Putting a computer in a car

[Claudius]

Basically, I want to build a barebones system for the sole purpose of playing my whole mp3 collection in my car.

Does this sound feasable?

Some problems immediately arise in my mind. For instance: power. I'll have to do away with the power supply and run the computer off the car power (12v dc). Creating the positive voltages and the ground shouldn't be a problem. Creating the negative voltages seems impossible with a car though. Are the negative voltages really necessary?

So what do you guys think?
Can this be done?
Will the computer survive a car ride?
Is a car powerful enough to power a computer?

Claudius

[Aedan]

Yes, it's feasable

The problem you have with power isn't generating the negative voltages - that's actually pretty easy... It's stopping all those transient voltage spikes from eating the electronics! Most car systems actually run at about 14V whilst the car is running, 12V when the car isn't, and 8-10V when you're trying to start the car.
Things like ignition systems can punch pretty large voltage spikes onto the car power system (>20v on some cars!).

You'll also need to build a mount that'll prevent the hard disk from suffering damage from vibration and shock from the road.

If you want a really small unit, look at some of the SBC (Single Board Computers) out there. Advantech are one such manufacturer. One of their NS Geode powered systems could be attached to the bottom of a 3.5" hard disk. If you need more power, you'd need a larger board (5.25" inch - same footprint as a CD-ROM drive, without the height)

The SBCs generally only need a +5V supply, making the power supply even simpler, if you use a laptop hard disk, as they only need a 5V power supply. Some of the SBCs come with onboard video (LCD/VGA), onboard audio, CompactFlash support and onboard Ethernet - not bad for something that's the same size as a floppy drive!

If you decide to go with standard PC parts, you'll need a power supply that can provide 12v, 5v and 3.3v at an appropriate amount of power. Depending on the soundcard you use, you might also need one of the negative voltages.

There's two ways of generating the power. The easiest way is to use an inverter to convert the 12v into mains, and then have the mains fed into a standard PC PSU. It's ugly, it's a kludge, but it's simple and works.

The second choice is more difficult - getting hold of/building a power supply that converts from the car's 12-14v into controlled power for the PC.

It's entirely possible - a car has plenty of power for a computer, multiple times over! Mounted properly, a computer will survive in a car no problem.

Good luck,

AidanII

[Jazz]

Use laptop drives if possible i know its more expensive but they take much much more shock.

[Claudius]

Wow, Thanks for the advice, I didn't even think of SBC's.

Keeping the voltage's stable shouldn't be a problem by using zener diodes. Even a sharp voltage spike shouldn't phase it. I risk losing power at lower voltage levels, though, since I will have to blatantly divide the 12V to get to them.

What about connecting a PSU directly to the car's alternator? That solves problems with power loss and it can provide negative voltages.
Thats probably a bad idea though. I'll stick with the voltage division.

Claudius

[dimmreaper]

I like this guys approach, http://neon.mp3car.com/index.html ,It solves the display problem quite cleverly.

[mrpcman]

I ran a power inverter from ratshack for mine..pretty easy.

[The Spyder]

A friend of mine is throwing togerthere a system too- P 233- Nic- 40gig hd- S3 Video- and usch- threw it all together w/ an touch pad LCD screen in the dash- works fine- used a 200w inverter from outrageouse audio-
Spyder

[robbie]

Ya know OC.com had a thing on this about a year or two ago. Try there site and a search.

Hope this helps.

Rob

[Azriel]

If it's just for mp3, go with the itty bitty via/cyrix sub flex board. It has a soldered down C3. The are by no means fast, but it would have no problem with MP3. You should stuff a video card with TV out in the PCI slot, and use one of those tiny color LCD TV's from http://www.allelectronics.com/cgi-bi...-50&type=store

Not cheap, but sooooo simple.

There's even a TV-out fullscreen plugin for winamp.

[Aedan]

Originally posted by Claudius
Keeping the voltage's stable shouldn't be a problem by using zener diodes. Even a sharp voltage spike shouldn't phase it. I risk losing power at lower voltage levels, though, since I will have to blatantly divide the 12V to get to them.

What about connecting a PSU directly to the car's alternator? That solves problems with power loss and it can provide negative voltages. Thats probably a bad idea though. I'll stick with the voltage division.

