[cyberkeith]

Have been using my CNC Router for a few months now, no major problems until...
I grounded the frame of the machine to add a Touch Probe.
Right away the limit home switch start throwing false signals every few seconds.

I did several hours of reading here and testing and I am still confused.

Did have 3 limit switches wired series (normally closed) and shield grounded at controller
also 3 home switches wire Open and shielded. Changed these to use one input on the BOB for the probe.

Ended up trying all switches in one loop normally closed
As soon as I ground the machine, it false triggers within a few seconds.

So I tried wiring all the switches Normally Open, grounded the machine and everything works fine.

I really prefer having a closed loop switch system, and from what I read it sounds like most false triggers happen on a open loop system.

So why do I get the trigger on a closed loop?

I run two power supplies and the motor cables are long and un-shielded.

Just not understanding something here. I do have 1.36 volts between the machine and ground.


Thank you in advance, Keith

[DonKes]

Put some capacitors across teh circuit.

Research to find the size - there are some discussions here. Make the time constant appropriate for the step rate.

Don

[Dan911]

I'm no pro but just finished setting my limit/home switches up after allot of research. I did the loop system with normally open and active low. Works great after raising the debounce interval to 500.

Dan

[cyberkeith]

Thank you both Don and Dan for the input.
I have tried capacitors in several locations with no improvement.
Your way Dan seems to work for me right now. I just ordered shielded Motor cable last night and will replace all those lines.
Since I had to buy 250 feet of 16/4 now I am looking for something else around the house to rewire....ha ha

Keith

[DonKes]

I forgot to say I used both methods. A lot of debounces did not help much until I added the capacitors.

Don

[Dan911]

Thank you both Don and Dan for the input.
I have tried capacitors in several locations with no improvement.
Your way Dan seems to work for me right now. I just ordered shielded Motor cable last night and will replace all those lines.
Since I had to buy 250 feet of 16/4 now I am looking for something else around the house to rewire....ha ha

Keith

Not my way, I learned from others who posted here. I didn't write in first post but I used shielded cable and grounded shield at each end. Glad I was able to help sorting your problem out.

Dan

[wizard]

That 1.36 volts between machines could be very significant. Also consider moving to 24 VDC I/O as that can provide noise immunity through optical isolators. Review all grounding in the machine. Make sure power cabling and signal cabling are separated and never run them parallel to each other.