Re: [CAD_CAM_EDM_DRO] Electronic Box Shielding ?

In a message dated 27-Nov-00 17:33:14 Central Standard Time, currinh@...
writes:

> With chopper stepper drivers, computer electronics, etc. I'm
> convinced there is a great amount of electomagnetic noise
> created. I'd like to contain and master it. :-| >>

NOT a dumb question! There is a HORRIBLE "EMI hash" from all that! But an
alum. box is sufficient. There is no need to make a cobalt-sheet box for
this box. What there IS need for is to "bypass" and "shield" the CONNECTIONS
to/from the box! The use of opto-isolators for the inputs to these drivers
is an excellent move, if somewhat cumbersome (i.e., you can't drive an
opto-isolator's input from a CMOS gate, at least "ideally") The hash caused
by "chopping" can be badder, yet; use shielded 4-lead cable from each moto to
this box, and make EXCELLENT electrical connections (either "gas-tight"
crimps or SOLDER!), preferable INSIDE, rather than to "screw-terminals" on
the outside.

> 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?? >> Alum. is OK. Steel may be better, but probably not really
> necessary. It's airborne EMI, not magnetic flux, that causes "noise" you
> are trying to shield.
>

Warning: I am uneducated, un-degreed, and quite ignernt. I kain't even
spel. So, beware how you use MY advice! (BTW, I have been there, done that,
and am doing this very thing right now, and GOOD workmanship and CORRECT
connections will preclude 99% of problems. The other 1%? Well-made metal
box, best, "store-bought" driver/power-supply from motor-mfgr., if at all
possible).

Jan Rowland


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