Re: usb hard drive how?



In article <ff2t26$ncb$1@xxxxxxxxxxxxxx>,
Michael Black <et472@xxxxxxxxxxxxxxxxxxx> wrote:
Hactar (ebenZEROONE@xxxxxxxxxxx) writes:
In article <ff1d2c$1j$1@xxxxxxxxxxxxxx>,
Michael Black <et472@xxxxxxxxxxxxxxxxxxx> wrote:
Leo Bing Whiteway (leobingw@xxxxxxxxx) writes:
I was given a 10 gig USB hard drive. It has a jack marked +/- and a
cable with a
USB plug on the end made to plug into a USB socket on the
computer. It also
has a USB cable.
The hard drive has:
HI-SPEED
CERTIFIED USB
USB 2.0 TM
I have no more info on it and can't find it with searching Google.
I am having no luck making it work or show up in lsusb.
Have any of you any ideas where I might look for info on how to hook
it up and
try to use it?

That +/- jack sounds like it's for an AC adaptor to plug into. I have
very little experience with USB, and none with USB drives, but I would
think a hard drive might be pushing the limit of power available over
the USB bus. Hence perhaps it needs an AC adaptor to power it up
before it will work, rather than getting power from the USB bus?

I think 3.5" drives take 12V to run the spinny-bits motor, at more
current than it can extract from the 5V@500mA that USB provides.

You're right, drives do generally need 12v in addition to 5v. But,
they will never get that needed 12v out of the USB bus, since the
USB bus doesn't provide anything but 5v.

Sure, not direcly, but there are ways to raise DC voltage. You won't be
able to squeeze enough power from USB to run the whole thing though.

I would be quite hesitant to start with 12v, for the simple reason
that if the drive is expecting less voltage, you risk doing damage.

We don't know what's inside the unit other than, obviously, the
hard drive and a USB to whatever (presumably IDE) converter. It
may run off 12v and then drop it internally for where it needs 5v,
or it may start with 5v and shift it up to 12v with an inverter, or
it may start with some completely different voltage.

The first method is a lot easier. If I were designing the case I
would probably specify 12V power, and then convert down if USB doesn't
supply enough 5V power.

As I said, I have no experience with USB drives.

Both the 3.5" USB HDs I have (different brands, bought a few years
apart in different countries) use 12VDC, 2A, same connector.

--
The powers in charge keep us in a continuous stampede of patriotic
fervor with the cry of national emergency. Always there has been some
terrible evil to gobble us up if we did not furnish the sums demanded.
Yet these disasters seem never to have been quite real. -- D. MacArthur
.