How could I make the ultimate car PC powersupply and what should it do?
I have been reading and thinking a lot lately on how I could approach the power supply problem for my car PC.
There are a few issues to consider:
1- ATX power supply
2- -5v needed for serial ports (IR, GPS and mobile phone functionality)
3- +5v Power good signal for most boards
4- Automatic start-up and shutdown (using the available 12V ACC or ignition line in the car)
I’ve seen several product and combinations of products to achieve one or more of the given goals. For my ultimate setup, I think I will need all 4 features.
The ATX part is not the biggest issue. Several products or homemade products are available of which some of them have a –5v or +5v Power good. Both seem to be rare (Any suggestions anyone ? :D ).
The startup/shutdown seems to be more difficult. With my current knowledge I would go for a solutions that uses the ACPI S4 functionality, also called ‘hibernation’. Problem is that only a few boards support the S4 function. Also an issue that not all software or other peripherals (like a good soundcard) support this function. If good S4 supporting hardware can be found, than some kind of facility has to be made to trigger this feature through the ATX power connector and this facility itself has to be controlled by the ACC or ignition switch of the car. It should also incorporate a small delaying mechanism to prevent startup/shutdown being triggered several times when you try to start the car.
So as you can read, I still haven't found a satisfactory solution to achieve the 4 given goals. I am open for any suggestion to help me out here.