Powering USB port

[geniejhang]

Hi.

I've recently bought a Raspberry Pi model B rev2(?), I think, and HITACHI 1.5TB 2.5" Touro external hard drive.
I tried to connect it on RPi, but it sounds tick tick every time I access. Still, it works, though.
I think it's because of the sudden drop of voltage or insufficient current to USB.
(External HD is ok. It works fine with my Mac.)

So. I've looked through the schematics of RPi.
( http://www.raspberrypi.org/wp-content/u ... .2_027.pdf )
And come up with that if I short 1 of F3 and USB VCC, in my naïve thought, it will perfectly work.

Is it dangerous?

Thank in advance.
Bests.

[FTrevorGowen]

Hi.
I've recently bought a Raspberry Pi model B rev2(?), I think, and HITACHI 1.5TB 2.5" Touro external hard drive.
I tried to connect it on RPi, but it sounds tick tick every time I access. Still, it works, though.
I think it's because of the sudden drop of voltage or insufficient current to USB.
(External HD is ok. It works fine with my Mac.)
So. I've looked through the schematics of RPi.
( http://www.raspberrypi.org/wp-content/u ... .2_027.pdf )
And come up with that if I short 1 of F3 and USB VCC, in my naïve thought, it will perfectly work.
Is it dangerous?
Thank in advance.
Bests.

I would not recommend shorting F3, given that that polyfuse forms part of the Pi's "protection circuitry" against GPIO wiring faults etc. (You will also probably invalidate any warranty doing so) USB HDD's are best powered externally either via their own PSU or a powered USB hub. An alternative is to use one PSU to power the HDD and (back-power) the Pi via the main USB (output) port or GPIO connector so long as you also provide over-voltage and over-current protection - this method again "by-passes" the on-board protection but does not require "board modifications".
Trev

[geniejhang]

I would not recommend shorting F3, given that that polyfuse forms part of the Pi's "protection circuitry" against GPIO wiring faults etc. (You will also probably invalidate any warranty doing so) USB HDD's are best powered externally either via their own PSU or a powered USB hub. An alternative is to use one PSU to power the HDD and (back-power) the Pi via the main USB (output) port or GPIO connector so long as you also provide over-voltage and over-current protection - this method again "by-passes" the on-board protection but does not require "board modifications".
Trev

Thank you for your replay, FTrevorGowen.

The last thing I thought is solder a wire on 1 of F3 and
cut the USB cable from the HDD and connect the power cable from HDD inside USB to the wire soldered on 1 of F3.
Do you think this will work?

[Lob0426]

I increased F3 to 1.1A from 750ma. This worked for a couple of my 2.5" drives. It did not fix all of them. All work with a 4 port hub and a 2A PSU.