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Weird behaviour on limit switches
« on: February 16, 2018, 08:49:20 PM »
Hey all:

I am working on a new machine, and I am pulling my hair out on the limit switches.

I am using an ESS controller, running Mach 3 on Windows 7.  I have the limits set up on each axis separately, with one limit switch per axis and 2 trigger plates, one at each end of the axis.  These are S18-3005na NPN proximity switches that detect metal and run off 12v.  I have the Ess inputs pulled up with 1k resistors, and the output from each prox sensor pulls the line to ground through a diode to prevent feeding 12v into the ESS inputs.

The system is set up with X++, X--, and home switches set to the same input in Input Pin Configuration.

Everything works normally until a limit is triggered.  Then, the system seems to "Latch up".  If I manually power down and move the machine off the limit switch, on the Diagnostic screen, the "Home" indicator goes out, but the X++ and X-- lights stay lit.  The Reset button will not work, the system will not reset.  If I power down the limit switch circuit, the X++ and X-- lights still stay lit, even though the ESS input has returned to a high level and there is no longer a limit input. 

The only way to get the system to reset is to shut down MACH3 and restart it.  Then everything works normally again until the next limit event.

I don't currently have the Override configured, is this the problem?  Is the limit switch input a toggle that can't be reset without using the override?  Removing the signal from the input is not enough to be able to reset the system?

Help!

Metalguru
Re: Weird behaviour on limit switches
« Reply #1 on: February 16, 2018, 10:38:14 PM »
Hi,

Quote
Removing the signal from the input is not enough to be able to reset the system?

No. Commonly a limit event will Estop Mach. Even if you remove the offending limit signal Mach will still have to be reset manually. If you don't have "Overide Limits'
then you will not be able to jog off the limit switch.

Quote
If I power down the limit switch circuit, the X++ and X-- lights still stay lit, even though the ESS input has returned to a high level and there is no longer a limit input. 

I suspect this is a result of Mach being disabled. The sequence of events is that the limit switch triggers and Mach disables. Your description suggests to me that Mach
is not responding to new inputs until it has been re-enabled.

Craig
My wife left with my best friend...
     and I miss him!
Re: Weird behaviour on limit switches
« Reply #2 on: February 17, 2018, 07:09:37 PM »
Thanks Craig!

First, I went in and configured the Limit Override in the Pins Config to be the F12 key, but it still wouldn't allow the machine to reset.  Not sure why that's even in there, if Mach ignores inputs when it is disabled, how would that even work?

Then I discovered the Auto Limit Override in the Configuration screen, checked it, and everything was OK.

A little hairpulling for a couple of hours, and I don't have any to spare.

Metalguru