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Offline bbasiaga

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  • 3 3
limit switch issue
« on: August 31, 2009, 09:48:56 AM »
Hi all. I hope I'm posting in the right place. We are running a xylotex board with Mach 3. We set up travel limit switches on the x-axis and tested them. They worked fine. We then extended the wiring loop to include the y and z axis limits, and now we have a problem where every 30 seconds or so the software trips as if a limit was hit. It seems like there is a charge building or something and then finally there is enough potential that the point sees voltage. I'm curious if anyone has had a similar issue? Could it be something in the software set wrong? Could my loop of wire be too long and causing problems?

Thanks,
Brian
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Offline Hood

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  • 25,835 25,835
  • Carnoustie, Scotland
Re: limit switch issue
« Reply #1 on: August 31, 2009, 10:19:30 AM »
Sounds like noise, are you using shielded cable for the limits? Do you have the shield only grounded at one point and one end?
Increasing the Debounce Interval on the General configs page will help, try 2000 to see then drop back if it works. Best however to sort the problem out by shielding the wires if possible.

Hood
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Offline bbasiaga

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  • 3 3
Re: limit switch issue
« Reply #2 on: August 31, 2009, 10:37:19 AM »
It is shielded cable. I'll have to check for grounding continuity. Are you saying it should only be grounded in one place or that it should be grounded differently. I think we've brought the shielding ground back to the ground header in the control box.
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Offline Hood

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  • 25,835 25,835
  • Carnoustie, Scotland
Re: limit switch issue
« Reply #3 on: August 31, 2009, 12:36:14 PM »
Shield should, from what I understand, only be connected at one end and ideally all shield wires should be grounded to the same point in the cabinet.

Hood
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Offline HimyKabibble

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  • 1,687 1,687
Re: limit switch issue
« Reply #4 on: August 31, 2009, 04:10:20 PM »
Quote from: bbasiaga on August 31, 2009, 09:48:56 AM
Hi all. I hope I'm posting in the right place. We are running a xylotex board with Mach 3. We set up travel limit switches on the x-axis and tested them. They worked fine. We then extended the wiring loop to include the y and z axis limits, and now we have a problem where every 30 seconds or so the software trips as if a limit was hit. It seems like there is a charge building or something and then finally there is enough potential that the point sees voltage. I'm curious if anyone has had a similar issue? Could it be something in the software set wrong? Could my loop of wire be too long and causing problems?


Make sure the switches are normally closed, and you have a good, strong pull-up on the lines.  That, plus properly shielded cable (shield grounded only on the BOB end) should be quite reliable.

Regards,
Ray L.
Thanks,
Brian
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Regards,
Ray L.

Offline db1199

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  • 3 3
Re: limit switch issue
« Reply #5 on: October 02, 2009, 12:10:23 PM »
my first post. thanks for the discussion. i had and am having the same issue. actually i used twisted wire and now see i need something better. thanks again.
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Dick Bush
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