Re: [CAD_CAM_EDM_DRO] Re: Electronic Box Shielding ?

Why can't you just use shielded cabling or perhaps twisted pair cabling as
is done for network wiring?

Smoke
-----Original Message-----
From: beer@... <beer@...>
To: CAD_CAM_EDM_DRO@egroups.com <CAD_CAM_EDM_DRO@egroups.com>
Date: Tuesday, November 28, 2000 10:41 AM
Subject: [CAD_CAM_EDM_DRO] Re: Electronic Box Shielding ?

>On 27 Nov, CAD_CAM_EDM_DRO@egroups.com wrote:
>
>> SO, if I build a box for my electronics and ground this
>> box will it supress electromagnetic energy escaping the box?
>> I'm sure it can so now for the real questions, does the box
>> need to be steel, i.e. magnetic, or will aluminum work as
>> well??
>
>The single biggest source of RADIATED EMF, by far, is all the
>transmitting antennas you have coming out of the box.
>
> Antennas ?
>
>Yes, the wires running from the box to the steppers are a form of
>longwire antennas, and longwires are most efficient. If you are in
>fact concerned about radiation, you certainly want to shield those
>connections inside some conduit.
>
>Now, I have my doubts about how much noise will actually be radiated
>by your stepper system, but as these leads need some protection anyway
>against hot chips and whatnot, encasing them in flexible conduit is
>just good common sense.
>
>A much more troublesome area is noise travelling along the power line.
>This is best handled by a GOOD quality line filter .. may be two of
>them .. and proper grounding techniques inside the box.
>
>Again, a stepper based system is unlikely to create enough energy to
>cause some other device problem, but put one in anyway.
>
>The reverse is not true. Other devices putting energy on the line CAN
>cause problems for the stepper electronics and/or the CPU. One such
>source that I'm intimately familiar with is VFD controllers. There,
>the energy IS large, both radiated and induced.
>
>As far as materials go, any metal box will trap a lot of the RF energy.
>Trapping it all is impossible and even trapping most sends strong men to
>tears. Just ask anyone who's had to deal with FCC Certification issues.
>
>> Then if I connect the ground from this box to a step up
>> transformer and plug it into the wall, can I make my electric
>> meter go backwards? Only kidding in this paragraph. :-)
>
>Don't laugh - capacitive flourescent ballasts are illegal because
>they'll do exactly that. Some phase relationship thing with the
>inductance of the meters.
>
>Alan
>
>--
>
>Alan Rothenbush | The Spartans do not ask the number of the
>Academic Computing Services | enemy, only where they are.
>Simon Fraser University |
>Burnaby, B.C., Canada | Agix of Sparta
>
>
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