power hookup confusion/question
I am a little confused about the power options for a car-computer setup. I am installing my first car-computer and was wondering if anyone could explain how the power is hooked up. I have been reading about DC-DC and DC-AC converters and also the power controller cards. What the optimum setup? Is it to buy a DC-AC converter and just plug the computer and screen into this converter? Or hard-wire them in? Im not sure exactly the best thing to do. The case i have has a 135W power supply. And I am going to get the DSCUSTOMS 7" touch screen (DS700YYV). What would be the best setup? Thanks for everyones help i really appreciate it!
In my opinion (which I hope is shared), the optimum hookup is a DC-DC power source. A computer motherboard (and peripherals) and most electronics all run off of DC power.
Since household power is AC, you wind up with tons of power converters which come with all the electronic equipment that you own.
A car only uses DC power, so you run into a bit of a quandry - most electronics expects you to have an AC power source, which they convert to DC for use. In the carputer case, the "easiest" solution is to probably by a DC-AC converter, then just plug things in normally. Unfortunately, you run into several issues, among which are "wasted" power (since converting is not 100% efficient) and even under-rated wiring in your car; most cars weren't wired with heavy gage wire to support the power requirements of a desktop computer through their cig-lighters (or electrical outlets).
So the best bet is to go with a DC-DC power source; the key is that the power coming out of the power source must be a fairly constant 12 volts. In the case of your car, the voltage varies all over the place from 8 to 20 volts. So you require a DC-DC unit that ensure that you suppress any extra power, but all provide some limited additional power when the voltage drops (obviously you can only do this for short periods).
Opus provides such a solution (as do others - though I'm only familiar with the OPUS DC-DC 150 watt PSU); they also provide an "on/off" switch for computer which can be tied to your "accessories" in your car - when you turn your accessories on (or start your car) the computer receives the signal to boot up - likewise when you turn off your car (the computer receives the signal to shut down / suspend / hibernate /etc,etc).
BTW, I can power a standard computer + my 7" DSCustoms touch screen off of the OPUS with power to spare. I also have a USB GPS system, USB Dlink Radio and USB Network connection running.
If you have any more questions, feel free to ask. I'm far from an expert, and my explanation might not be 100% technically accurate, but it should provide you with the basic ideas.