I'm not quite sure if its relevant in your case, but do be careful with alternative ways to power the PI, if you "backfeed" it, or use any power entry method other than the micro-USB input then you are effectively bypassing the PI's Polyfuse, which also means that if ever the overvoltage protection diode D17 triggers, and you power the PI with a PSU able to deliver much current that isn't itself fused, D17 will possibly go up in smoke (as its not protected by the fuse) and will cause a permanent short of the 5V supply!gelfling6 wrote:I have one I got a 7-port hub at Staples, (with their label) which came with a 3.0-Amp supply, and the 7-port Dynex (Best Buy) hub I modified slightly for the Pi. (soldered the wires for the power cable directly to the coaxial socket , It freed-up a whole USB port!) which came with a 3.6-Amp.
As long as you have a 1-Amp minimum supply, which the Pi seems to want (anything less, you seem to be losing voltage because of too much draw), you're fine, but it's the Pi, combined with anything else running via the USB, that's going to chew-up the amperage. (and yes, the Keyboard & mouse do!)
I have the Gear Head 7 port powered USB which says gives some problems according to the website. I've noticed that the 4th and 5th ports won't communicate with the Pi unless the sources themselves are powered. For example, if I plug in a USB flash drive, it won't mount or be recognized on the Pi; but, if I use a powered Ext HDD, it mounts and reads just fine. Now, the same USB flash drive will mount and read just fine on the 6th and 7th ports just not the 4th and 5th.Mobius wrote:Check out http://elinux.org/RPi_VerifiedPeripherals
Specific items mentioned here may not be available where you are located. You will want at least a 1000ma supply but be advised that not all USB wall supplies output within the acceptable range. Fortunately, most of them are close enough that the Pi input circuitry will clamp it to 5 volts. The polyfuse is supposed to open if the voltage exceeds 6 volts and there is a 5 volt zener diode that is supposed to limit the voltage. Some 7-port hubs do not work properly even if their 4-port version does (check the link above). Try to get a powered hub to offload some of the current requirements of the Pi. I found my power adapter at a thrift store and my 4-port hub is by Gear Head. Got it at a Walmart store but then I live in the states.