While I do think that the lowcost powered USB hub would be the better choice, checking the USB disks I have lying around here, it looks like the small ones that use laptop drives internally all run off of 5VDC to 5.1VDC miniature switching wallwarts. Current of these three wallwarts (I have many small USB drives in the office, but only three came with the wallwarts) is 1A on the minimum side and 2.2A for the largest capacity one. Maybe that can get you started finding a wallwart in your grab box. Be sure to have the correct polarity on the plug tip. FWIW, the ones I have look like they were probably originally designed for cellphone charging or the like.

The USB spec for power is 5VDC at 2 Amps. This should be enough to power any of these drives. The problem comes in when motherboard mfrs or their designers don't actually provide the full two amperes of current at your machine's USB socket. I've never investigated with the test equimpment, but I'd bet they are using Current Limiting resistor in series with each socket and because they didn't want the expense of doing it right, with "proper" regulation at each socket separately instead, the current the socket is able to supply is dependant upon the DC resistance of the device in question. The hard drives, having to spin the motor and move the headarm, are likely a lower resistance than most other devices and thus load the voltage down on the socket side of that cheap resistor. The scenario makes electrical sense but as I said, I have never opened up a mobo on the testbench and proofed the theory. However, the fact that having two connectors at one end of the cable, and that only one of those connectors has the actual Serial connection wired through to it while the other is just the two 5VDC lines in parallel pretty much tells the story to anyone savvy in the art of electronics.

Can't see 'em doing anything else, though. And that is customer driven not some manufacturing conspiracy theory. See, you guys and gals are always wanting to pay the lesser price. If one company puts out the thing for less money and it "appears" to be "the same thing" then you get what you pay for. Meanwhile, the poor engineer who designs the USB power ports *properly* with a separate 2Amp voltage regulator circuit for each one, ends up getting yelled at or laid off because his company didn't sell the boards that cost more money.

And that's the way it is.


--Mac

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