Re: direct current loss per foot of wire
- From: me <me@xxxxxx>
- Date: Fri, 2 Dec 2005 22:45:55 +0000 (UTC)
servozoom <servozoom@xxxxxxxxxxxx> wrote:
> I can't seem to find an answer to this question anywhere, So I've
> come to the experts. I need to power a device that requires 500ma of
> 12v dc current, but it has to be 200 feet away from the transformer.
> Will a 1amp power supply provide adequate current over a 14 gauge wire?
> Is there a formula to figure this out? Thanks in advance
Oh boy, where do we even begin:
This question is impossible to answer because you don't provide useful
information. First there's a question of your power source and then
there's a question of your load.
You claim you are 200 feet away from the transformer and then talk about
a 1 amp power supply. So do you mean a 1 amp wallwart? You can't put DC
into a transformer so you'd have to rectify it on the output of the
transformer, it would also be a good idea to regulate it. You also don't
state what voltage is acceptable at the load. 12V +/- what? Bare in mind
that wallwart voltage tends to go all over the place depending on the
load and they are unregulated.
14 gauge wire has a resistance of .00297 ohms per foot (assuming copper
wire, and room temperature, resistance goes up with temperature), so 200
feet of it * 500mA gives you about .3V of drop. That means the voltage at
the output of the transformer must be at least .3V above what you need at
the load.
.
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