Quote Originally Posted by JAZZCNC View Post
Ok don't want to send this thread off course too much but think best to clear this up so not to confuse.!!

Yes I under stood what you meant but don't think you did me.? I wasn't suggesting sending 24V up the PP's chuff.!!

The 24V supply has multiple uses.!!. . . It's sent thru the limits Switch's and E-stop to help with switch bounce and noise. This is done in conjunction with 24V relays, so it powers them has well.
These control the 5V signals from the BOB, they also act has safety for other things killing power to anything attached etc, enabling a hardware driven fully safe latching E-stop system that can only be restarted when in a safe condition and the master relay engages even then this only engage after pushing a reset button.
If any of the safety switch's are tripped or some things in an unsafe condition then nothing happens.! . . . . Also In this case and the point of my comment meant to also use it to power the BOB and therefore save messing about with the 5V from HDD.
I understood you perfectly well hence the reason why I said "I'm sure your PC wouldn't want you to put 24v or more up its paraport",
Whatever vendors BoB is used, assuming it is capable of complete opto-isolation, and you wish to maintain it, the PC side will almost certainly need to find a logic 5v since most paraports can usually sink far more current than they can source.
I realise I mistakenly suggesting the e-stop be routed back into the PC - Bad move to rely on S/W for that function!. If I did mislead anyone I apologise.