PSU Requirements

**Base** · 09-30-2008, 06:44 PM

Hi there,

Bit of a question that I hope you will be able to help me with..

I want to setup an in car pc.. (obviously.. Otherwise I wouldn't be here..)

I have a number of questions that I have desperately tried to get answers to, on google and on here, but just don't seem to be able to get the answers I need.

Hardware:
- I am planning to run an Asus EEE Box, a 7" TFT Flat panel display & a GPS unit. I know that the Asus EEPC draws a little under 20 Watts of power on maximum draw, but I am not sure of the following. Do I power the Screen, PC & External HDD from the one in-car PSU. If so what kind of PSU do I need? I am guessing something 300W+.
- Will my TFT require the same kind of stable voltage that the PC does? If not then can I power it directly from the battery?
Software:
- I have been searching (to no avail) for a really good in-car PC suite. Something that plays Music, Video's & support GPS.
- I know that I can go online and find some random free GPS software. But I like the "fine tuned" interface that suites like TomTom and Garmin do. I know that Garmin do a laptop GPS software suite but I can't find where to get UK maps for it?!?
Power!!!
- I know the Asus EEE Box uses a 19V adapter to power itself, however my car battery is 12V. Does that present problems? Can I draw 19V from the battery over a long period of time without damaging it?
Shutdown & Startup
- I want to have button on the old dash board that will only provide power to the PC when I press it. now this is pretty easy, just a rocker switch interrupting the + or - voltage to the PSU. However I want to be able to change how long the PC stays on for on the fly. So say if I was "CruZin" with the "Fellas" and decided to "Pump-it-up" and get some "CHOOnEZ" on (if I decided to use the PC when I didn't have the engine on basically) is there anything I can do/buy to allow me to change how Long it stays on for? Would a permanent switch be a good thing? Just to literally have a on off button, that would act separately to everything else? Also can I buy a box that gives the PC a nice shutdown after I turn off the car engine?

My apologies if I have confused you.. Everything is in my head, just trying to get it down onto the keyboard is another thing entirely!

Any help would be sincerely appreciated..

Cheers

Tom

**FusionFanatic** · 10-01-2008, 11:56 AM

1.) 300w??? you don't need anything that powerful for your proposed system. your EEE-box consumes 20w, your monitor will consume about ~10w, and your external [3.5"?] HDD will consume about ~24w (a 2.5" laptop drive will consume even less). that's about 54w total power consumption. and yes they all need regulated power (stable voltages) and can all be powered from a single carPSU.

2.) I don't know of any "in car PC suite", period... what the vast majority of us use is called a front end. it's basically an easy to use 'face' over windows. personally, I use RoadRunner (it's free), it plays music through winamp, videos through WMP, and I use iGuidance4.0 for GPS (all are embedded into roadrunner).

3.) no, that doesn't present problems, but it does limit your PSU options. Carnetix makes a couple PSU models that can output the ~19v your EEE box requires, and they have secondary 12v outputs to power your HDD and monitor (with an optional 5v 'add-on' output).

4.) you can wire a switch if you want, but you don't want it to interrupt the power to the PSU. car PSUs wire up like an amplifier, they have an 'always live' constant power and ground connection, and a IGN wire to connect to your ignition switch (or any switched 12v source). if you put a switch on anything, it should be the IGN line, not a power line.

if you get a good PSU like the Carnetix P1900 or P2140, they both have integrated automatic startup/shutdown controllers that will turn your PC on and off with the ignition key. it has a delayed power off to allow your PC to properly shutdown before it cuts power.

if you want the ability to override your ignition (leave the PC on with the car off, or leave the PC off with the car on) then you can wire a switch on the PSU's IGN wire.

I installed an override switch for my system. I used a DPDT (center-off) mini toggle switch with a different colored status indicator LED for each override state. this is how I wired mine up:

if you don't want LEDs, then you can use a simple SPDT (center-off) switch like this:

good luck