Noob cabling question

[DKtucson 0]

Hello All,

In looking at some of the results I've gotten with cables it's a mixed bag. At times the inexpensive "combo" cabling that has the signal & power running together works fine---in others I get what can best be described as squiggly lines of "noise" which is remedied by running single cable for video signal to the camera and then supplying power locally closer to the cameras.

In narrowing down the "why" this is happening it seems to be related to using IR cams that consume 500MA of 12vdc.

So--the question for the pros:

1. If I want to run cables back to a centralized location (no local power for the cams close by) would I use Baluns and UTP/Cat5 wire?

2. Is there better "industrial grade" tandem security cam cable that has the RCA/BNC ends and power hookups --(maybe better shielding or less drop over distance?)

3. Are better AC adaptors/Power supplies in need here?

We're looking at inexpensive "hecho en china" IR cams that come with plug in ac power adapters--just for the record

 

Daniel

[rory 0]

typically we use RG59 Siamese Cable.

You then add your own BNC connectors.

Some online stores now sell this in premade lengths as well.

 

Better power supply would be a Distributed Fused Power Supply, something like the brand Altronics or P3. Isolated versions are sometimes required especially when using various different camera brands.

[survtech 0]

You could also try West Penn CC2418 and CC2416. Each has two pairs of CAT 5e siamesed with one pair of either 18 gauge (CC2418) or 16 gauge (CC2416) cable.

 

http://www.westpenn-cdt.com/index.php?option=com_cable_finder&func=BrowseCat&section=ResidentialSpecialized_Cables&cat=4

[DKtucson 0]

Thanks for the prompt replies guys. I found an outfit with both bulk and pre-fab setups.

50ft of bulk with all connectors costs out at just over $10 and prefab at $23--good stuff.

I think I'll pop for a prefab to check signal cleanliness before popping for 1000' of the stuff just to be sure this addresses the issue.

Thanks

Daniel

[Soundy 1]

Hello All,

In looking at some of the results I've gotten with cables it's a mixed bag. At times the inexpensive "combo" cabling that has the signal & power running together works fine---in others I get what can best be described as squiggly lines of "noise" which is remedied by running single cable for video signal to the camera and then supplying power locally closer to the cameras.

In narrowing down the "why" this is happening it seems to be related to using IR cams that consume 500MA of 12vdc.

So--the question for the pros:

1. If I want to run cables back to a centralized location (no local power for the cams close by) would I use Baluns and UTP/Cat5 wire?

2. Is there better "industrial grade" tandem security cam cable that has the RCA/BNC ends and power hookups --(maybe better shielding or less drop over distance?)

3. Are better AC adaptors/Power supplies in need here?

We're looking at inexpensive "hecho en china" IR cams that come with plug in ac power adapters--just for the record

 

Daniel

 

I'll give you 10:1 odds that your problem is a ground loop.

 

The problem with most cheap 12VDC cameras is that the power and video share a common ground. If you get too much difference between the power and ground run for a particular camera, you end up with different-length ground paths, and hence ground-loop issues. With separate power supplies, this will almost never cause a problem, on a central power supply, but the more cameras you add with common power AND video grounds, the worse the problem gets for all of them.

 

Using separate power adapters for each camera is one way to work around it, and they don't have to be close to the camera... they just have to keep the power grounds separate from the other cameras.

 

A better way to work around it is not to use cheap cameras - *good* 12V cameras will have regulators or other designs by which video and power aren't sharing a common ground. 24VAC cameras avoid the issue completely, as they will necessarily have internal rectifiers and regulators.

 

Using baluns in this situation will actually make the problem far worse, because a balun essentially puts a transformer inline with the video signal, thus GREATLY increasing the line length - you end up with a video ground that's technically hundreds of feet longer than the power ground. Baluns are great for killing induced EMI noise, but terrible for ground loops.

[DKtucson 0]

Hello All,

In looking at some of the results I've gotten with cables it's a mixed bag. At times the inexpensive "combo" cabling that has the signal & power running together works fine---in others I get what can best be described as squiggly lines of "noise" which is remedied by running single cable for video signal to the camera and then supplying power locally closer to the cameras.

