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RE: [taigtools] Re: Home switches, was Adding limit switches

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  • Bertho Boman
    Home, or reference, or 0,0,0 can be just different names with or without a calculated offset. I completely fail to understand why you state that a switch
    Message 1 of 22 , Oct 5, 2008
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      Home, or reference, or 0,0,0 can be just different names with or without a
      calculated offset.



      I completely fail to understand why you state that a switch cannot be
      accurate. Various home sensors are normally used. Here is an example of a
      very accurate switch, much better than the mill itself:

      http://www.vinland.com/Opto-Interrupter.html



      Even a regular micro switch is surprisingly accurate.

      Bertho



      From: Will Schmit Sent: Sunday, October 05, 2008 17:47
      I think it is important to realize that 0,0,0 (origin) and "home" are
      different concepts.


      The wild idea that a switch could reliably tell the machine that it has
      arrived at any specific location is folly.
      The idea that it is telling the software that the tool is "out of the way"
      is more realistic. The best switch will never be repeatable.





      [Non-text portions of this message have been removed]
    • Will Schmit
      Thanks Bertho. I have used them in the past, as encoder counters for focusing tapes in a huge camera I was working on. As you noted, they failed with the least
      Message 2 of 22 , Oct 6, 2008
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        Thanks Bertho.
        I have used them in the past, as encoder counters for focusing tapes in a huge camera I was working on.
        As you noted, they failed with the least dust they go south.
        I stand corrected.



        ----- Original Message ----
        From: Bertho Boman <boman01@...>
        To: taigtools@yahoogroups.com
        Sent: Sunday, October 5, 2008 4:39:43 PM
        Subject: RE: [taigtools] Re: Home switches, was Adding limit switches


        Home, or reference, or 0,0,0 can be just different names with or without a
        calculated offset.

        I completely fail to understand why you state that a switch cannot be
        accurate. Various home sensors are normally used. Here is an example of a
        very accurate switch, much better than the mill itself:

        http://www.vinland com/Opto- Interrupter. html

        Even a regular micro switch is surprisingly accurate.

        Bertho

        From: Will Schmit Sent: Sunday, October 05, 2008 17:47
        I think it is important to realize that 0,0,0 (origin) and "home" are
        different concepts.

        The wild idea that a switch could reliably tell the machine that it has
        arrived at any specific location is folly.
        The idea that it is telling the software that the tool is "out of the way"
        is more realistic. The best switch will never be repeatable.

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



        [Non-text portions of this message have been removed]
      • Keith Bucklitch
        Thanks Guys for the informative comments recently posted. I need to sit down and read through them to determine the best way to proceed from here. Just one
        Message 3 of 22 , Oct 6, 2008
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          Thanks Guys for the informative comments recently posted. I need to
          sit down and read through them to determine the best way to proceed
          from here.

          Just one point I am still unclear about. No one has answered my
          query as to how one starts up the system once it has been brought to
          a halt by the activation of a limit switch. Does one simply issue a
          MDI command to move away from the limit position? Obviously the
          software is still working, but is power still on tap to the
          motors? Perhaps I have got the wrong end of the stick here. I had
          in mind that when a limit switch was activated, it stopped EVERYTHING
          on the machine - spindle, steppers, coolant etc. Does it simply stop
          the stepper motors from moving any further in a particular direction?

          Keith


          At 23:39 05/10/2008, you wrote:
          >Home, or reference, or 0,0,0 can be just different names with or without a
          >calculated offset.
          >
          >
          >
          >I completely fail to understand why you state that a switch cannot be
          >accurate. Various home sensors are normally used. Here is an example of a
          >very accurate switch, much better than the mill itself:
          >
          >http://www.vinland.com/Opto-Interrupter.html
          >
          >
          >
          >Even a regular micro switch is surprisingly accurate.
          >
          >Bertho
          >
          >
          >
          >From: Will Schmit Sent: Sunday, October 05, 2008 17:47
          >I think it is important to realize that 0,0,0 (origin) and "home" are
          >different concepts.
          >
          >
          >The wild idea that a switch could reliably tell the machine that it has
          >arrived at any specific location is folly.
          >The idea that it is telling the software that the tool is "out of the way"
          >is more realistic. The best switch will never be repeatable.
          >
          >
          >
          >
          >
          >[Non-text portions of this message have been removed]
          >
          >
          >------------------------------------
          >
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          >taigtools@yahoogroups.com
          >
          >To Unsubscribe, send a blank message to:
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          >
          >Let the chips fly!
          >Yahoo! Groups Links
          >
          >
          >
        • Bertho Boman
          Hi Will, Yes, dust and dirt is a problem. That is why I have not put them on my mill yet. I am working on a protective enclosure for the switch where it
          Message 4 of 22 , Oct 6, 2008
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            Hi Will,

