help! With I think a ground loop problem please!

[worriedbloke]

I have just spent a not insubstantial amount of money on a couple of day/night cameras, a multiplexor and all the trimmings.
When it gets dark the perfect picture I had degrades to some appalling apparition on the screen!
Having read up on possible causes for this the onlt thing I can find is that it is somesort of ground looop issue when the night time infra reddl ights start firing up.

I am running power and video down the same cable.

Can I just separate the power and voila or am I missing something else?

Any help would be gratefully received!

_________________
Cooler than a fridge full of penguins

[Yoda]

What sort of cable are you using?

When you say you're sending power and video down the same cable it could mean a few different things. More info on the cable would be useful.

Also, how long is the cable?

A ground loop will primarily cause hum bars and/or sync problems which will almost always manifest continuously and not just at night.

Another possibility is that when the IR LEDs activate the increased current drain is playing a role.

What power supplies are you using? You need to be specific on this one in terms of make, model number, rated current and voltage and the regulator technology used as these all play a role.

[worriedbloke]

Panic over! I have managed to solve the issue by running in some rg59 cable to carry just the signal.
It did appear to be a ground loop problem as when I changed the cable I could feel myself acting as ground when I touched the case of the camera!
In hindsight it could only be the extra juice needed by the ir leds that made the problem only manifest at night. As such anyone else who may have the same issue don't use any of these labour saving devices that let you run power and data up the same wire!
This problem occured in only 5m of cable (shop bought rubbish of indistinct type). So as always, if its worth doing, it's worth doing right!

Thank you for your help Yoda it was much appreciated.

_________________
Cooler than a fridge full of penguins

[Pekachu]

there is primarily two ways two stop a ground loop problem
1 use a seperate power sorce at the camera end ( not always fesable)
2 use a ground loop relay this will allow a power brake on the power cableing hense stopping the loop
hope this is of some use

[tesc]

We use the power and video solution a lot.

We have found that some cable sold here as cat5 is actually rubbish.

make sure you're using properly rated cat5 cable, and you shouldn't have any problem.

The apparition or ghosting is usually associated with a poor cable termination - however that should also manifest at night.

[tesc]

There is a distinction between ground loop and ground fault!

Ground Loops are a natural occurrence in CCTV installs and neither the installer nor the customer is to blame --- it's a common phenomena which we need to accomodate.

Ground fault is more serious, and relate to incorrect grounding, of equipment. Could be due to loose earth wire, earth wire shorting against metal. This is the case where you will physically feel shock when touching the case. Ground Faults can be avoided by proper circuit design and wiring.