Ground loop problem!

[FuTz 0]

Hello,

 

I have installed an mini cctv house system, with 8 cameras + dvr.

 

It's a cheap cameras from ebay (25$), and how i read about them, video and power ground is shared.

 

I'm runing cat5e with baluns, but no more than 120ft of cables, and power is shared from one 12V 5A PSU.

 

When 2 or more cameras, on the individual power supply, there's no picture scrolling bars and other interferences.. what to do?

 

Is the best way to use individual power supply for all cameras (8 cams, 8 supply) or to buy ground isolators... or there's some other solution? Cheap...

 

Thanks for understanding..

 

Best regards from Croatia

[vector18 1]

I'd go with isolators first or try powering your power supply from a different circuit in the house.

[tomcctv 190]

It's a cheap cameras from ebay (25$), and how i read about them, video and power ground is shared.

 

I'm runing cat5e with baluns,

 

 

 

if you have not paid much for your cameras. then you will not have spent enough on baluns.

 

do you have True cctv baluns or are you using these from ebay. i know ebay list them as baluns but there not.

 

also if baluns how many pairs are you using ???

 

 

[FuTz 0]

I'd go with isolators first or try powering your power supply from a different circuit in the house.

 

I was playing arround today with this problem, even powering power supply from a diffent socket, and powering dvr, cameras and monitor from the SAME socket, same problem.

 

When I connect every camera on their supply, it works perfect.

 

 

 

if you have not paid much for your cameras. then you will not have spent enough on baluns.

 

do you have True cctv baluns or are you using these from ebay. i know ebay list them as baluns but there not.

 

also if baluns how many pairs are you using ???

 

 

 

 

I was ordered baluns like that you put a picture of it, and i suspected it was a problem with a balun, i dissambled it and there's nothing in it..

 

- new balun which i'm using it now - A REAL with with coil inside

 

 

On the photo at top (with wire)

 

But almost same problem - interfections decreased a little bit..

 

Solve for the problem is:

 

1. ground loop isolators

2. powering each camera with individual power supply

3. ?? (is there any)

 

Edit: forgot to mention: i'm using 1pair (2 wires for connecting a balun, same color for + and - on both ends)

[Soundy 1]

Ground loop isolators SHOULD help.

Separate power adapters almost certainly WILL help.

 

It's just a matter of which is more cost-effective and/or easier to obtain.

[FuTz 0]

Ground loop isolators SHOULD help.

Separate power adapters almost certainly WILL help.

 

It's just a matter of which is more cost-effective and/or easier to obtain.

 

Price on ebay is almost same for individualy buying 12V 500mA adapters (3.5$), and for ground loop isolators (3.5-5$) / per pc.

 

I think i will take 8 pcs of adapters, because i know it will work 100%.

 

But one question, is this a normal behaviour in cctv installations? How people resolve this case if using power box with 8-16 outputs.. or it's only in camera and their power regulator and normally, video and power ground are separated, not together.

 

Main question is, how to isolate this problem in the future? To use 220V AC cameras or to use ground loop isolators?

 

Thanks everyone!

[Numb-nuts 1]

Just goes to show. don't mess with what you don't understand. Good luck with your problem.

[Soundy 1]

But one question, is this a normal behaviour in cctv installations?

It is quite common when using a combination of baluns, central power supplies, and cameras that have a shared internal power and video ground.

 

Main question is, how to isolate this problem in the future? To use 220V AC cameras or to use ground loop isolators?

The solution is to avoid any one of the above three factors. I tend to just avoid cameras that have this (what I would consider a) design flaw. Dual-voltage (12VDC/24VAC) and 24VAC-only cameras avoid it because the power and video grounds are isolated by necessity of design.

 

Keep in mind that this is just ONE type of ground loop... you can get similar symptoms by having a camera mounted to a grounded metal object (such as a metal building, light pole, etc.) when the camera's case is connected to the video ground.

[FuTz 0]

Thanks everyone for helping me.

 

So, in this situation with shared ground cameras, central power supply, and using baluns, only what I can do is connect every camera to individual supply?

 

Well, if i used coax in my installation, everything will be ok with central power supply?

 

Thank you!

[Soundy 1]

Probably. Remember to pull power wire as well.

[eddy_zjhz 0]

I'm runing cat5e with baluns, but no more than 120ft of cables, and power is shared from one 12V 5A PSU.

 

When 2 or more cameras, on the individual power supply, there's no picture scrolling bars and other interferences.. what to do?

 

 

 

You mentioned"Power is shared from one 12V5A PSU"

Then ,saying"When 2 or more cameras, on the individual power supply, there's no picture scrolling bars and other interferences."

