Can powersupply mounted too close to DVR cause interference?

[crosseyed66 0]

Has anyone run into interference from having the power supply mounted too close to the DVR? I had a new installer out on a job site and was busy talking to the customer and he had mounted the power supply closer to the units than I normally would have. While he is a rookis installer to CCTV he has been installing access controll systems for over 10 years so he is not just some smuck of the street, and while I did not like it he had already installed the wires in the unit so I let it go. When I went tp power up the system I had all sorts of interference in many of the channels, worse than ever before. I am wondering if that could be part of teh problem. I am not using high end baulns (have used these same ones for over a hundred installs with only a couple problems that were easily cleared up with ground loop isolaters). The system is a 12 volt system, would have prefered a 24 but am using some other equipment that made it more practical to go 12 volt.

Going to reocate the power supply's tonight and give that a shot. Ant other Ideas would be appriciated - they will be forwarded to my blackberry while onsite. Thanks in advance!

[bpzle 0]

how many cameras? how far away is the power supply from the DVR? could be irrelevant and be ground loop... good luck!

[crosseyed66 0]

Power supply was within 6' of. DVR w 25 cameras

[normicgander 0]

Wow, you are quick to call him a rookie installer but you don't seem to have the capability to troubleshoot the install . This is a big problem in our industry in general, and is what differentiates the vital elements of education, trainning and experience.

 

Without knowing the equipment OEM(s), the environmental conditions and layout, it could be external RFI leaking into poorly terminated coaxial cable(s). As mentioned, ground loops encountered with unbalanced coaxial cable systems can be an issue in non-isolated systems. Although unlikely these days, the power supply could be a poorly filtered switch-mode type that is inducing RFI into the cabling. Typically, low-voltage power supplies can be mounted close to the rest of the head-end with no issues discribed. Often power supplies, DVRs and associated network devices are co-located together, preferably in rack cabinets.

[bpzle 0]

Wow, you are quick to call him a rookie installer but you don't seem to have the capability to troubleshoot the install . This is a big problem in our industry in general, and is what differentiates the vital elements of education, trainning and experience.

 

OH NO YOU DI-EN! lol!

 

With that many cameras, my bet is ground loop. Especially on 12vDC cameras...

[trevthespark 0]

hi,

i have mounted psu's close to dvr in the past even on top of one and not had any problems but if you 230v supply is close to your signal cables you will get noise on your picture especially if runs parralel with them.

 

trev..

[rory 0]

depends how close, if it is too close to the video cables then perhaps, but unlikely, just keep the power cable away from the video. Also make sure the cables dont run over high voltage, keep them at least 1' away from lights, etc. Check how the cameras are mounted also, and are they all the same cameras? If mounted onto metal take off and see if it goes away. Power them separately one at a time, incase there is an isolation issue with any of them, some cameras dont have built in Power isolation - you can use separate AC adapters or buy an Altronix Isolated Power Supply. Simplest thing is disconnect all video and then connect one at a time to see if there is still interference. Also check the video on something other then the DVR, incase that is the problem. Baluns and Cat5 cable dont make the troubleshooting any easier. If you are running the power with the video in the cat5, try it using 18AWG or power them locally to the cameras. Check the distance of the runs also. Anything close to the DVR other then the PSU that could be causing an issue, any electrical tools being used nearby?

[Soundy 1]

Argh, I posted a reply to this last night and it seems to have vanished.

 

Your problem sounds like a ground loop, which is very common with baluns when using *cheap* 12VDC cameras (this should be in the site FAQ, seriously). Cheap cameras share a common ground between the power and video, which can lead to two ground paths back to the power supply and DVR, and when you effectively introduce several thousand extra feet to the video run (as happens when you put two baluns inline), you get mismatches and ground loops.

 

If you disconnect all but one camera, I bet the problem goes away... and will start to come back worse with every additional camera you connect.

 

If this is the case, there are a few ways around the problem: one, you can use individual 12V wall-wart adapters for each camera; two, you can use ground-loop isolators; three, you can use cameras that have internal voltage regulators, which effectively breaks the "common" ground between the power and video - this includes dual-voltage cameras, since the issue is not with 12VDC power per se, but with the common ground used in low-end cameras.

 

And no, none of this has anything to do with the proximity of the power supply to the DVR, or with using Cat5, or with baluns *in general*... it's strictly the "interaction" of baluns on low-end cameras.

[Tailbone215 0]

It shouldn't be a problem if the PS is of somewhat decent quality and it in a metal enclosure that provides adequate shielding. I've been cleaning up a site yesterday where the moron installer decided to put four cams per single Altronix SMP3 board supplies. He basically screwed the PS to the wall and, of course, none of these runs are fused. Use decent equipment and mount it properly and you won't have any problems. Unless you see glaring installation problems and aren't getting interference I wouldn't worry.

