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Hi Everyone,

 

Would be great to get your thoughts on this one.....

 

 

We are currently using CAT-5 (CCA) to supply some analogue cameras with baluns.

The original PSU specified for the project is the Vista 12VDC 4x1A

The longest cable run is 60m but we are having issues on much shorter runs.

Cameras being used are Samsung Bullets w/ IR LEDs that draw 790mA max. current.


During testing today, we were only getting 9V at the camera end / 12.2V leaving the power supply.

At the moment the cabling has been configured:
 - 1 pair for video
 - 1 pair for +ve DC
 - 2 pair for -ve DC

Our Engineer on site doesn't think splitting one of the -ve pairs to use for positive and negative will make any
difference at the camera end. Can anyone explain why?

I'm not a sparky so don't really understand the physics of it, but naturally would have thought more cores would supply more power.


ps. we are changing the PSU's anyway but still want to optimise the power to the cameras.

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CCA

 

Basically its ****, and gives a much higher resistance than standard copper cable. Measure the resistance on the runs, you'll be surprised (maybe)

 

We tend to fire the video down a twisted pair (browns), then power down the two others. So thats the blues twisted together, and the oranges.

Edited by 9651
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Just plugged in the numbers into a voltage drop calculator.

 

The difference in resistance values between CCA and Copper are significant, but it also shows very similiar levels of voltage drop, so you're probably right about using CAT-5 over this distance for power.

 

Putting this down to 1st time rookie specification mistake.

 

We'll try AC tomorrow.

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The Samsung bullets maybe dual powered, most of them are, same trouble I had so switched to ac psu's , so no need for convertor

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or variable psu

Problem here would be current then , increase voltage won't give you increase current or have I mixed that up?

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no, increase the voltage it (dc) will half the current demand, ac theory is more log vs the lin of dc. DC is easier as its pure ohms law, Ac theory adds a little more ie impedance but its similar, ish

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Thanks everyone.

 

Great advice, particularly about the AC.

 

And you are right that the Samsung Bullets come AC/DC so that's good news.

 

 

I'll be sure never to use CCA in future and just stick to good old fashioned copper.

 

 

So can anyone answer my question about the correct use of the pairs for power?

 

This is what is in place currently:

 - 1 pair for +ve DC
 - 2 pair for -ve DC

 

I have since been told that this may be better:

 - 2 pair for +ve DC
 - 1 pair for -ve DC

 

I would have thought that you would split all cables evenly:

 - 1.5 pair for +ve DC
 - 1.5 pair for -ve DC

 

 

Can anyone explain why one option might be better than the others? (I'm getting a lot of "this is how we do it, but don't know why it works" - so wouldn't mind a little more explanation.

 

Thanks :)

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  • 5 years later...

Analog CCTV cameras use coaxial cables, especially the Siamese cable for the wiring. Their videos are recorded via a DVR, which is a Digital Video Recorder where every single camera in a building is connected to the DVR.

Once the system is properly wired and installed, it uses a distinctive mechanism for capturing videos.

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3 hours ago, mecsecurity said:

Analog CCTV cameras use coaxial cables, especially the Siamese cable for the wiring. Their videos are recorded via a DVR, which is a Digital Video Recorder where every single camera in a building is connected to the DVR.

Once the system is properly wired and installed, it uses a distinctive mechanism for capturing videos.

Odd that , many use cat5 for analog aswell 

 

What you on about dude ? Or what's point

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