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managing electrical noise

I've been researching my control refit for a plasma cutter...

Plasma cutters put out a huge amount of electrical noise, especially when establishing an arc. Plus there is a twenty-five foot run where the plasma power, servo power, I/O, encoders, air lines, etc. share the same trough on my table. Trouble just asking to happen. And from what I've read, many folks have had a lot of issues.

OK, shielded cable all around grounded on one end. Anything else special for the cables? I'd like to get the wire ordered.

I've seen a ton of suggestions on encoder and I/O noise reduction but I think a lot of folks don't know what they are talking about. trouble is, I don't know who to listen to. In particular attaching small resistors, small capacitors, and ferrite cores. I plan on using differential encoders from USdigital and all I/O will be at 24 volt DC with normally closed inputs as much as possible.

suggestions? In particular is there anything to do with the plasma head to reduce electrical noise at the source? I'm puzzled that I've not seen anything on this.

Karl

Reply to
Karl Townsend
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You can wrap the cables in aluminum foil. Cuts down on a tremendous amount of the radiated and picked up noise.

Reply to
Calif Bill

Karl I suggest you join the Yahoo group Plasmacutting. The moderator Jim Colt is a Hypertherm rep and is a wealth of info. He has posted good information on shielding high frequency start plasma cutters. I used a contact start machine Thermal Dynamics 81 and the electrical noise isn't a problem with these types of cutters. Steve

Reply to
Up North

Thanks for the tip. I'll cruise on over search and lurk a bit.

Karl

Reply to
Karl Townsend

The basics of shielding are

1) to make sure power (the gun) and return (ground clamp) cables run next to each other, as closely as possible. 2) shield that pair of cables within a conductive envelope grounded at one end only 3) shield everything else within a different conductive envelope grounded at one end only

Now of course practically applying this to a plasma cutter or welding application has its own challenges, but that above is the basic idea.

Dave

Reply to
spamTHISbrp

Greetings Karl, The encoders at this link:

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supposed to be more immune to electrical noise. That's what Gecko Drive told me. One of their engineers. Talked my ear off. Anyway, they are cheaper than US Digital encoders and I bought some from, I think, Digikey. I was also informed by the same engineer to solder a .01 mfd capacitor across the two square U shaped loops inside the US Digital encoder case to help combat noise. Which I did, and it worked. ERS

Reply to
etpm

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