EMI shielding material?

S

shelburn61

New member
I'm having trouble with the electromagnetic interference from my MH ballasts disrupting my Aquacontroller. The ballast wires and AC comm wire all have to be run through a small whole in the floor down to the basement sump. The wires are not physically touching, but I am still getting interference. Can pvc drains conduct EMI?

What is the best material to use as a shield/sheath for the Aquacontroller communication wire?
 
Certainly PVC can do nothing for EMI.

Your comm wire should be cable that is sheilded twisted pairs.

You could also try a snap-on balun around the MH wires near the ballast to reduce the EMI leaving the ballast. Note: An example of a baluns are those lumps you see in cables like the cable into your LCD computer screen, etc. They make snap-on ones.
 
Stug,
I'm just talking about the standard telephone cable connecting the ACjr to the DC8. The Neptune guy said my only options were to physically separate the wires (won't work for me) or shield the phone wire...

So one of those filters on each ballast wire would block/absorb EMIs along the whole length of the wire?
 
Well, you could get some "shield braid" and pull the wire through it.

The stuff comes in rolls and looks like braided flat strap. When you push it together it opens up like chinese "finger-cuffs".

Its not easy to come by but I am looking at a roll of it, How much do you need.

Stu
 
The other thing do is if it uses normal phone cable replace with with a good twisted pair cable. Have a local electronics place use some CAT 5 or CAT 3 cable to make a phone cord out of, you will just have to have them install the RJ 11 connectors.

Kim
 
"you will just have to have them install the RJ 11 connectors."

I bought RJ-11 connectors, the tools & cable all at HD.

I'm not sure if HD carries shielded Cat 5/6 wire.....

Stu
 
<a href=showthread.php?s=&postid=13764497#post13764497 target=_blank>Originally posted</a> by kgross
The other thing do is if it uses normal phone cable replace with with a good twisted pair cable. Have a local electronics place use some CAT 5 or CAT 3 cable to make a phone cord out of, you will just have to have them install the RJ 11 connectors.

Kim
Click to expand...

electronics place meaning radio shack?
 
I did some testing tonight. I'm running 2 identical Icecap 400w ballasts, but only one is causing problems. The wiring from the ballast causing problems is just 3 bare wires in fabric sheathing, but the other has heavy duty rubber-coated cord running from the ballast. Is it as simple as using the rubber-coated wire to kill the interference?

Stu,
I could use 6+ feet of the sheathing or should I just go with the Cat 5 cable?
 
I'd bet a buck just adding shield jacket won't work as the noise in this case is current based, and hence inductive, which cares not in the slightest about shielding.
 
<a href=showthread.php?s=&postid=13766623#post13766623 target=_blank>Originally posted</a> by kcress
I'd bet a buck just adding shield jacket won't work as the noise in this case is current based, and hence inductive, which cares not in the slightest about shielding.
Click to expand...

You'll have to dumb things down for me a bit :) Are you addresing my last post or someone else?
 
Sorry shelburn61! I was referring to stugray's kind offer of shield braid. I doubt all the effort would be worth it.

'Current noise' is predominantly magnetic in nature. It couples into neighboring wires thru transformer action. The other form of noise is coupled in via mutual capacitance. Shielding works well for that.
 
kcress,

I'm running 2 identical Icecap 400w ballasts, but only one is causing problems. The wiring from the ballast causing problems is just 3 bare wires in woven nylon sheathing, but the other has heavy duty rubber-coated cord running from the ballast. Is it as simple as replacing the bare wires with heavy duty cord to kill the interference or is one ballast giving off more EMI?

The ferrite snap-on filters didn't help. Sheilding apparently won't work. Is my only option the Cat 3/5 wire??
 
Last edited:
You just need better phone wire. Get something that is twisted pair like any Cat wire. That is why they twist the wires inside around each other, it reduces crosstalk in the wires which is a form of interference. That may not be enough if the interference is high enough. I suggest a lead shield j/j.
 
<a href=showthread.php?s=&postid=13769820#post13769820 target=_blank>Originally posted</a> by hoosierpat
You just need better phone wire. Get something that is twisted pair like any Cat wire. That is why they twist the wires inside around each other, it reduces crosstalk in the wires which is a form of interference. That may not be enough if the interference is high enough. I suggest a lead shield j/j.
Click to expand...

OK. does it need to be shielded or will regular Cat5 be enough?
 
Last edited:
Hard to say. Finding well shielded wire probably won't be that easy. The wire is cheap though, just go to a big box home improvement store and you will be able to find regular twisted pair.
 
Just change your remaining snarl wired IC wire for the same jacketed cord the other one has. Probably cure your problem.
 
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