EMI shielding material?

[DaveMorris]

A couple notes here:

Twisted pair wire has a minimal effect on outside interference.

Shielding in a cable does absolutely no good at all unless that shield wire is grounded properly. I doubt that the AC unit is wired for that or their own RJ11 cable would be shielded as well.

Rubber jacket has nothing to do with it either. The noise is probably coming from the ballast itself, not the wire. Can you swap wire on the ballasts? If you can, then you could see if the noise is associated with the cable or if it follows which ballast you are plugged into.

 

[shelburn61]

<a href=showthread.php?s=&postid=13771685#post13771685 target=_blank>Originally posted</a> by kcress
Just change your remaining snarl wired IC wire for the same jacketed cord the other one has. Probably cure your problem.

I think this will be my next move.

Dave,
I'm getting pretty conflicting advice here? Keep in mind we a talking small scale here..

The noise is certainly coming from the ballast, but it traveling through the ballast wire. Is it impossible that the rubber jacket could dampen the EMI enough to remedy my problem?

I've moved the ballasts 6+ feet away from the controller and any associated wiring. However, the outgoing wires from the ballasts have to pass within a few inches of the AC phone cable at one point.
Twisted pair wire won't resist EMI enough to help?

 

[kcress]

What you need to realize is that the threshold between your comm having a problem, and not having a problem, is tiny.

No the rubber has no shielding ability at all, BUT, the tiny added distance guaranteed by its jacket thickness may be all that is required to drop below the problem threshold. But wait! There's more! It also reduces the radiation ability of the ballast noise because the wires in the cable will be twisted and not making large radiative loops.

So as I say - try it.

 

[jdieck]

Are the two ballasts the same model? I found some Icecap may cause interference while other models will not.
Sorry to add one more variable but I would suspect electrical noise rather than magnetic.
Will you get the same issue running the AC on a battery?
If you do not there are lectrical filters you can conect the ballast into.

 

[shelburn61]

<a href=showthread.php?s=&postid=13775279#post13775279 target=_blank>Originally posted</a> by jdieck
Are the two ballasts the same model? I found some Icecap may cause interference while other models will not.
Sorry to add one more variable but I would suspect electrical noise rather than magnetic.
Will you get the same issue running the AC on a battery?
If you do not there are lectrical filters you can conect the ballast into.

Same model, at least both were manufactured within the last year. The only apparent difference is the outgoing wires on one have the rubber jacket. Not sure of the difference between EMI and electrical noise. Would the rubber jacket kill electrical noise?

Kcress,
It's not a distance issue. According to the AC monitor I'm getting the same level of interfernce with the wires 3" away or nearly touching. You might have a point with the twisted ballast wires though...

 

[jdieck]

<a href=showthread.php?s=&postid=13776408#post13776408 target=_blank>Originally posted</a> by shelburn61
Not sure of the difference between EMI and electrical noise. Would the rubber jacket kill electrical noise?

Electrical noise travels trough the wires from one plug to the other via your home wires, EMI travels trough the air.
Electronic ballasts internal circuitry transforms the 120 volts in the input to the voltage regulated for the bulb requirements but diferently from magnetic ballasts they also change the frequency of operation from 60 Hz to a range from 200 to 1000 Hz depending on the design. This higher frequency helps maintain a more stable arc and avoid flickering but can create high frequency noise on your power lines that are transferred to all other devices in your home. While most devices are not afected a controller works with very small voltage signals which sometimes are as low as the noise signals thus the interference.

 

[shelburn61]

<a href=showthread.php?s=&postid=13776497#post13776497 target=_blank>Originally posted</a> by jdieck
Electrical noise travels trough the wires from one plug to the other via your home wires, EMI travels trough the air.
Electronic ballasts internal circuitry transforms the 120 volts in the input to the voltage regulated for the bulb requirements but diferently from magnetic ballasts they also change the frequency of operation from 60 Hz to a range from 200 to 1000 Hz depending on the design. This higher frequency helps maintain a more stable arc and avoid flickering but can create high frequency noise on your power lines that are transferred to all other devices in your home. While most devices are not afected a controller works with very small voltage signals which sometimes are as low as the noise signals thus the interference.

Gotcha. The Neptune guy thought it was EMI and there is no difference in interference whether the ballast is plugged into the DC8 or a separate outlet so I guess he must be right?

The wiring passes through a hole in the basement ceiling within a foot of a large steel support beam. Could I use shielding and ground it on the beam?

 

[jdieck]

<a href=showthread.php?s=&postid=13776746#post13776746 target=_blank>Originally posted</a> by shelburn61
Gotcha. The Neptune guy thought it was EMI and there is no difference in interference whether the ballast is plugged into the DC8 or a separate outlet so I guess he must be right?

The wiring passes through a hole in the basement ceiling within a foot of a large steel support beam. Could I use shielding and ground it on the beam?

Once the noise is in your house wiring it does not really matter which outlet it is connected to unless they are conected to diferent phase then the noise has to travel all the way to the outside transforemer and back into the house.
On the shielding, although it can help I am afraid it might not be totally effective.
Usually beams are just supported to the concrete foundation without very good grownding, your best bet for grounding will be to conect it to the ground round pole of one of the outlets.
Do not forget to twist the wires onto each other and ground your reflector(s) if you are using metalic ones.
Also insure that the ballast body is also properly grounded and that the ground plug in the outlet is also really conected to ground on the electrical main box.

 

[kcress]

In all probability the noise is being projected from the random loops of your single stranded ballast wiring. A loop, electrically, being any space between the single strands. That is why a jacketed cable will help minimize it. It's also probably why your 'corded' one isn't a problem, if everything else is the same.

 

[shelburn61]

<a href=showthread.php?s=&postid=13778244#post13778244 target=_blank>Originally posted</a> by kcress
In all probability the noise is being projected from the random loops of your single stranded ballast wiring. A loop, electrically, being any space between the single strands. That is why a jacketed cable will help minimize it. It's also probably why your 'corded' one isn't a problem, if everything else is the same.

I'll let you know what happens

 

[shelburn61]

Last night I switched out the ballast wire for a jacketed cable. I noticed a very slight decline in interference numbers, but still not where I want them. Then I started moving the cords and ballasts around and noticed the interference numbers fluctuated a lot based on their orientation regardless of proximity to the phone cord. It was tough to find a discernable pattern to fluctuation of the numbers based on how I moved the cords so I was blindly using trial and error. Finally the arrangement that seems to work best is to just loop the cords from both ballasts together into a tangled mess. It seems straight runs of ballst cord produce the most interference?

 

[jdieck]

<a href=showthread.php?s=&postid=13782758#post13782758 target=_blank>Originally posted</a> by shelburn61
Finally the arrangement that seems to work best is to just loop the cords from both ballasts together into a tangled mess. It seems straight runs of ballst cord produce the most interference?

Yes, that is what twisting is all about. By twisting the cables around each other EMF is reduced significantly as one twist cancels the other thus reducing EMI interference.