Contactor and Mach Estop...
 

I was thinking..... why not use the other set of contacts on the contactor (t3/l3) to stop Mach3 when the EPO button is pushed.

This would be a simple loop over to the pmdx and back, closed when machine is powered up/open when epo/off is pressed.

BTW, I am using the teco contactor from Factorymation.

Stan

Opps forgot to mention that this is 115v wiring...

Although this would work, it mixes high voltage and low voltage wiring at the same device. It does so at at a device that uses a strong alternating magnetic current in close proximity to the wires - the coil that activates the contactor. That's noisy. Also, from the perspective of a low voltage circuit, the contactor is likely to "bounce" - send several on/off/on/off/on pulses when it is switched on.

So, you run the risk of (A) a wiring error taking out every low voltage device in your system, and maybe the computer as well, and (B) noise from the contactor coil causing Mach3 to think there was a shutdown when there wasn't.

I think I'd be inclined to solve this problem on the low voltage side, which should also get shutdown by the EPO anyway, right? You just need to sense when the motor power supply shuts down. Depending on your overall wiring, there should be a number of opportunities to grab this and interface it to your PC; for example, if you use proxy sensors, they too may shutdown when the EPO kicks.

I would NOT wire a contactor in the manner you are suggesting.

I had thought about issue of the close proximity to the ac contactor as well..

I also thought of wiring a second loop around and through the epo/off switches using a second switch block. This would be 24vdc through an isolator circuit before the pmdx.

Mach is going to "brown" out when the 5vdc supply drains and the chargepump (on the pmdx) quits responding.

So I might be working/worrying for nothing.

Stan, you are worrying over nothing but it's just normal. ;)
Once you get you hand at it, you will understand why most of us layout the cable the way we did.