Building a case from a external disk case

[jcrawford]

Sorry, I cross-posted this from the Interface forum. If the if the board god could remove the posting in the Interface forum I would appreciate it.
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I need some help in the decision process about the electronics. The power supply is marked 12v and 1a/2a/3a/4a it plugs into a small circuit board that among other things has power and data connectors for a SATA drive. It appears to me from pin outs for the SATA power cable that I can pull 5v in at least 2 and maybe 3 spots on that connector.
I propose to use one spot to power the Pi and another spot to power a USB hub.
Any help in deciding whether this will work with out frying the Pi or the USB hub would be greatly appreciated.

[Dilligaf]

Not sure without knowing the exact unit but most external disks have a power brick that has both 5 and 12 volt outputs, you would probably be better off taking 5 volts directly from where the supply plugs into the case rather than from the sata board.