Run both the power and ground from the computer's power supply.
I've searched, but can't quite find the answer...I will be using my Carnetix to power my transflective Lilli. The PC is in the trunk. I know to run the +12v back to the PSU, but what should I do with the ground? Should I run it back there also? Find a ground spot somewhere closer to the display? Other?
Thanks for your help,
The shorter your ground wire, the better.
If you can, locate a good chassis ground near your monitor. The ground does not have to go back to your psu.
I think he is talking about the negative instead of the ground.... anyway I will connect the negative to the same circuit that is providing the "live" line.
Sure the battery "negative" is also ground it to the car chasis but there are other compunents as well.
Negative and Ground = same thing. Since the OP is using a dc-dc power supply, the ground plane is the same as the vehicle's. It is always best to use the shortest ground wire possible with dc electronics.
Battery "negative" is your ground. Regardless if that point is a wire, or direct metal chassis contact. Ground is ground. All goes back to the battery.
Thanks motorcity...that was my hunch.
The VGA signal comes from the PC, VGA card reference voltage is power supply ground (negative). Monitor reference for VGA signal must be as close to VGA card reference as possible (for a clean signal), the best way you can get this is wiring your monitor ground to your PC ground and NO OTHER GROUND. The shorter and bigger the cable, the cleaner picture (monitor power current flows through the negative and causes a voltage drop in this wire).
Remember always: All car ground points go to the battery, but not all ground points have exactly the same voltage, it depends on how many current is being drawn at each ground point.