I am rebuilding my controller as part of a remodelling of my den. The computer and motion control bits will all be mounted on an ali plate, which is fitted into a 300mm wide cupboard on drawer slides.
Click image for larger version.  Name: DSC02416.JPG  Views: 160  Size: 592.8 KB  ID: 28003
Click image for larger version.  Name: DSC02419.JPG  Views: 159  Size: 670.2 KB  ID: 28004

My question is about the BoB (which plugs directly into the motherboard PP socket). In it's previous home it was a separate control box with +12v and+5v being supplied from a small (ex external HDD) power supply. As I have 5 and 12v available from the PC power supply, why not use it. BoBs give galvanic isolation with the optocouplers, but this is only necessary because using two power supplies there may be a voltage difference on the 5 volt lines, causing current flow where ther should be none.

Can anybody with a better understanding of electronics advise me about using the PC power supply for the BoB?