power line to a cctv camera 12v

You already know that you have a 50% chance of being right if you guessed. General rule (but not an answer) is the outer insulation is usually negative (negative is less guarded from exposure, older cars carried negative current in all its metal parts). But before I turn this into a essay, look at where the wires are sodered to and see if there is a + sign for positive and - or ground text or grd abvr. for negative and that would be a foolproof answer.

That's coax, generally the middle wire is signal and the outer shield is ground. You need to use propper connectors to splice coax or your picture will suffer, though with security cameras you can probably cheat and just solder splice the wires and tape the joints and not notice.

If it's two joined together, then it's probably " figure 8 " audio screened cable. In general, the centre conductor will have been designated " + " and the outer shield, ground ( " - " ) but this is only a convention, and not set in stone. If the other cable is the ' video out ', then with 99% certainty, the screen of that one, will be ground. If you then measure with an ohm-meter between the two shields, and they read shorted together, then you can be pretty much certain that the shield of the power cable is " - " and the centre, " + ".

To join to the screw terminals, you can un-plait the screen, and twist it back into a pigtail, slip a bit of sleeving over it, and treat it as a normal wire, or solder and sleeve a pair of thicker wires to the thin ones or, best solution, solder the inner, and pigtailed screen, to solder tags, which can then be firmly screwed to the power unit.

Arfa

thanks for that info but other than a 'wiring simplified' book I got from home depot, I know next to nothing about splicing..could you explain what you meant by proper connectors, the video line is fine it has bnc connection on both ends. I need to connect the power so yareyou saying the inside wire is negative and the outside is positive ?

just so I understand you are describing the power cable right (its two cables joined together, split up on the ends, one has bnc connection on both ends goes from camera to the DVR the other is the power which is what I am trying to connect to the power box. )

When you said un plait i guess youmeant taking off the coating, I was planning to twist the wires (i didnt mention that they are both like vermicelli or very thin strands of hair and not one piece of copper and also the outer wire is about 3 times thicker than the middle insulated one)

and the solder tags I guess would have to be small enough to fit in the power box (not a lot of space and would need 4 tags)?

Your safest bet is to buy an inexpensive voltmeter at Rat Shack or an automotive parts store. Connect the wires to the meter's leads. Connect the center wire to the red lead and the outer shield to the black lead. Measure the voltage with the meter. If the voltage read POSITIVE 12V then the center lead is positive. If it reads negative 12V then the center lead is negative.

Buying a $20 meter is cheaper than damaging your cameras by connecting them backwards. They SHOULD be protected against reverse polarity, but just in case, the meter would be a wise investment.

google google

" cctv camera power connection "

rw

That makes no sense against what the poster was asking ...

Arfa

I think that we must be misunderstanding exactly what your cable looks like. The section with the BNC on each end, must be some kind of concentrically constructed cable - either coax or some other kind of screened cable, but that's neither here nor there.

I, and I think other posters, were assuming that the second ( power ) cable was also some kind of concentric cable, with a central insulated conductor, surrounded by an uninsulated braided shield, surrounded by an outer plastic jacket. That's what it sounded like you were describing. If this were the case, then by " un-plaiting ", I was referring to first exposing the braid, by removing the outer jacket for a short distance, and then ' unpicking ' the exposed braid until its just a bunch of individual strands surrounding the inner insulated conductor, then pulling all those strands together, and off to one side, so that they can be twisted together to form a ' wire '.

Does this sound like what you have as a power cable ? How is this cable terminated at the camera end ?

Arfa

sorry for the later reply, your description is pretty accurate see link below, I can not find any pics showing the inside of the power cable, but it has a barrel i think at that end and the video has a bnc connection at both ends. I have read about using power jacks and adapters which seem to to be easier than soldering whicH I know I will be doing someday but I dont have to time to neither buy the equipment nor learn how to solder. Anyway, I also heard that its not good to use tape ? One cctv says he always splices his connections any tips or thoughts?