12V DC regulation.

**480TURBO** · 04-15-2007, 05:36 PM

Hi all, a quick intro first! I built a car PC years ago when i was a student using an old desktop PC and a mastero 12v psu, it worked brilliantly and now ive graduated my budget allows for better stuff i'm building a better one!

Ive bought an epia m series mobo and a 12v dc morex psu. The input voltage on this is 11.6-12.6 volts DC so i cant run it straight off the 14v the car chucks out (horribly unregulated and full of spikes anyway!) I was thinking of using 3 12v 2A dc linear voltage regulator IC's wired in parallel to give me the required 6A that the board needs. I know i'll need good heatsinks and that linear voltage regs are inefficient but its the most simple way of doing it as far as i can see. However, the IC's need an input voltage of 15v dc which the car wont supply (i dont think, need to measure it!) So i'll have to run my IC's from a notebook step up voltage converter set to 16v or whatever.

Does anyone have any problems with this setup or ideas of a better way of doing it thats neater and cheap?

Thanks in advance!

**billmee** · 04-15-2007, 08:46 PM

Before I tell you to spend a hundred bucks on a Carnetix CNX-P1900....

Laptop PSU
You could do this with your laptop psu.
However you will waste a lot more power.
Your laptop psu better be rated to 8 or 9 amps (I'm ballparking here).

Regulator
An LT1038 is rated to 10 amps.
But be ready to provide a good heat sink and mounting location cause it's gonna get hot!
http://www.datasheetcatalog.com/data...0/LT1038.shtml
I haven't worked with them but search the posts they have been mentioned often.

Startup/shutdown control
You could make your own, based on the accessory signal and relays.
I've got one setup that relies on the taillight to isolate or energize the pc.

When you add up all the work you will have to do and the lack of features to going this route you should really consider a good DC-DC regulated 12v supply.

**MatrixPC** · 04-16-2007, 03:11 PM

You are almost in the same shoe as this guy. http://www.mp3car.com/vbulletin/powe...egulation.html
- You have an 12V regulated input PSU.
- You need to build a regulator for that PSU.

Since you already built a Mastero/Sproggy PSU, why not re-use the 12V rail of the PSU? I don't know what version you built, but the latest one 4.0-4.5 use National Chip to boost the supply voltage to 15V then regulated to 12V.
Follow the thread above and suggestion by evandude and me to build a 12V by-pass on that Morex PSU?

**480TURBO** · 04-19-2007, 02:35 PM

Cheers guys, ive already sold my old carpc so i cant reuse any of the parts from it.
I'm only running an epia board and a laptop HDD so power consumption should be minimal and well under 5A. I considered building a PSU but i'm lazy and busy and in the end found this:

http://cgi.ebay.co.uk/ws/eBayISAPI.d...8216%26fvi%3D1

I'll give it a bash and see how it works, if it cant supply enough current then i'll look into a dedicated carpc psu. I'm not too fussed about startup and shutdown controllers etc, i'd rather do it myself as i might not be using it on short journeys etc.