So after having a crappy relay setup turn on my carpc over the past couple years, I got sick of the little nuisances that my setup had.
I finally found the time to program an arduino and run harnesses throughout my car to properly turn on and power my carPC, which is a netbook. I haven't seen anyone do something like this here and after a quick search, I figured I would post up my setup for other's benefit.
I used an Arduino Pro Mini, a SmartSain 4 channel Relay board, various 12v-5v inverters, and some other misc stuff. The inverters were an efficient, cheap way of stepping 12v down to 5v. Using just a vreg and heatsink was bulky and created a ton of heat.
The setup runs MUCH better than my original setup and does so much more.
The Arduino controls the relay board and based on inputs to A1 (Ignition trigger) and A2 (Interior lighting trigger), the relays are switched. It also controls my angel eyes for Welcome Lighting and DRL operation, as well as the carPC power supply and angel eye driver power supplies.
Relay 1 turns on the carPC when A2 is high. It switches the relay for 2.5 seconds, then shuts off.
Relay 2 turns on the power supply for the carPC. It is switched when A1 is high.
Relay 3 turns on the power supply for the Angel Eyes. It is switched on whenever the Arduino is powered. I did this because I am using the Arduino as a controller for Welcome Lighting. So the arduino will send a PWM signal to my angel eye drivers and tell them what to do. When the program starts, the drivers are off. When it sees a signal on A2, it fades the angel eyes on. When there is no signal, it fades them off. When A1 is present, the angel eyes are turned on for DRL operation.
Relay 4 is currently not used.
If anyone is interested in the code or wiring schematic, I can post/draw something up.