[TriLUG] Raspberry Pi USB hub

R Radford rradford at mindspring.com
Mon Sep 3 22:27:01 EDT 2012


The Raspberry Pi quick start guide
(http://www.raspberrypi.org/quick-start-guide) very clearly states:

"Micro USB power supply – make sure you use a good quality one,
capable of providing at least 700mA at 5V. Do not attempt to power
your Raspberry Pi by plugging it into a computer or a hub."

However, that being said, I have been running mine off of my laptop's
USB port with no problems. Depending on what is connected to it and
what you are doing, the actual power draw can be quite a bit less.
Personally I don't plan to use the HDMI or video out, and that does
cut down a lot on the power use.  I saw one site that stated power
consumption can drop as low as 350mA.  I think running it off a
powered USB hub would be okay and much safer than running it directly
off of a laptop like I am doing.  However, remember you have been
warned by the RPi documentation not to do it (but who reads and
follows documentation?).

I also picked up a cell-phone charger pack from Walgreens for $20
shown here: http://www.energizerpowerpacks.com/il/products/xp1000/index.php.
I have not done any long tests on it, but a friend of mine bought the
same charger pack and tested his for 2.5 hours of use on a single
charge.  It is almost the exact size of the RPi, and only about 1/4"
thick, so makes a great rechargeable battery pack.

On Mon, Sep 3, 2012 at 9:09 PM, James Jones <jc.jones at tuftux.com> wrote:
> Igor,
>
> The model B requires 5 volts at 700ma. I am using a Droid RAZR charger
> to supply my Raspberry.
>
> I don't think a usb hub will supply that current level.
>
> jcj
>
> On Mon, Sep 3, 2012 at 8:56 PM, Igor Partola <igor at igorpartola.com> wrote:
>> TriLUG,
>>
>> I am am expecting my Raspberry Pi board to arrive soon and am starting to
>> gather the necessary peripherals. One of the things I am looking at is
>> powered USB hubs. I am wondering about two specific things. First, has
>> anyone seen a case for sale that comes with a built-in USB hub? Ideally, it
>> would also have a single power cable for both the hub and the RPi board.
>>
>> Alternatively, if I get a separate hub, would it be possible to power the
>> RPi board from one of the ports off the hub? In other words, the upstream
>> port of the hub would be plugged into one of the two on-board ports of the
>> RPi and one of the downstream ports of the hub would be connected to the
>> power input of the RPi via an A to micro USB connector. Has anyone seen or
>> done this or can anyone say that this will not work?
>>
>> Thanks,
>> Igor
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>
>
>
> --
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