Solved: USB bus stays powered after shutdown
We had a thread on this the other day, and the solution I implemented is slightly different than the one that was proposed.
Problem: USB bus stays powered even after Opus shuts down computer, thereby draining the battery. Secondly - I needed to power my USB hub.
Solution: I have 6 USB ports on the Shuttle, but unfortunately the 4 on the back of the computer are integrated into the board. The two front ones are not, and therefore have a cable that connects the ports to the mobo. Here - we spliced in a relay for the two USB ports (splicing into the power lines) that is powered by the molex connector. So - power is supplied to the bus only when the hard drive (for example) is powered. In essence, as soon as the computer shuts down, so does power to the bus. The second relay is essentially the same, except that it's for the 5v line that runs from another molex connector to the USB hub. So - power is supplied to the hub only when the computer is on.
It's essentially like the solution that was drawn up on the other thread, but note that no diode's, and therefore no drop in voltage, were necessary to do this. It works like a charm.
Thanks for all of the help and suggestions.