Video Flashing - light to dark to light...

[kao 0]

I've encountered this problem at a few installations and am looking for some advice.

 

Here is a typical setup:

GV-650 card in a Pentium 4 3.0Ghz system.

Cable runs are RG-59 Siamese cable with crimp on bnc connectors.

Power to the cameras is supplied by an Altronix (or similar) distribution box - 24v AC.

All cameras are dual power (12vDC/24vAC)

 

The problem I am having are with the outdoor cameras.

The video is flashing from dark to light (like if someone were moving the brightness slider back and forth on it).

It does this rather quickly - I'd guess 1 to 2 times per second for it to cycle from light to dark.

The strange thing is - it doesnt do it all the time. Sometimes after just sitting for a bit..or sometimes after a reboot - the cameras seem fine..or the flashing is not very noticable.

 

If I bring the cameras inside and connect them to a short (10ft) cable and run power from the distro box, everything on the cameras seems fine when run on a shorter cable.

 

I am at a loss as to why this happens.

I thought these might be reasons causing the problem:

Too long a run. - Nope..same problem on runs under 50 feet.

Something interfering with the video signal or power like being draped over a florescent light in the ceiling. Nope - some cables were pulled together with inside cameras so the cables share the same route and the indoor cameras dont exhibit this problem at all.

Not enough power. Nope - I always test voltage at the camera.

Improper grounding - I'm not sure how to test this. It seems that the only ground that the cameras have is the copper braiding on the coax cable, which connects to the geovision card, which connects to the pc, which grounds in the UPS outlet, which grounds in the wall outlet. The power cables from the camera connect to the distro box, which is plugged into the same UPS as the PC.

 

Any ideas on what would cause this?

[rory 0]

What voltage are they powered on (12VDC or 24AC) and what are the camera models and types?

[kensplace 0]

Could be lens hunting, as its only affecting outdoor cams.

 

The iris is closing to let in less light, but then the iris control circuitry is set up wrong and tells it to let more in, so it opens, then it tells it to let less in, so it closes. The iris just alternates between opening and closing, which could show up like described, try adjusting your auto gain controls, iris controls whatever the cams have.

[kao 0]

What voltage are they powered on (12VDC or 24AC) and what are the camera models and types?

 

24v AC

Cameras are KT&C brand. Model kpc-1000ch

480 TV Lines, 0.5 LUX/F1.2, V/DC Drv., C/CS MOUNT, Dual PW AC24/DC12V

 

 

Could be lens hunting, as its only affecting outdoor cams.

 

The iris is closing to let in less light, but then the iris control circuitry is set up wrong and tells it to let more in, so it opens, then it tells it to let less in, so it closes. The iris just alternates between opening and closing, which could show up like described, try adjusting your auto gain controls, iris controls whatever the cams have.

 

Sounds intriguing, however it is happening to 6 out of 8 cameras. Maybe it is an incompatability between camera and lens? It is a KT&C lens that supposedly matches the camera.

Could this 'lens hunting' happen at random?

Would these controls be exclusive to the camera or would the software/geovision card have any affect as well?

[rory 0]

Hmmm, well they are OEM cameras so more than likely you will need to replace them ... maybe order a GE, Ganz, Sanyo, or Bosch and see how that camera works there .. Ganz and Sanyo would be the least expensive in a good brand .. just get a single one to test ..

 

 

Also, have you tried one of the 2 cameras that are working, in the same location?

[kao 0]

I have tried swapping the cameras around...a non-flashing one with a flashing one. The result was that the non-flashing one started flashing and the flashing one stopped flashing.

That is why I was thinking it was a problem in the cable.

 

But I will try replacing the cameras with better brand name ones and see what happens.

 

BTW, is there any way to test the coax cable for some kind of quality? Some way to see if there is anything disturbing the video signal?

 

The best I can do right now is put a 50ohm terminator on one end and run and ohm test from the other. I get results that are well within the tolorance specified by the terminator.

[rory 0]

can you trace the cable to make sure it is all at least 1 foot away from any high voltage .. ?

 

Also are the cameras set to AI or EI? Switch them to the opposite and see what happens. If its doing this in AI and in EI its fine, then the lens iris has an issue, if its the other way around then the Electronic Iris in the camera is the issue.

[kao 0]

I may be able to trace the cable, but it won't be for some time.

Part of the problem is that the client location is a 3 hour drive one way....so 6 hours round trip.

 

The system seems to "calm" itself down over time and the fading becomes much less noticable.

 

I'll be going to the site once more in the near future to set up a camera that wasnt working due to one of the cable pulls having a broken power wire somewhere (electrician was hired to pull the cable, so they have to fix it.)

[freeflyer 0]

Isn't the effect that Kao is experiencing called blooming?

 

I experienced the same problem a while back with a cheap OEM bullet. It happened when I put the camera on a wall facing the sun & only seemed to happen when the sun was beaming directly towards the camera; I put it down to the camera just not being able to deal with the high level of light and the iris going a bit MAD as it was a cheapo I moved it and it was fine.

 

Kao; Regarding the coax testing; Get a video level meter; one that gives a self calibrating video sync & burst readout; and audio as well if your going to use this feature; I use one all the time now, cheaper than spending eons hunting for other problems where you dont have a clue what is causing them

 

regardz; FF

[kao 0]

Isn't the effect that Kao is experiencing called blooming?

 

I experienced the same problem a while back with a cheap OEM bullet. It happened when I put the camera on a wall facing the sun & only seemed to happen when the sun was beaming directly towards the camera; I put it down to the camera just not being able to deal with the high level of light and the iris going a bit MAD as it was a cheapo I moved it and it was fine.

 

Kao; Regarding the coax testing; Get a video level meter; one that gives a self calibrating video sync & burst readout; and audio as well if your going to use this feature; I use one all the time now, cheaper than spending eons hunting for other problems where you dont have a clue what is causing them

 

regardz; FF

 

Thanks.

 

Which brand/model do you use? Any in particular you would recommend to use or avoid?

[CollinR 0]

Pull your BNCs off and make sure none of the briad is touching the center pin.

[jcolley 0]

could by the lens or the cameras auto iris electronic. Ive had the same thing and it turns out to be one or the other. happens on cheep and expencive cameras

 

Cables: If you have access to a o-scope check for the 1.5v video level. this shouldnt cause hunting though?

 

keep us posted on your findings, please....

[rctech1 0]

Hi,

Another possibility is that the DVR port is flaky. WITHOUT powering down the camera or PC, hook up the camera output to a portable composite monitor, or switching it with another port. See if the problem follows. Try this at the DVR end of the cable and then at the other end, directly at the camera output. I have one customer with a GV900 card, that this periodically happens to. It needs a cold boot to fix. Centrlizing the power to the same UPS as the PC, appears to have solved it for them. Ground loops?

Good luck.

[kao 0]

Thanks...Im doing some other installations for this customer soon...so I'll try some of these things and keep you all posted.

[cctv_down_under 0]

I doubt it will be a fault with the camera becuase you already swapped one, but is the light level there right ont eh threshold for the camera, IE is it possible that it is trying to lift the level and going back again..try adjusting the DC level on the camera itself as this would explain why the other camera did this as well.

 

Check your center pin as you have not ruled out cable yet....try pointing the camera away or twoards a brighter lower ligth source...are all cameras that are acting up int he same lighting conditions levels, make sure that FLK is enabled on the camera aswell, but the best advice would be to try another brand of camera, (something good) in the same spot, this will at least eliminate the cable, and if not then try it on s service monitor to eliminate the dvr....when you checked the voltage of the camera did you check it under load or just the end of the cable, sounds a lot like an undervoltage.