Re: Now that the intro is over...

Hi,

Thanks for the invite! It is a giant spark-gap machine which means it
radiates RF prodigiously across the entire spectrum. I had one
project a while ago where the cure for this enviroment was shielding
and filtering, and lots of it.

Here's what it took:

1) Use shielded cable for the motors; 3-conductor for servoes, 5-
conductor for steppers. The extra wire in each connects to the motor
case and the far end goes to a common ground.

2) Place the drives (and the power supply if you can)in a steel box.
Steel works much better than aluminum for magnetic shielding.

3) If encoders are used, use a shielded cable as well.

4) Ditto for the step/direction/common signals.

5) If the power supply is in the box, use a good quality line RFI
filter like a Corcom on the 115VAC input. If not, make an LC low-pass
filter using two 150 uH chokes in series with the +supply and ground
leads where they enter the box and a low-inductance .47 uF film
capacitor across the output ends of the chokes.

6) Ground the cable shields at the box end. Do not ground the far
ends!

7) Check the effectiveness of your work by placing a small battery
operated transistor radio in the box. Have it tuned to a strong local
station. Use a headset to hear it when you seal the box. If done
well, you should hear nothing but a hiss.

Mariss

--- In CAD_CAM_EDM_DRO@egroups.com, "Tom Caudle" <tom@t...> wrote:
> --- In CAD_CAM_EDM_DRO@egroups.com, "Tim Goldstein" <timg@k...>
wrote:
> > There is a lot of EMF interference with a plasma rig and servos
are
> more
> > sensitive to picking this interference up in my limited
experience.
>
> Plasma torch = giant spark gap generator. Needs attention to EMI
> shielding and drive circuit isolation. One of the reasons I am
> looking at the Gecko 320 drive is that it is self contained and
could
> possibly be driven with optoisolated step and direction commands
with
> no common ground. Years in the design of large switching power
> supplies taught me respect for what interferance can do to control
> electronics. (Jump in Mariss if you want!)
.