Interference or bad camera?

[Ronald 0]

Hello all,

 

Last week I installed a PTZ camera on a pole with big commercial flood light at the tip. Not sure if there are other electrical wires for other things.

 

Anyhow, the video images do display, but with ghosting waves scrolling from buttom to top (if I remember correctly) and some flickering (video turning off for a second) from time to time.

 

Any ideas? How can I test for interference?

 

I took a regular box camera and connected it instead using the same cables going to the PTZ, but placed the camera 5 ft lower and sitting on a roof. That camera did not produce any ghosting stripes in the images.

 

Regards,

 

Ronald

[Soundy 1]

Just offhand, I'd suspect a ground loop. Is this a metal or wooden pole? Is the body of the PTZ attached to something grounded? What happens if you unmount the PTZ from the pole?

 

Electrical interference is possible, but you can eliminate this easily if the interference changes when the light is off vs. on.

[Ronald 0]

>Just offhand, I'd suspect a ground loop.<

 

No idea what a ground loop is.

 

> Is this a metal or wooden pole? <

 

Metal

 

>Is the body of the PTZ attached to something grounded? <

 

To the metal pole, but the bracket is painted though. I could try to ground it to the pole if needs be.

 

>What happens if you unmount the PTZ from the pole?<

 

That would be my next step. It's a lot of work to unmount it to the pole.

 

>Electrical interference is possible, but you can eliminate this easily if the interference changes when the light is off vs. on.<

 

The light was OFF when I tested the PTZ.

 

Ronald

[Soundy 1]

A ground lop occurs when you have two separate ground paths at different potentials or of different lengths. For example, the video signal's main ground path the the DVR is via the shield of the coax wire. But if the camera body is grounded to the metal pole, that metal pole is then grounded to earth (and probably via the electrical ground wire as well), which then gives another path to the DVR via its power ground. Having the two separate paths can cause interference, or create another point for noise to enter, or can reduce the system's ability to reject noise that's induced.

 

Physically isolating the PTZ from the pole would be the best way to eliminate this.

 

Some more reading on the subject:

http://www.siber-sonic.com/electronics/GLoopwhatis.html

http://www.fmsystems-inc.com/manuals/GNDLOOPart.pdf

[Ronald 0]

Are you saying I could simply put something (a plastic sheet, for example) between the mounting bracket and the PTZ camera?

 

Also, is there a way that the power supply be causing this as well? The output voltage is 12.35 volts w/out the load. I'd have to test it with the load. Who knows perhaps it drops way too low under load which would explain the fact that the other [box] camera did not inhibit the bad video signal. But then again, that box camera was not mounted on the pole.

 

Regards,

 

Ron

[tomcctv 187]

Are you saying I could simply put something (a plastic sheet, for example) between the mounting bracket and the PTZ camera?

 

Also, is there a way that the power supply be causing this as well? The output voltage is 12.35 volts w/out the load. I'd have to test it with the load. Who knows perhaps it drops way too low under load which would explain the fact that the other [box] camera did not inhibit the bad video signal. But then again, that box camera was not mounted on the pole.

 

Regards,

 

Ron

 

 

this sounds like a power problem. what amp is your power supply and how far is your camera from the dvr. a quick test is ptz your camera and your picture will drop off then come back on. (not enough power to move camera)

[Ronald 0]

The power supply reads 3.35A. The distance between the PTZ and the power supply is roughly 12 meters. The power cable is 16 AWG.

 

The distance between the DVR and the PTZ is about 50m via RG59 coax.

 

I cannot pan and tilt the camera at this point. Reason? Possibly because the PTZ is set to UNTERMINATED via the dip switches. I have yet to power the second PTZ which is TERMINATED. I presume that's the cause, I don't know for sure as I really don't have much experience with PTZ's.

 

Ronald

[rory 0]

Are you saying I could simply put something (a plastic sheet, for example) between the mounting bracket and the PTZ camera?

 

Yeah, a thick piece of plastic. mount that to the pole, then mount the camera to that, make sure no part, not even the camera mount screws, go through and touch the pole. But first take the PTZ off the pole to see if that is the problem. Could also be the high voltage wire is too close to the video/power cable, especially if they are run side by side in the pole.

[Ronald 0]

Ok, thanks! I will check this out on-site. No screws go through the pole, so adding a round piece of plastics around the pole should not be too difficult. Not sure how thick it has to be though.

 

As for the possibility of high voltage power lines interferring, what remedy would there be? Shielding the PTZ cables in metallic flexible pipe?

 

Regards,

 

Ronald

[Soundy 1]

Thickness of the plastic doesn't matter - a plastic grocery bag would suffice. It only has to insulate a few millivolts. But yes, it's important that the mounting screws not make a connection either.

[Ronald 0]

I guess I could use grey duck tape then.

 

Ron

[rory 0]

You want the plastic thick enough so the screw mounting the camera bracket does not go through, 1/2" should be okay, should only be a couple dollars for your local plastic shop to cut you a small piece of that. So, mount the plastic first, then mount the camera bracket to that. At least thats what I did for 2 cameras on a square pole and that eliminated the problem I was having similar to yours - that was AFTER installing an ISOLATED fused Altronix PSU which did not initially completely fix the issue.

[mac security 0]

you could also try disconecting the earth to the post and psu. i take its 24vac. most domes with heater running pull around 3to4 amp?is your psu up to the job? mike

[Ronald 0]

>you could also try disconecting the earth to the post and psu.<

 

The 12VDC PSU is just a in-line adapter, can't remember if the 120v side has a three-prong plug or not, I presume it does. As for the post or pole, you mean for me to find something that is grounded to it and remove it?

 

> i take its 24vac. most domes with heater running pull around 3to4 amp?is your psu up to the job?<

 

The PSU is a 12vdc rated at 3.3a. It came along with the PTZ. If there is a heater, I don't know where it is. Nonetheless, the PTZ housing is rated for -35 celcius.

 

Regards,

 

Ron

[Soundy 1]

^If it's a transformer-type PSU, the line and output grounds will - or SHOULD - be physically separated anyway.

[Ronald 0]

>^If it's a transformer-type PSU, the line and output grounds will - or SHOULD - be physically separated anyway. <

 

Ok, I did test the small in-line power supplies. They provide more than adequate voltage (12.39v) under load. Those are not grounded to anything.

 

Anyhow, I ended replacing those with one big 9-port 5A power supply distribution box (w/ fuses). The interference is gone!

 

Can anyone explain how the in-line power supplies could do such a thing, especially since when I plug them to the cameras nearby (less than 2m distance) everything works fine, but when I extend the output cable to 15~25m distance then I get ghosting horizontal lines in images?

 

Regards,

 

Ronald

[Ronald 0]

I still have a problem with the RS-485 connections though.

 

I used (it was already there) Cat5 UTP cables to run from the PTZ control keyboard to the camera, in series. The last PTZ cam is terminated via dip switches. Can't pan or tilt! I dismounted the last PTZ cama and tested it near the control keyboard, it works fine that way.

 

Any ideas? If I were to double or triple the number of wires utilized within the Cat5 cable, would that help? I know there are high voltage (240v) power lines running nearby in a metallic pipe of its own, for a short distance of about 3m.

 

Regards,

 

Ronald

[Ronald 0]

Never mind. I was able to pull it through. Everything is working now.

 

Regards,

 

Ron