May have bitten off more than I can chew

[loufire 0]

Hello everyone! Veteran fire system and security company owner here. I got us into CCTV installs about two years ago and all has gone well. All installs have been small in scale (4-8 cameras in small residential or commercial buildings) Last week we started an install in a large factory / warehouse putting in 19 PTZ domes. I have been using cat5E for video and rs485 and another cat5E with all four pairs for power. Some of these cable runs are around 900 - 1000 feet after turning corners and all. Here is my problem, Some of the cameras I have powered up and have running look like there is alot of interferrence going on. Now being a factory obviously there is alot of high voltage running in the same path that my camera wiring is. I tried to avoid it but it is literally everywhere. The baluns I am using are semi-cheap like the ones you buy from ebay or wholesale cctv sites. Have i messed up using cat5E? Should I have used rg59 combo cable instead? I am at the point now where running new wire would be a royal pain but if it needs to be done so be it. Please give me some advise and let me know if you need any more information like what equipment used or whatever.

 

Thanks!!

Edited December 12, 2011 by Guest

[Soundy 1]

What make/model are these cameras? Are you running 12VDC or 24VAC?

 

It's not uncommon with many 12VDC-only cameras to get ground loops when using baluns, because the cameras tend to share a common video and power ground.

[thewireguys 3]

Plus if your running 12DC over cat5 900+ feet is not a good idea.

 

Can you post a screen shot from one of the cameras you are having issues with?

[Soundy 1]

Screenshot might help, or even a video clip... seeing the type of interference might give us idea as to the cause.

[loufire 0]

I should have been more specific. I am running power locally for each cameras. Got lucky and there are tons of outlets in the ceiling beams of the plant. Using the power supplies included with the cameras at the outlet and cat% to the camera. Max power run is maybe 250ft. These units are 15 volt. Voltage reading at camera is exactly 15 volts at 250ft.

 

Thanks,

[Soundy 1]

If every camera has its own PSU, then a ground loop shouldn't be an issue.

 

Pics or video of the interference would definitely help.

[loufire 0]

Being new to this I am forgetting important information...sorry...

 

The picture distortion only happens when I pan or tilt the camera from the control desk. Sitting still everything is fine.

[loufire 0]

I will post a video of the problem tomorrow from the plant. This is one of our longtime customers and I will not let him down. This install be be top notch when done if it is the last thing I do.

[thewireguys 3]

Sounds like a compression issue. Are you viewing the cameras from a monitor connected directly to the DVR or are you viewing the cameras using a computer over the network? Does this happen when you hook up a test monitor directly to the camera?

[Soundy 1]

The picture distortion only happens when I pan or tilt the camera from the control desk. Sitting still everything is fine.

Hmmm does the interference happen ONLY on the camera that you're controlling, or on certain others at the same time, or all of them? It sounds like interference is being generated by the control signal, but that SHOULDN'T be an issue with baluns/UTP... possible that a ground loop is being created when the control signal is sent, although that seems unlikely.

 

You might try using a different wire pair for video and/or control... uh, you ARE using only one pair for video, yes? (We've seen a couple instances before on this board where someone was using two separate pairs for video, which caused weird issues).

[loufire 0]

This is while viewing cameras from a 37in HDTV hooked up to the DVR via HDMI. I am using on pair for video and one pair for control. Only two cameras are doing this...oddly the ones I have used long runs of cat5 on. The two closest cameras I used rg59 I had left over from another job.

[Soundy 1]

The pairs in Cat5 are all given different twists specifically to avoid inductive interference between them, but it's still possible it's happening over the length you're running, especially if the two pairs you're using are close to the same twist spacing, or a factor thereof... again, try using a different pair for either video or signal (but not necessarily both).

[thewireguys 3]

If you try a battery powered test monitor this will show you if the inference is a ground loop or not. Unplug the cable from the back of the dvr and connect it to the monitor.

[loufire 0]

So you guys don't think that using cat5 is the problem?

[tomcctv 187]

So you guys don't think that using cat5 is the problem?

 

 

 

Hi. it is hard to say. can you take footage and post it on something like youtube to see what your image is like when you start to control.

 

 

19 PTZ are they all being connected to 1 DVR via the 485 ?? are you using a pc based unit

[Soundy 1]

So you guys don't think that using cat5 is the problem?

I doubt it's BECAUSE you used Cat5. In other words, there's nothing with using UTP that would inherently lead to a problem like this. If my suspicion is correct, there may be inductive interference as a side-effect of the specific pairs you used (just out of curiosity, which pairs DID you use?)

 

If it's a ground loop, that's possibly an issue with having used baluns (not necessarily caused by their specific design or cost). However, the fact that it only happens when you're controlling the cameras, and only on the two with the longest runs, would make me think that's not the case.

 

Question: you say it's just the two cameras with the longest runs that are having this issue? Does controlling one put interference in both of them? What happens if you disconnect the video and/or control for one - does the other still exhibit the problem?

[loufire 0]

All being ran to one dvr. I am running all rs485 through two PTz code distributors to the dvr and joystick controller. I will post video as soon as I can. Thanks so much for all the replies. Hopefully I can help someone like you all have done for me.

[loufire 0]

I used orange for video and green for control. The only distortion is on the cameras being moved. The other is fine until moved.

[Soundy 1]

Sounds a lot more like crosstalk - when you send a control signal up the line, its magnetic field is inducing a signal in the video line.

 

http://en.wikipedia.org/wiki/Category_5_cable#Individual_twist_lengths

 

Maybe try using brown for video - it's the largest difference in twist pitch from the green. See if that at least changes the interference, if it doesn't get rid of it. Actually, you could try brown on one camera and blue on the other, and see if that changes both of them... even if there's still noise, if that at least alters how it looks, that will confirm the source of the problem.

[loufire 0]

Still can't figure out why some of the 19 PTz units go berserk when I pan and tilt at the same time. Pan alone, tilt alone, or zoom alone everything looks good. But when I move the joystick to where it pans and tilts at the same time, the picture flashes or blinks on and off. Any ideas?

[SEANHAWG 1]

Amperage problem. The PTZ draws more amperage during times of activity causing the issues. What kind of power supplies are you using: Voltage and amperage please.

[vin2install 0]

Maybe you need to terminate the rs485 since you have 19 ptz's

[loufire 0]

I have all rs485 ran through termial blocks

[tomcctv 187]

this website who is powerful one in here and Ms. Mica Tang will help you shoot all issue

 

 

i dont think that is the best option at all first $40-50 phone call then the language problem

[vin2install 0]

I have all rs485 ran through termial blocks

 

I meant doing the 120 ohm termination