Depending on how noisy the ignition system is, I'd suggest filtering the 14v line heavily to absorb the worst of the spikes.

Given that some SBCs only need 5V, you could probably get away with building a simple switcher - there's some integrated step down switchers out there that would probably work very well for your application. That'll mean you don't need so much cooling as switchers are far more efficent compared to linears.

AidanII

[Kaitain]

The people to talk to about supplying power to electronics in a car are auto hi-fi specialists: places such as this one have been supplying heavily filtered power supplies for years, as people with more money than sense try to deafen themselves in ever more cruel and unusual ways

Given a high-power filtered DC supply, it's not too much of a problem to step this up or down to whatever voltages you want.

[Azriel]

Would it help to put car-audio stiffening capacitors before the regulators? They could take up whatever excess the reg can't handle, and use it durring sags. Would also probably be enough to give you a minute to shut it down after the ignition is off.

[Claudius]

Originally posted by AidanII


Given that some SBCs only need 5V, you could probably get away with building a simple switcher - there's some integrated step down switchers out there that would probably work very well for your application. That'll mean you don't need so much cooling as switchers are far more efficent compared to linears.

AidanII

What is a switcher exactly?

[Azriel]

A switching regulator.

[mrpcman]

Originally posted by AidanII


Depending on how noisy the ignition system is, I'd suggest filtering the 14v line heavily to absorb the worst of the spikes.

Given that some SBCs only need 5V, you could probably get away with building a simple switcher - there's some integrated step down switchers out there that would probably work very well for your application. That'll mean you don't need so much cooling as switchers are far more efficent compared to linears.

AidanII

doesn't a typic inverter do a good job of absorbing spikes?

[Azriel]

I think Aidan is going for the less "duct tape and bubble gum" aproach. Yes, if you have an extra cubic foot of space to throw at the prodject, you could very easily use an inverter, a small ups, and a PSU. Due to space issues, I think Aidan's method is better. I'm not sure but I think what he's getting at is to regulate the 12v, and patch into a PSU after the transformer, using the existing components to get all of those different voltages needed for ATX power.

(I am not sure that 12v is what comes out of the transformer in a PSU. This is conjecture. If anyone "knows" please speak up. I have no multimeter.)

[mrpcman]

Originally posted by Azriel
I think Aidan is going for the less "duct tape and bubble gum" aproach. Yes, if you have an extra cubic foot of space to throw at the prodject, you could very easily use an inverter, a small ups, and a PSU. Due to space issues, I think Aidan's method is better. I'm not sure but I think what he's getting at is to regulate the 12v, and patch into a PSU after the transformer, using the existing components to get all of those different voltages needed for ATX power.

(I am not sure that 12v is what comes out of the transformer in a PSU. This is conjecture. If anyone "knows" please speak up. I have no multimeter.)

oh, alright, but my inverter is only like 3x6x1, so i don't have much of a space problem.

[Aedan]

Originally posted by Azriel
I think Aidan is going for the less "duct tape and bubble gum" aproach. Yes, if you have an extra cubic foot of space to throw at the prodject, you could very easily use an inverter, a small ups, and a PSU. Due to space issues, I think Aidan's method is better. I'm not sure but I think what he's getting at is to regulate the 12v, and patch into a PSU after the transformer, using the existing components to get all of those different voltages needed for ATX power.

(I am not sure that 12v is what comes out of the transformer in a PSU. This is conjecture. If anyone "knows" please speak up. I have no multimeter.)

Yeah, I was going for the no duct tape and bubble gum approach. This was based on the fact that most SBCs, coupled with a 2.5inch IDE drive only require +5V. No other voltages. If you use such a solution, then you only need a regulator that'll take the 14V and bring it down to 5V. Given that most SBCs need a good few amps to start up, then a switching regulator makes more sense.

I was trying to avoid the mess of haivng to have an ATX PSU and all the junk that goes with that. The easiest to implement solution would use an inverter and a standard ATX PSU, rather than what I'm suggesting.

AidanII

[Claudius]

I am unfamiliar with what a switching regulator is.
Can someone explain?

[Azriel]

Aidan, how fast would you figure an SBC would need to be to play MP3's well? I know P-100 laptops suck at it.