> > > Does anyone know how a cigarette lighter "wires" in on a 3A.
> >
> >Assuming you want it powered all the time, I'd probably wire it in to the
> >brown/white side of the ammeter. Be sure to include an in-line
> fuse, sized
> >to match your maximum expected load. I'd also run a ground
> wire, probably
> >to one of the bolts in the dash brace.
Bill Pugh replied (offlist, but I'm repeating it because I think it's of
general interest, hope Bill doesn't mind) :
> Hi Randall, since all the "stuff" you can run from a lighter socket
> is DC, shouldn't there be some way to check polarity on the socket?
> Or...does it matter?
Bill, you're absolutely right and I simply neglected to mention it.
Some devices (cigarette lighters for example) do not care about outlet
polarity; but the vast majority do. Almost anything with electronics in it
will either not work at all, or possibly even be permanently damaged by an
outlet with the wrong polarity!
So it's important to get the polarity right. The "cigarette lighter"
standard is for the center contact to be positive and the shell to be
negative. Certainly the safest thing is for the car to also be negative
ground (so there's no voltage between the outlet shell and the body), but it
is possible to install a lighter outlet in a positive ground car. You need
to find an outlet that is insulated from it's mounting, or build an
insulated mount for it (which could be as easy as mounting it to the
cardboard glove box). If you do this, I would strongly suggest having two
fuses, one in each lead to the outlet. Many modern devices don't have any
grounded outside surfaces, but some do (for example the ring around the
headphone outlet is frequently connected to the negative supply).
Randall
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