Thanks for that attachment. I assume I would need 3 of these. One for each drive. I did actually do a search for buffer, 12v/5v converter and kept coming back to Diycnc OPPV2 which seems to provide control of spindle and 12v for drives.
http://www.diycnc.co.uk/html/oppb.html Am I barking up wrong tree or just barking. Phil.