Re: [CAD_CAM_EDM_DRO] Re: Now that the intro is over...

on 2000-10-07 16:00:38 UTC

---------- Original Message ----------------------------------
From: "Mariss Freimanis" <geckohall@...>
Reply-To: CAD_CAM_EDM_DRO@egroups.com
Date: Sat, 07 Oct 2000 21:21:20 -0000

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>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!) 
>. 
> 
></tt>
>
>
> 
><tt>
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>

Marconi would be PROUD! Thanks for the response.

Discussion Thread

Tom Caudle 2000-10-07 11:07:15 UTC Now that the intro is over... Tim Goldstein 2000-10-07 11:55:32 UTC RE: [CAD_CAM_EDM_DRO] Now that the intro is over... Tom Caudle 2000-10-07 12:57:45 UTC Re: Now that the intro is over... Mariss Freimanis 2000-10-07 14:21:29 UTC Re: Now that the intro is over... Tom Caudle 2000-10-07 16:00:38 UTC Re: [CAD_CAM_EDM_DRO] Re: Now that the intro is over...