First, this project is fantastic, I found it today and bought one on the spot (from sparkfun). Kudos to all involved.
To business. I have an old dell (700 mhz, running Gentoo with acpi and suspend2 support) that is going in my car to play music. The idea is to have a jukebox in the car, that I can update over wireless from my main computer, so I always have all my music with me. The Arduino is hopefully going to handle power on/off events and control a little serial LCD if I have enough pins left over that displays the currently playing song. I know that I am in WAY over my head, my degree is in IT and I've never done an electronics project of this scale before, so I'm hoping for a little sanity check from you all to let me know if this is even possible.
The LCD part I don't think I'm going to have a problem with, it is well documented all over the place, but the power problem, not so much. I have a 12V DC/DC power supply I bought from mini-box.com (pico PSU) rated at 120W but I very much doubt the computer is drawing near that, the AC PSU that came with the dell is only a 90W, and I've ripped almost everything out of the box except the motherboard and the hard drive (I did add a wireless PCI card though).
The goal is to have the Arduino sense power on the accessories line of the car (+12V whenever the key is in) and activate the power supply. A few seconds later, send a pulse to the power switch of the computer, turning it on. When the car is turned off (ACC line drops to 0), do the opposite, send a pulse to the power switch telling the computer to hibernate, and then a few seconds later, disable power to the power supply.
Questions: Not being an electronics guy, how do I step down the 12V from the accessories line on the car to the 5V (I'm assuming) that the Arduino can handle so it knows when the car is on. Or can the Arduino handle 12V on an input somewhere, so this is a non-issue?
Which is more appropriate for use to control the PSU? a relay/transistor/scr or something else entirely I've never heard of? And as a corollary, if anyone has done something like this before, what did you use? while my googleing skills are pretty good, I don't really know what I'm looking for, much less where to start looking for it (digikey/mouser/jameco/somewhere else)
And last but not least, is this even possible, and with my limited experience doing something like this, is it even within the realm of something I'll be able to handle on my own?
Thanks all, Elliott