Turning on the lights trips a limit switch

[fullacott]

I have just installed a SS to replace the parallel port connection on a retrofit mill which had been running for 5 years or so. SS installation following WARP9 and Jeff Birt's guides was straightforward (thanks for those) and I have been very pleased with the change. Except that if I turn on a mains neon light or turn off a small machine elsewhere in the workshop I get a "Limit switch tripped" message and flashing red restart button.  What is curious is that it only trips the Z axis and if I disable the limit switch lines in Ports and Pins for the Z axis all is fine.

So, next I swap the Z and Y inputs from the microswitches and still get a Z trip. That seems to tell me that the connection and screening between the microswitch and the control cabinet is OK. Presumably the fault lies between the socket on the control cabinet and the PC.

I use a limit switch circuit suggested by Mark Vaughan in this forum with 24V supply to the limit switches and optoisolators controlling the 5V inputs to my C11 break-out board. This has worked with the parallel port set-up with no problems for some years.

I have rewired all the Z axis part of this limit circuit with new cable, screening grounded at one end to a star connection on the cabinet.

The SS is mounted on an insulated board within the cabinet and connected to the adjacent C11 with the supplied ribbon cable.

I am obviously missing something and would be greatful for any suggestions. Peter

[thosj]

Might be noise. Go in Mach Plugin Control, SS plugin, and put some debounce (or whatever it's called, lower right of the window) in Home and Limits. Try 250 or 500 or something and see if it fixes it.

I'm not sure how much is "too much", but if you go too high, it'll have the opposite effect and the switch will stay the other way!!

[fullacott]

Thanks Thosj. Filtering certainly masks the noise. I knew that debounce in Mach did not effect SS and had missed the filter section of the window on setup which sounds a bit dumb but I was rushing to get it up and running as one does.

[7654321]

I have same problem on z axes... limit switch trips as soon as i jog.

[7654321]

did you replace the ss usb cable?

[fullacott]

did you replace the ss usb cable?
Yes, but it did not help. I have read posts elsewhere about USB cables which are too "thin" to carry adequate load. I don't think that was my problem, I am using a separately powered break-out board and the Smooth Stepper has just one port in use at the moment.

I have same problem on z axes... limit switch trips as soon as i jog.

Hmm. I am not sure it is the same problem but it could be similar. Mine originated outside the system. While initiating a jog might be causing the limit to trip because of noise associated with  the stepper motor it could also be something within the control circuits. If you are using a SmoothStepper, does setting a filter delay on the home or limit line in the SS setup have any effect? It has overcome my tripping although, obviously, it has not removed the cause of the interference. In my case a setting of 200 was enough to do the job.