Step 1: Intro
Hi
I recently got a Raspberry Pi to use as a HTPC running Raspmc.
But came into problems where the Rpi does not provide enough bus power on its USB ports to power a 2.5″ external harddrive.
So I decided to add a external 5v power supply to provide power to a hub with its own switch.
I am using the USB port on the TV to power the Rpi and a 5v 1000mA to supply the hub with the harddrive attached..
This is what i did..
Step 2: Requirements
For this Instructable I have use bits and pieces that I had floating around the house..
All that is needed is a:
Powered hub
Toggle switch
Some heat shrink tube
A few pieces of wire
Soldering iron
Some DC male/female connectors
And a 5v power supply (1000mA is enough)
Step 3: Take Apart
I removed the cover for the hub and removed the DC jack connected to the circuit board.
Just to be safe check the polarity with a multimeter by taking a Male DC jack and testing for continuity on the +5v line and negative rails on the board its self.
With the hub I am using there are 2 Negative (Far left and far right pins) and the center pin is +5v.
Step 4: Add The Switch
Then solder the toggle switch in between the +5v line and the board.
Connect the negative straight to the board. ( The board had 2 negative pins so I made a small Y-split)
I have used a male usb cable to power hub so it can still be used on a computer. (I cut the green and white data lines off so it’s just the 5v+ and negative ) 
Step 5: Test
After I tested to make sure nothing was shorting and the switch works I put it all back together..
(There are now 2 switches on the hub. The original is to turn the actual ports off and the added toggle switch turns on the main power)
For more detail: USB Powered Hub Hack For Raspberry Pi External Harddrive
