what extra wires would i have to run for a relay? You said there are two extra wires, my guess would be Acc and Ign? My main concern about a relay is where i'd put it.... Also with a relay when i turn my car off it sounds like the pc would turn off, unless i put an addition switch infront of the relay which would bypass the relay and direct signal directly to the pc.
power input (for the relay coil). the relay power input should be wired to the ACC or the IGN circuit. the ACC circuit (first key position) is live when the key is in the 'ACC' or 'run' position. the IGN circuit is live only when the key is in the 'run' position.
a standard bosch-style relay has 4 or 5 leads. 86 is the coil power (from ACC or IGN line), 85 is coil ground, 30 is your PSU's power source (car battery), 87 is the switched output (87 and 30 are connected when the relay coil is powered). on 5-lead relays, 87a is the other side of the 'switch' (87a and 30 are connected when the coil is NOT powered. for your setup you have no need for 87a, so just leave it disconnected).
I think I remember from one of your other posts that you wanted to use a lighted switch. if that is the case, then it would only be 1 extra wire (since you would be wiring a ground wire anyways )
laptop, it can run off it's own battery. when the relay switches off, the laptop will simply stop receiving power from the car's battery. it would continue to operate with it's own battery until you turn it off (or it's battery dies). if you want to continue powering it from the car's battery without the engine running, then you simply leave the key in the 'ACC' position
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I would suggest that you power your LCD Monitor from the 12VDC output of your power supply. The raw 12VDC from the car's system usually runs about 14.8 with spikes and sags on the line from starting and as other loads are switched on and off. The thought is that the regulated output of your PSU will give you generally better prefromance and life on one of the most expensive components in you system.
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Fusion, question about a relay, if i have a relay before my switch when my car turns off is it going to kill all power to my switch? I'm guessing this is when the valet switch would come into play by by passing the acc line (relay) and sending power straight to the switch?
a valet switch should be wired like this:
you could wire an 'override' switch, but I don't really see the point. I can't imagine a scenario where you would need to use the carputer without the ignition key. if you want to use the carputer without the engine running, then just put the key into the 'ACC' position.
IMO, an override switch would defeat the purpose of using a relay in the first place, so I wouldn't recommend it. that being said, if you still want to wire an override switch then you can wire it in like this:
Wow, thanks for the diagrams, it's really nice being able to see what people are actually talking about. Thanks man, the main reason for the switch is because it's about the only way the GF will be okay with me spending 2 - 3 weeks working on this and giving her no attention, because in her opinion the switch "looks cool", worst mistake ever is take a trip to radio shack w/ a girlfriend to buy a switch, they make you buy the "pretty one" so i end up w/ a $5 switch that looks like it belongs in an F-15 rather than a car.
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