Just a thought...I fabricated the control box of wood, thinking it might provide some resistance to noise...maybe the problem rather than a solution.  I grounded the cable to a ground terminal in the board...a little reduction but still resets every 3-4 minutes.  Currently, the only thing that is not grounded is the drives (he power supply is grounded with the input voltage cable).  Is there any sense in replacing the switches?

thanks
geo

When you say you grounded to a Gnd terminal, are you meaning a Gnd on your breakout? If yes then they are not the same thing as the shield should go straight to a terminal that is connected to what we here in the UK call Earth.
Hood

First let's call the shield and it's bare cable a "drain". This needs to be connected to a star ground (this is also where the ground of your AC supply should terminate. This will be connected in the controller cabinet only, not on the machine side. Connecting the shield on both sides will cause ground loops. This connection is only to drain the stray signals. This is how I have come to understand it. A separate wall wart to provide the necessary voltage seems to be better than sharing a supply.

I have now grounded the power supply (with the ground from power source: a 2/12 w/ground power cable),  I  have run a chassis ground from each drive to the same ground as the power supply.  I have also grounded the machine frame to the same ground.  The breakout board is grounded with the power source (USB shielded cable with ground) of it's own.  Noise still rules....still resets.

I used a meter to check the continuity between all units in the system.  There was an unusual signal from the main power supply to ground:  the signal pulsed rather than continuous sound....must be the source of the noise.  None of the other components produced the pulsing sound.  Maybe a metal housing just for the power supply might help?

thoughts?
thanks
geo

  Have you run your limit switches successfully (not as home switches) with a low (under 250?) or "0" debounce setting? 

F1 has a good point here and I don't see where you have verified that the machine will or will not fault when running without the homes enabled.
Other than vibration, if the machine runs OK this way it's likely not noise, more like just really crappy switches.

What is the brand/make ?
New or used ?

Just thinkin'

The only way it runs without fault is to disable the limit and home pins.  I have attached a external power supply to the system and can make it run with the debounce set @3500....not so good.  I am in the process of adding ferrite cores to all cords, cables and driver feeds.  I am also building separate housings for the power supply, drivers and breakout board.  The micro switches are not expensive and not cheap.  I think my problems are related to other components, but if all else fails, I will invest in shielded switches. Any suggestions on the switches....I don't want to buy them twice...thanks
geo
 

One other possibility.
 I had a cnc4pc board that had 1 goofy input pin.
Did similar to what you're describing. Even with the pin configured but nothing connected to it, it would fault out.
Changed to another pin and it ran with debounce at 0.
Might try that if you have another available input pin, and it's easy to access.

I presumed that the shield (ground and alum) in and of themselves would divert noise

The shield can keep unwanted  noise out or it can also keep noise inside and the intent is to provide a low resistive
ground path. The shield is connected to a different / specific ground path. Shielding varies from 100% to lesser amounts
the amount varying based on intended use. Once noise, and i will use that term loosely, is mixed with the signal it can be extremely
difficult ( even impossible) to remove . The noise may take the easier path to the ground.

Just high level tid bits......FWIW,
RICH

Go figure...I changed the pin on the limit and home switches and guess what....debounce @ 50 and NOT ONE RESET.  I think I'll declare victory.  Putting the original power supply back and see what happens....thanks to all.
geo

Great to hear. Hopefully it will work well. What happens at 0?