[off-topic] Powered USB Hub

[Leon Wright]

On Thu, Feb 14, 2013 at 10:19 PM, Milan Pospisil <pospim at gmail.com> wrote:

>           Generally speaking two voltage sources of uneven voltage
> connected together will create flow of current. (or electrons, whichever
> way you want to look at it) And of course, the nominal voltage between
> those two will be the result of the difference between those two potentials.
>  Say for example that the output of your Raspberry Pi is 5.0 Volts, and
> the connected external power source (the USB hub) is 5.1 Volts. Thus the
> resulting voltage(the difference of potentials between them) will be 5.1 -
> 5.0 = 0.1 Volts, or 100 mV and the resulting current trying to flow inwards
> will be given by this voltage and the internal output resistance.
>  In this case 100mV does not represent a great deal of power, but should
> the difference rise to several volts or more, than of course that might be
> a reason for concern. The manufacturers are aware that this can happen and
> most power supplies have inbuilt protective circuitry.
> However, that is only in general, as I am not familiar with the R-Pi
> arrangements, perhaps someone else might want to comment here specifically.
>

Good explanation Milan! I believe the later revisions aren't as sensitive
and from what I gather voltage drop is a much bigger issue with stability
than a small amount of over voltage.

Leon
--
DRM 'manages access' in the same way that jail 'manages freedom.'

# cat /dev/mem | strings | grep -i cats
Damn, my RAM is full of cats... MEOW!!
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