Raspberry PI Power

[Colin McGregor]

On Fri, Aug 2, 2013 at 3:42 PM, Scott Allen <mlxxxp-Re5JQEeQqe8AvxtiuMwx3w at public.gmane.org> wrote:
> On 2 August 2013 13:39, William Weaver <williamdweaver-Re5JQEeQqe8AvxtiuMwx3w at public.gmane.org> wrote:
>> I totally agree that it's easier to measure the Voltage than the current,
>> the problem is for the situation the RPi is going to keep the voltage
>> constant on the 5V rail.
>
> No. The RPi requires a regulated 5V input. It's up to the power supply
> to keep the voltage constant at 5V regardless of the current draw. If
> the RPi and whatever else is being powered requires more current than
> the supply can provide, then either the voltage will drop or the power
> supply will blow a fuse, shut down, or burn out, depending on the
> supply's design.
>
> Thus, measuring the voltage under full load is a valid way of
> determining if the supply can provide adequate current. Note, though,
> that using a meter to do this won't show any ripple. It's possible
> that under high load the ripple voltage on the supply will be out of
> tolerance and cause problems. You would need an oscilloscope to show
> this, but the same goes for current measurements.

Well... Times that an oscilloscope would be useful to me only happen
once in a blue moon, and with a price even for a VERY basic
oscilloscope (such as the one designed by our local Peter Hiscock)
being almost $200, well I just can't cost justify that when diagnosing
(note, diagnosing, not fixing) a problem with a $35 (US) computer...

Nice thought though. Anyone with a Raspberry PI and an oscilloscope
want to take a crack at this?

Colin

> --
> Scott
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