NC limit switches

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DG Acheron
Posts: 2
Joined: Sun Apr 15, 2018 6:42 am

NC limit switches

Post by DG Acheron » Sun Apr 15, 2018 7:18 am

I know that this has been raised before but IMO Normally Closed switches are a more fail safe configuration than Normally Open. In the event of a broken wire or switch a NC circuit will alarm and stop everything whereas NO will keep on going regardless.

I have set up a CNC lathe with Y axis assigned to the rotary. I modified the config.h and the hard limits and homing all worked well using NO as recommended. I then changed the configuration to NC on the X and Z axes and set $5=1. The hard limits worked correctly however homing did not work. I tried tying the Y switch terminal to ground but it made no difference.

I notice there are a few other items I can try in config.h and I can disable the internal pull up resistors but I am reluctant to make random changes.

Any thoughts?

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