 

What kind of power supply are you using actually?

[FuTz 0]

I'm runing cat5e with baluns, but no more than 120ft of cables, and power is shared from one 12V 5A PSU.

 

When 2 or more cameras, on the individual power supply, there's no picture scrolling bars and other interferences.. what to do?

 

 

 

You mentioned"Power is shared from one 12V5A PSU"

Then ,saying"When 2 or more cameras, on the individual power supply, there's no picture scrolling bars and other interferences."

 

What kind of power supply are you using actually?

 

Here's an explanation:

 

12V, 5A - 2 or more cameras connected - there's a ground loop problem (lines scrolling, (scrolling bars))

 

12V, 1A - one camera, one adapter, everything works great!

 

When i'm using coax and shared power supply - 12V, 5A, everything works great too.. the main problem is in baluns i think.. :-/

[Soundy 1]

The baluns are not the "problem". The "problem" is a particular combination of factors, one of which is a "cheap" camera design. Don't use poorly-designed cameras, you don't have the problem either.

 

As I explained in another thread:

 

A ground loop occurs when you have two or more signal-ground paths that are at different potentials. In a camera, your main signal ground would be via the coax shield, or with baluns, via the wires connected to the BNC shields - if this is the only signal path, all is happy.

 

What happens when you have a camera with common power/video grounds and a common power supply is, you then add more separate signal paths: one normal one via the camera's shield, and another via the camera's power ground, into the power supply's ground rail (NO relation to the power-line earth, it's just a common connection for all the outputs), then back to another camera via ITS power ground, and back to the DVR via that camera's signal ground.

 

Normally the difference between these two paths is very small and thus not a problem... however, if you have the wrong type of coax (foil shield), or a poor shield connection anywhere along the way, or defective coax, or are using baluns (which effectively put a wire coil inline with the signal, thus adding substantial DC resistance), you then have a significant, maybe even measurable difference between the two paths... and you get the classic ground loop. Add more cameras with the same difference, and the problem gets worse.

 

When you use a separate power supply for each camera, you break the multiple paths, as each camera then has its own power ground separate from all the others.

 

The issue tends to be worse with baluns because of how they work, but as you see, it CAN happen with coax as well.

 

The one common denominator: cameras with poor design that have a shared video and power ground. This type of design - shared signal and power grounds - is actually pretty common in consumer-grade electronics, and can be just as troublesome in other fields as well.

[FuTz 0]

I'm sorry I was booring with mean I can resolve it somehow.. and I very very appreciate on your long post and explanation what you gave me.

 

My cctv installation is very good maked, so i will isolate this with putting individual adapter on every camera.

 

Reason why i bought cheap cameras is that that i had a very low budget, and i had to put this camera - but except that ground loop problem - everything is ok.

 

I'll put power bar with 8 sockets and 8 adapters with power supply 12V, 1A per each camera and that will solve my problem.

 

Thank you mate, you've been very helpful person.

[yakky 0]

The baluns are not the "problem". The "problem" is a particular combination of factors, one of which is a "cheap" camera design. Don't use poorly-designed cameras, you don't have the problem either.

 

As I explained in another thread:

 

A ground loop occurs when you have two or more signal-ground paths that are at different potentials. In a camera, your main signal ground would be via the coax shield, or with baluns, via the wires connected to the BNC shields - if this is the only signal path, all is happy.

 

What happens when you have a camera with common power/video grounds and a common power supply is, you then add more separate signal paths: one normal one via the camera's shield, and another via the camera's power ground, into the power supply's ground rail (NO relation to the power-line earth, it's just a common connection for all the outputs), then back to another camera via ITS power ground, and back to the DVR via that camera's signal ground.

 

Normally the difference between these two paths is very small and thus not a problem... however, if you have the wrong type of coax (foil shield), or a poor shield connection anywhere along the way, or defective coax, or are using baluns (which effectively put a wire coil inline with the signal, thus adding substantial DC resistance), you then have a significant, maybe even measurable difference between the two paths... and you get the classic ground loop. Add more cameras with the same difference, and the problem gets worse.

 

When you use a separate power supply for each camera, you break the multiple paths, as each camera then has its own power ground separate from all the others.

 

The issue tends to be worse with baluns because of how they work, but as you see, it CAN happen with coax as well.

 

The one common denominator: cameras with poor design that have a shared video and power ground. This type of design - shared signal and power grounds - is actually pretty common in consumer-grade electronics, and can be just as troublesome in other fields as well.

 

Great post, this should be "stickied"