Originally Posted by
Doddy
Problem sounds to be sporadic - unlikely to be something that can be diagnosed with a meter.
@Nr1: The things I'd look at:-
Sounds like you have potentially two problems - one of UCCNC registering an input when the input is inhibited?, that's my understanding from your description - and I'd try to resolve that first. If the e-stop, inhibited in UCCNC, is ignored from manual activation of the e-stop (i.e. it looks inhibited) but you're still getting random e-stops through, then I'd suspect the UCCNC software. Could you knock-up a Mach3 build and see if you get similar?
If, however, having inhibited e-stop in UCCNC, the e-stop control does work as you'd normally expect then clearly this is a configuration/software bug issue - try rebuilding your config etc (I've not used UCCNC outside of demo mode so don't know how easy this is?) - or, again, trial a Mach3 build to resolve if it's a software issue or not.
The other problem sounds like the sporadic triggering of the e-stop at an electrical level. Try to understand the software issue before you waste hours on the electrics...
You have two main signal paths: Control-to-the-BoB, and BoB-to-UCx00. The first path - it sounds like you've tried to address EMC/noise (though there can still be gotchas there - are you grounding the screen only at the control box side?, internally to the control box have you shielded that cable?). You could switch to 24V signalling by including a current-limiting resistor between the e-stop line and the BoB input - that would improve noise immunity, or put a (say) 1k resistor between the BoB input and ground to bleed any capacitive induced EM. I personally think this is unlikely to fix your issue.
What about the BoB-to-UCx00 - are you using the provided unshielded IDC cable (26w IDC connector, 25W D-Type IDC connector, 30cm of cable between)? - when I build up my control box I *will* be cutting this cable down to a minimal size to reduce the effect of cross-coupled signals from UCx00 outputs and UCx00 inputs. The UCx00 inputs are reasonably high-input impedance (though a 4k7 pull-up to 5V on board) - it's possible to get short pulses from the stepper outputs coupled to an e-stop input. Have you tried changing the e-stop input? - e.g. Input #13 on a port 2/3 is physically as far away from the stepper outputs on the IDC cable - cross talk should be minimised here. By grounding input #12 as well you're providing the best isolation for your e-stop as you practically can. Worth a shot to see.
Other ideas - try de-powering your spindle - and air-cut - see if that improves things - will indicate if your problem is EM related. Similarly, disconnect the outputs from the BoB to the Stepper Drivers to see if that affects it (causes: EM, or noise on the PSU lines).