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Re: [mach1mach2cnc] Re: shielded cable

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  • qconvers@aol.com
    Sorry, I know this has been covered before... but the braiding on a shielded cable... where is the optimum place to connect each end.. or do you connect both
    Message 1 of 5 , Aug 2, 2009
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      Sorry, I know this has been covered before... but the braiding on a
      shielded cable... where is the optimum place to connect each end.. or do you
      connect both ends?

      I've just plugged my machine in and watched it move for the first time..
      whooo hooo! :0)

      Regards Dave




      [Non-text portions of this message have been removed]
    • JCullins
      Makes you feel good all over don t it !! Jim www.soundlogicus.com Plasma THC-300 Serial Spindle Speed control ... From: mach1mach2cnc@yahoogroups.com
      Message 2 of 5 , Aug 2, 2009
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        Makes you feel good all over don't it !!
        Jim

        www.soundlogicus.com
        Plasma THC-300
        Serial Spindle Speed control


        -----Original Message-----
        From: mach1mach2cnc@yahoogroups.com [mailto:mach1mach2cnc@yahoogroups.com]
        On Behalf Of qconvers@...
        Sent: Sunday, August 02, 2009 8:09 AM
        To: mach1mach2cnc@yahoogroups.com
        Subject: Re: [mach1mach2cnc] Re: shielded cable

        Sorry, I know this has been covered before... but the braiding on a
        shielded cable... where is the optimum place to connect each end.. or do
        you
        connect both ends?

        I've just plugged my machine in and watched it move for the first time..
        whooo hooo! :0)

        Regards Dave




        [Non-text portions of this message have been removed]



        ------------------------------------

        www.machsupport.com - Web site AccessYahoo! Groups Links
      • oxforduniv
        The official termination point is one end, the end that the signal originates from. Personally I connect all shields to the one common earth star point end.
        Message 3 of 5 , Aug 2, 2009
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          The 'official' termination point is one end, the end that the signal originates from.
          Personally I connect all shields to the one common earth star point end.
          Al.
          --- In mach1mach2cnc@yahoogroups.com, qconvers@... wrote:
          >
          > Sorry, I know this has been covered before... but the braiding on a
          > shielded cable... where is the optimum place to connect each end.. or do you
          > connect both ends?
          >
          > I've just plugged my machine in and watched it move for the first time..
          > whooo hooo! :0)
          >
          > Regards Dave
          >
          >
          >
          >
          > [Non-text portions of this message have been removed]
          >
        • qconvers@aol.com
          In a message dated 02/08/2009 15:18:54 GMT Daylight Time, oxforduniv@yahoo.com writes: The official termination point is one end, the end that the signal
          Message 4 of 5 , Aug 2, 2009
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            In a message dated 02/08/2009 15:18:54 GMT Daylight Time,
            oxforduniv@... writes:

            The 'official' termination point is one end, the end that the signal
            originates from.
            Personally I connect all shields to the one common earth star point end.
            Al.



            Thanks Al,

            So, connect them all together inside my aluminium control box and earth
            them to the box? or just connect them together?

            At the motor end, just cut them back?


            Regards Dave K

            In a message dated 02/08/2009 14:39:52 GMT Daylight Time,
            james_cullins@... writes:

            Makes you feel good all over don't it !!
            Jim

            www.soundlogicus.com
            Plasma THC-300
            Serial Spindle Speed control

            Oh yes! I'll be smiling ear to ear for the rest of the day :0)





            [Non-text portions of this message have been removed]
          • Dr Mark Vaughan
            It actually depends what the cable is used for. For signal cables, those you use for encoders and step direction signals, the screen should be terminated at
            Message 5 of 5 , Aug 2, 2009
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              It actually depends what the cable is used for.

              For signal cables, those you use for encoders and step direction signals,
              the screen should be terminated at one end only. This is because if we
              terminated both ends then current can flow down the screen which would
              induce a signal upon the wires inside, so by terminating at one end only no
              current can flow. You will actually find some encoder signal cables have two
              internal screens which are insulated the basis being that both ends can be
              terminated and you have a double overlapping independent screen.

              The star earth or 0V point is a good place to attach the screen to, each
              screen individually going to this point. Another method is to use EMC glands
              or horse shoe clips where the cables enter the cabinet, strip back the outer
              cable insulation and terminate the screen at that point, which is sort of
              half way along the cable, but again since it only has one termination then
              no current can flow.



              Now if you playing with the power cables to a motor, those power signals are
              so big you wouldn't be able to effect them much if the screen does carry a
              current, and in many commercial servo motor applications you will see the
              screen used as an earth protective conductor for the motor as well as to
              keep the signals from those hefty power conductors to the motor constrained
              within the cable. You'll find similar situations between VFD and Motor, you
              will find some contradictions with VFD's, some VFD manufacturer only like
              the motor power cable screen terminated at one end, whilst others recommend
              both ends, and many safety technical standard insist on termination at both
              ends, for power cables I always terminate at both ends.



              It's also worth noting that there was a whole technical theory shift during
              the 90's in this area. Communications engineers have always used the modern
              method, but many Universities courses taught electrical/ electronic students
              to terminate all screens on both ends. Then at the beginning of the 90's new
              EMC laws came into the EU with potential hefty legal penalties attached,
              there were some EMC laws before this from the 1971 era but these were
              ignored by many firms. Many products failed before they discovered engineers
              were taught in error, now the teachings are as above, but you will find
              older texts doing it the old way.



              Regs Mark



              Dr. Mark Vaughan Ph'D., B.Eng. M0VAU

              Managing Director

              Vaughan Industries Ltd., reg in UK no 2561068

              Water Care Technology Ltd, reg in UK no 4129351

              Addr Unit3, Sydney House, Blackwater, Truro, Cornwall, TR4 8HH UK.

              Phone/Fax 44 (0) 1872 561288

              RSGB DRM111 (Cornwall)



              From: mach1mach2cnc@yahoogroups.com [mailto:mach1mach2cnc@yahoogroups.com]
              On Behalf Of qconvers@...
              Sent: 02 August 2009 15:37
              To: mach1mach2cnc@yahoogroups.com
              Subject: Re: [mach1mach2cnc] Re: shielded cable







              In a message dated 02/08/2009 15:18:54 GMT Daylight Time,
              oxforduniv@... <mailto:oxforduniv%40yahoo.com> writes:

              The 'official' termination point is one end, the end that the signal
              originates from.
              Personally I connect all shields to the one common earth star point end.
              Al.

              Thanks Al,

              So, connect them all together inside my aluminium control box and earth
              them to the box? or just connect them together?

              At the motor end, just cut them back?


              Regards Dave K

              In a message dated 02/08/2009 14:39:52 GMT Daylight Time,
              james_cullins@... <mailto:james_cullins%40sbcglobal.net> writes:

              Makes you feel good all over don't it !!
              Jim

              www.soundlogicus.com
              Plasma THC-300
              Serial Spindle Speed control

              Oh yes! I'll be smiling ear to ear for the rest of the day :0)

              [Non-text portions of this message have been removed]





              [Non-text portions of this message have been removed]
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