Limit Switches work in NO but not in NC


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Thread: Limit Switches work in NO but not in NC

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    Default Limit Switches work in NO but not in NC

    After changing limit switches from NO to NC (which is the better method) I get limit switch tripped in Mach 3. I did change port/pins for each axis from active low to active high by unchecking. Prior to this all limits functioned fine when using the NO connection on the switch and the ports and pins were set to active low. I've gone through each axis turning it off in port and pins to see if there was a specific one causing the issue which didn't give me any idea as the same issue occurs with 1 or all 3 active. Of course with all disconnected in ports and pins there isn't a trip happening.
    I've checked all inputs and there is 5v present which is expected as the switches work fine in NO.

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  2. #2

    Default Re: Limit Switches work in NO but not in NC

    Some breakout boards will only pull one way. Others need to be jumper or switch set.

    Bob La Londe
    http://www.YumaBassMan.com


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    Default Re: Limit Switches work in NO but not in NC

    Normally open switches need to wired in parallel.

    Normally closed switches need to wired in series.

    Did you change the wiring?

    Don



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    Default Re: Limit Switches work in NO but not in NC

    Hello Don,
    Yes I did do a rewire in series with no difference. I ran the input to NC of the first switch, jumper-ed from common on that switch over to the NC on the second switch. From the common on the second switch I ran back to the ground on my junction block. I've seen different examples for series wiring. One is as I've shown here and the other was to NC then from that common over to the other switch common then back to ground from the second switch NC. I've tried both configuration. This is my first cnc build so I'm sure it me and understanding.

    Andy



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    ........After changing limit switches from NO to NC (which is the better method) I get limit switch tripped in Mach 3.

    Can you increase your debounce settings for those inputs? I've Seen many switches that will cause false alarms when in NC operation. Seems the contacts vibrate in them during motion. Raising debounce usually fixes that scenario quickly.

    Chris L


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    Default Re: Limit Switches work in NO but not in NC

    This may not apply but some interface boards require 12 to 24 volts input to run e-stop, probing and limit switches. There is a 10 volt regulator and that is what you should see. The interface board is very common and has a relay on it.



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Limit Switches work in NO but not in NC

Limit Switches work in NO but not in NC