Ali_2k

Aight lads,
im getting to the next stage of my carpc project but am having trouble understanding how im going to utilise the car's power.

For example (and im going real basic here) my understanding of an electrical circuit is: Positive terminal --> electrical device --> Negative terminal. However, a car is obviously different and im right in thinking rather than it being an enclosed circuit, everything is "grounded" as being the negative terminal?

Heres a wiring diagram of the car (1997 Mini Cooper S):
Ive added in the red+green lines +carpc


As you can see the Negative Terminal is Grounded, so in theory my only option is to bolt a wire to the Positive terminal, run it through to the dash, ground the negative (either to new or existing point), and route the green cable to the ignition? (will be using M2-ATX)

if this is right, can anyone locate the ignition terminals on that diagram?
PDF version available here:
All the best
-2k

lbridges

Can't speak to the red/black/green of your carPC, but #38 (the ignition switch) is the circle (mid-slightly left side of page with the numbers 1, 2, 3 labeled terminals). Hope that plus the wire colors is enough. The info below applies to BMWs around the same era and I understand the Mini uses the same wiring color convention - you probably want to ask or research and not blindly trust this - especially since their wiring diagram doesn't show green as a color - The diagram above is an overview chart - you would need an ignition chart to be sure.
WIRE COLOR POLARITY LOCATION
Battery RED (+) IGNITION SWITCH HARNESS
Ignition GREEN (+) IGNITION SWITCH HARNESS

Did that answer the question?

Ali_2k

yes thanks, i had a quick scout round the switch and there is a green wire, theoretically then i'd just connect the ignition cable from the power supply, thus letting power flow when key is in position 1.

using vladcarpc's image here:


Notice the descriptions on the M2 ATX power supply
RED = +12
White = Ignition
BLACK = Ground

relate this to my diagram, where green is the (white) ignition cable... so bolt that to the green cable coming from my ignition switch and its good to go? right? :P

-2k

lbridges

Well, I would use a voltmeter to make sure the green was indeed the ignition lead before potentially frying a power supply, but to answer you, yes, I believe that is correct. If you don't have a voltmeter perhaps use some strands of wire to jump to a spare light bulb or similar device that would work off 12V.

Ali_2k

heh yes, definatly will be sure to keep it safe, but thanks for your input, im understanding the system much better now.

all the best
-2k