In narrowing down the "why" this is happening it seems to be related to using IR cams that consume 500MA of 12vdc.

So--the question for the pros:

1. If I want to run cables back to a centralized location (no local power for the cams close by) would I use Baluns and UTP/Cat5 wire?

2. Is there better "industrial grade" tandem security cam cable that has the RCA/BNC ends and power hookups --(maybe better shielding or less drop over distance?)

3. Are better AC adaptors/Power supplies in need here?

We're looking at inexpensive "hecho en china" IR cams that come with plug in ac power adapters--just for the record

 

Daniel

 

I'll give you 10:1 odds that your problem is a ground loop.

 

The problem with most cheap 12VDC cameras is that the power and video share a common ground. If you get too much difference between the power and ground run for a particular camera, you end up with different-length ground paths, and hence ground-loop issues. With separate power supplies, this will almost never cause a problem, on a central power supply, but the more cameras you add with common power AND video grounds, the worse the problem gets for all of them.

 

Using separate power adapters for each camera is one way to work around it, and they don't have to be close to the camera... they just have to keep the power grounds separate from the other cameras.

 

A better way to work around it is not to use cheap cameras - *good* 12V cameras will have regulators or other designs by which video and power aren't sharing a common ground. 24VAC cameras avoid the issue completely, as they will necessarily have internal rectifiers and regulators.

 

Using baluns in this situation will actually make the problem far worse, because a balun essentially puts a transformer inline with the video signal, thus GREATLY increasing the line length - you end up with a video ground that's technically hundreds of feet longer than the power ground. Baluns are great for killing induced EMI noise, but terrible for ground loops.

 

Soundy,

Thank you for the advice...I have also seen the ground loop isolators and was wondering if putting one of those in-line would clean up the picture. Sort of like a ferrite core would clean up radio interference from an appliance or PC component.

I had the pleasure of dissecting some dog-chewed cabling on one of the cheapie cams and the grounds are seperate for power & video from what I saw. I am using seperate power supplies (plug in ac adaptors) for each camera--not a central junction box with wire terminals etc.

[rory 0]

Make sure all cable is run at least 1' away from any high voltage, when using RG59 Coax. If thats the RCA type all in one cable then go even further. More then likely is either the cable or cameras.

 

What are the specs on the cameras?

 

You can also try an isolated power supply based on what Soundy mentioned. Also, most bullet cameras share the ground.

[Soundy 1]

Soundy,

Thank you for the advice...I have also seen the ground loop isolators and was wondering if putting one of those in-line would clean up the picture. Sort of like a ferrite core would clean up radio interference from an appliance or PC component.

 

Ferrite cores and ground loop isolators are two different things. Now granted, the only isolators I'm familiar with are the types used in audio, particularly car audio, but those simply use a 1:1 matching transformer to physically "break" and isolate the audio runs, both signal and ground.

 

I had the pleasure of dissecting some dog-chewed cabling on one of the cheapie cams and the grounds are seperate for power & video from what I saw.

 

Within the wires they are... inside the camera, you'll find them tied together.

[rory 0]

I had the pleasure of dissecting some dog-chewed cabling on one of the cheapie cams and the grounds are seperate for power & video from what I saw. I am using seperate power supplies (plug in ac adaptors) for each camera--not a central junction box with wire terminals etc.

 

normally a short distance from the cable exiting the camera you will see a small plastic block, thats where the single ground from the camera normally splits out to two grounds, one to the video and one to the power. If you were to splice the cable before that block then you will typically just find a single ground, a single video, and a single positive.

[DKtucson 0]

Soundy & Rory,

Thank you for the replies and the wealth of info--so the seperate grounds are a breakout and really just smoke & mirrors , eh?

The specs on the cameras are as follows:

1/4" sharp CCD

512x492 NTSC

480TV lines

0 Lux min Illum

75ohm/1.0Vp-p video output

>48db S/N ratio

>0.48 gamma cirrection

Auto white balance

1/50-1/100,000 sec electronic shutter

auto backlight

dc12v 500mA power adapter

35 IR leds for a range of 20m

 

The ground loop isolators I was looking at are avcailable from

http://www.active-vision.com/Video_Ground_Loop_Isolator_p/aca-bnc-iso.htm