Eliminate potential for hazardous limit switch set-up

Shapeoko’s proximity switches are NO which presents a potential hazard if one of them is broken or if one of the wires somehow pops out (or is cut, etc). The computer won’t detect this since the circuit remains open. I found this the hard way when one of my new induction proximity switch crimp gave way.

An easy fix is to have normal behavior changed to NC. This way any fault will open the circuit, thus stopping the machine.

Obviously, this means that all the switches would require replacement on existing machines, but if this is made as an option in the Carbide Motion setup, existing users would have the opportunity to stay with their NO set-up, or change to the safer NC switches.

My understanding is the problem with NC is that since it requires a continuous input it’s more prone to interference and false positives.

The Carbide 3D switches are for homing only, so arguably, only need to be reliable when one initiates a homing command (or tool change, or probe operation) and is in a position to intervene if something untoward occurs.

True, the NC would need a constant current, but it would only measure continuity, no PWM or fancy sensor data, so there should be no interference. The only positive would be when the wires are shorted. In that case resistance measurement could be used, but that would get into the “fancy” way to implement this.

I do understand that the switches are for homing, but as you noted, for probing as well. The only intervention available, if there’s a problem with a switch during probing, even with the operator alert, is to Estop, which would abort the job since the position is lost on whatever axis the switch faults.

Having the option in the set-up would be great IMHO. Not a deal breaker, just a suggestion that would have helped with my faulty connection.

As far as settings go, you’d just need to set $5 = 1.

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