[scorpion 0]

I agree with everyone that there are too many variable to give you over the internet answers.

 

I would have no problem laying my power supply directly on the DVR without any interference.

 

I find more problems with the actual wall sockets then with any other issue once ground loop issues are determined not to be the cause.

 

You know the bars, and businesses that put up their own walls, and their "brother in law" or who have you does the work to help keep costs down. Check that the socket is wired correctly.

 

Make sure that you are not on the same circuit as a compressor such as for an A/C unit, beer cooler, or standing reachin coolers, or freezers, and such.

 

What is the total usage of all of the cameras? Yeah? What about at night when all of the IR illuminators kick in?

 

What is the size of the power supply. I recently mounted 6 cameras with a 25 amp power supply! Wow! I know, I know it is huge. This is a 16 channel DVR, and the power supply is 16 channels, and I know we are soon to be going up to 16 cameras. This was installed prematurly, but to allow for growth.

 

Most of the power supply may be in the 2amps, or 4 amps, or 8 amps. What size is yours?

 

I have a question! How far are those camera runs? You might be pushing an environment where you may have to go with active baluns even with proper distances.

 

I would remove a few cameras from the power supply, and then turn it back on, and see what the video looks like.

 

If it clears up then you narrowed down the offending camera, or your power supply is too small.

 

You can put those cameras back on circuit, and remove others to use this as a troubleshooting tool. You may have a camera that is in distress bring down the whole system!

 

I would try to plug the power supply in with an extension cord, and go to another room to get a different power socket to see what happens. Take 5 minutes of your time to find out that it is in fact ground loop issues.

 

GROUND LOOP ISSUES! HOW DO YOU FIX THAT CRAP?

You cannot! It will always be there. What you can do is to isolate!

 

On metal buildings, or warehouses such as seen in commmercial districts you can buy a sheet of plastic from hobby shops, or model shops, and cut the plastic in to the shape of the camera mount. This will separate the camera from the metal.

 

For testing purposes unmount the camera, and let it hang by the cord, or use cardboard to isolate the camera. If the video clears up then you are good to go. You found the ground loop, and it ony needs insulation. HEY! DO NOT USE METAL SCREW! THEY WILL BYPASS THE INSULATION ON THE MOUNT!

 

Do not forget that one camera can put interference on other camera channels through the video coax, or through the power supply. Power only one camera. If you have interference then go to that camera, and isolate it. If that does not clear it up then you have other issues.

 

_____________________________________________________

If you are running long runs then switch to 24 volt ac, and use dual voltage cameras. What will happen as you get farther away is that the voltage will drop. The camera cannot pull 24 volt ac, and it will see lower ac voltages. The camera has a built in AC to DC converter (bridge rectifier) It will see 18 volts AC, and it will convert this to DC, and it will act like a 12 volt camera! You cannot run some cameras below 14 volts AC to 13.5 volts AC.

This is a trick that is used for those mini warehouses where the equipment is in the office, and you run wire all the way around the complex.

 

Swap out a balun with a different brand to see what happens. You might have got a momentary bad run of product even though the product is highly regarded in the industry. Poop happens!

 

What do you think?

[Soundy 1]

GROUND LOOP ISSUES! HOW DO YOU FIX THAT CRAP?

You cannot! It will always be there. What you can do is to isolate!

 

It depends on the source of the ground loop. If it's related to an earth ground, then yes, you have to physically isolate the camera. If it's because of a common power/video ground, you can fix it by getting rid of the cheap cameras.

 

If you are running long runs then switch to 24 volt ac, and use dual voltage cameras. What will happen as you get farther away is that the voltage will drop. The camera cannot pull 24 volt ac, and it will see lower ac voltages. The camera has a built in AC to DC converter (bridge rectifier) It will see 18 volts AC, and it will convert this to DC, and it will act like a 12 volt camera! You cannot run some cameras below 14 volts AC to 13.5 volts AC.

 

Uhhh.... wat???

 

Almost *any* dual-voltage camera will run on 12VDC or less internally... the rectifier and regulator are ALWAYS in play. This is why dual-voltage units don't have polarity markings - you can hook up DC power either way, and the rectifier will produce the required output. Input power is simply fed into the rectifier, then into the regulator, and the power board spits out the voltage that the camera internals need.

 

Either way, this shouldn't introduce ground-loop problems, because the power and video grounds are electrically isolated from each other.

[rory 0]

threads merged.