informed
, and we'll all try to help with any problems you encounter.

Now if you lived in my home town - just keep the water off
the board will keep it cool enough

It doesn't matter about any of this right now--I don't have any money anyways But these are all good ideas... Maybe when I'm 16 and can get a job...

You might consider making the whole bit portable and make a docking station-like contraption, that way you can remove it during inclement weather.

Z

Good idea. Actually, I was going to build a wooden frame and shock-mount it with either recliner springs or bungee cords... But I could make it slide right out of the wooden frame...

Not sure where to get them, but Channel Well has a 300w dc-dc unit in either 24v or 48v inputs. Website is www.cwt.com.tw

just get a new 400 watt for that extra juice

That's not a good idea

Actually... I might change my thinking on this and move this thread to Alternative Mods, that's where it really belongs.
Another solution for the PC would be to get a Shuttle and just put it in the middle of the bench seat... This is currently my best option for this idea, as the Shuttle could be easily moved and I could just use a few minor case mods to make a sort of "docking station" to make it easily removeable from the truck.. Also, it would be easier to keep cool in the summer/warm in the winter, plus it would save me from cutting holes in the truck bed and the wiring would be easier...

I was googlin' and found this...
http://www.keypower.com/proddetail.asp?category=DC-DC+Power+Supply&subcategory=12VDC&linenumber=15
It's a 250 Watt 12 VDC power supply... Could that power, say, a 2Ghz or so p4? and, also, could this fit in this case>>
http://www.svc.com/amsgbp4albas.html
If it can, then I just found a great solution to the inverter problem...

Edit-> Also, www.displaze.com has some 12 V LCD displays that would work... specifically this one http://www.displaze.com/Html/Products/Chassis/Z181a.htm I could just bypass the inverter altogether... But is that price $38.59, $385.90, or $3859? It makes no sense... $38.59 is way too cheap and $3859 is way too much, so I guess it's $385.90...

Also, the power consumption of the monitor and power supply is 41A @ 12V... Not sure about the alternator of the truck, but I think that it's more than powerful enough.... I can't find my repair manual...