On 24 Feb, 09:42, "Roger Mills" wrote:
In an earlier contribution to this discussion,
Mike Hibbert wrote:



Morning!

I'm looking to install CCTV at the front of the house (long story,
involving kids, eggs, and rather bizarrely, comedy penis's drawn in
butter on the car!)

I bought a camera which runs on 12v and comes with a transformer. But
the lead on the transformer is only about 7' long, which for an
outdoor camera makes it pretty hard to position and still plug in.

I have 3 options I guess, site it somewhere else, buy a new
transformer with a longer lead, or extend the existing one.

My question is, if I simply cut the cable and extend it, will there
be a noticeable drop off in voltage to the camera?

Cheers

Mike

I doubt it. How much current does the camera take? If you multiply the
current by the length of cable and by the resistance per metre of the cable
you intend to use, you can calculate the voltage drop. If you use suitable
cable it shouldn't be a problem.
--
Cheers,
Roger
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The transformer should have a current rating on it somewhere. Use
that figure with the length you need to calculate the voltage drop. A
10% drop wouldn't normally cause any problems

For example. 0.5 square mm cable (that is 3amp mains flex) has a
resistance of 38ohms per kilometre. If you have a 50 metre run that
is a loop resistance of 3.8 ohms. At 100mA that would be a drop of
0.38 volts which wouldn't matter. At 1 amp it would be a drop of 3.8
volts which probably would be a problem