            Yes, dust and dirt is a problem. That is why I have not put them on my mill
            yet. I am working on a protective enclosure for the switch where it
            basically will be in a sealed environment.

            Have a great day,

            Bertho



            From: Will Schmit Sent: Monday, October 06, 2008 07:27
            Thanks Bertho.
            I have used them in the past, as encoder counters for focusing tapes in a
            huge camera I was working on.
            As you noted, they failed with the least dust they go south.
            I stand corrected.

            ----- Original Message ----
            From: Bertho Boman Sent: Sunday, October 5, 2008 4:39:43 PM

            Home, or reference, or 0,0,0 can be just different names with or without a
            calculated offset.

            I completely fail to understand why you state that a switch cannot be
            accurate. Various home sensors are normally used. Here is an example of a
            very accurate switch, much better than the mill itself:

            http://www.vinland com/Opto- Interrupter. html

            Even a regular micro switch is surprisingly accurate.

            Bertho

            From: Will Schmit Sent: Sunday, October 05, 2008 17:47
            I think it is important to realize that 0,0,0 (origin) and "home" are
            different concepts.

            The wild idea that a switch could reliably tell the machine that it has
            arrived at any specific location is folly.
            The idea that it is telling the software that the tool is "out of the way"
            is more realistic. The best switch will never be repeatable.





            [Non-text portions of this message have been removed]
          • wildhorsesoftware
            Keith, This depends upon your Limit switch configuration. Many of us just feed the Limit switch to a given Port/Pin number and let the software shut down
            Message 5 of 22 , Oct 6, 2008
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              Keith,

              This depends upon your Limit switch configuration. Many of us just
              feed the Limit switch to a given Port/Pin number and let the
              software shut down everything. In that case, the software will have
              an over-ride condition that allows you to jog off of the Limit
              switch. The danger in this is that if the software itself goes
              wacko, it may not recognize the limit switch in the first place and
              just keep driving your tool into who-knows-what.

              Others use an "intelligent" independent circuit to respond to the
              Limit switches. These usually shut off power to the controller and
              usually the spindle also, independent of the software. They usually
              also pass the Limit switch activation signal through to the software
              also so that the software knows what has happened.

              These independent circuits will have some sort of "reset" switch to
              return power to everything, allowing you to jog off of the switch
              and correct any errors.

              If you do some searching on the Internet using terms like "limit
              switch" or "cnc limit switch" you will most likely come up with
              numerous links to this subject. You will see wiring examples,
              commercially made limit switch "controllers" and DIY controllers.

              Regards,
              Gary

              --- In taigtools@yahoogroups.com, Keith Bucklitch
              <keith.bucklitch@...> wrote:
              >
              > Thanks Guys for the informative comments recently posted. I need
              to
              > sit down and read through them to determine the best way to
              proceed
              > from here.
              >
              > Just one point I am still unclear about. No one has answered my
              > query as to how one starts up the system once it has been brought
              to
              > a halt by the activation of a limit switch. Does one simply issue
              a
              > MDI command to move away from the limit position? Obviously the
              > software is still working, but is power still on tap to the
              > motors? Perhaps I have got the wrong end of the stick here. I
              had
              > in mind that when a limit switch was activated, it stopped
              EVERYTHING
              > on the machine - spindle, steppers, coolant etc. Does it simply
              stop
              > the stepper motors from moving any further in a particular
              direction?
              >
              > Keith
              >
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