Question was related to wiring schema I plan to use - picture available on 
this link: 
more precisely about how to connect transfer signal from torch to cramps 
1) CPC_14 and CPC_12 are dry relay contact in hypertherm plasma that are 
contacted when CNC needs to do "motion"
2) I plan to use P503_3 pin on cramps
3) first I thought I need to use 5V connected on CPC_14 but then I 
noticed P503_3 is pulled up to 5V
4) this mad me think oh P503_3 is already on 5V so it will make no 
difference if 5V will be brought and PIN will not be altered in this case
5) I decided to use GND connected on CPC_14 (I corrected schema in upper 
link accordingly).

Regarding this:
This might not work.  These pins are protected against 5V levels, but 
only have the drive capability of the BBB I/O pin (which is 3.3V and a 
few mA).  If this is not a high-speed signal, I would suggest using one 
of the low-power FET outputs.  These are "open-drain" style outputs and 
can handle voltages up to 12V. 

I use 3.3V relay and I think it has some FET embedded on it. Something like:
So I cross my fingers that BBB with few mA driving capability would be able 
to run it.

Dne petek, 07. oktober 2016 18.42.36 UTC+2 je oseba Charles Steinkuehler 
> On 10/7/2016 3:45 AM, Klemen Živkovič wrote: 
> > Oh I see on cramps schematics ( 
> > that P503 signals are 
> all 
> > pulled up to 5V so for transfer it would be better to use GND instead 
> > CRAMPS_5V. 
> Sorry, I don't really understand the question. 
> -- 
> Charles Steinkuehler 
> <javascript:> 

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