Fri Jun 29, 2012 1:51 pm
I've done something along these lines (sorry, no diagram or picture yet).
I have a 5v 2000mA PSU that used to run a wireless access point.
On a piece of stripboard I have mounted 5 usb sockets (two double sockets and one single. The 5v lines of all of these sockets are connected to the PSU's 5v line. All grounds are connected.
Two of the USB sockets have their data and 0v lines connected to USB cables (from dead USB mice), which are plugged into the Pi's USB sockets. There is also an LED to indicate power is on.
The Pi's USB power lead is plugged into one of the other sockets.
So, I have 2 "active" USB sockets, and 3 "power only" sockets. I can happily plug in any two USB peripherals I like, including a USB powered 2.5" disk drive and a USB powered DVD writer which has a "Y" cable and takes one "active" and one "power" USB socket.
Like your design, no power is taken from the Pi's USB 5v lines and I can connect a powered USB hub without worrying about it feeding power back into my Pi.