[maemo-developers] [maemo-developers] Measuring power consumption of 770

[From: Larry Battraw]

  Ok Igor, you finally motivated me to do some measurements :-)   All
measurements were done with a .1 ohm resistor (measured as .0924 ohms
using the 4-wire method) and a HP 3456A 6.5 digit voltmeter.  The
meter was set to the slowest (most accurate) sampling rate, performing
the calculations on-the-fly for the Ohm's law derived current.  I did
_not_ measure battery voltage, so wattage calculations are not
possible.  This shouldn't be a big deal as the current will give a
good indication of what the device is doing at the time.  I've
attached a CSV file of the spreadsheet for results.  I tried to hit
most of the use cases people might be interested in, and everything is
pretty impressive except for leaving MP3 files paused in the media
player, which consumes over 10 times the normal current while
sleeping.

Larry

On 3/29/06, Igor Stoppa <igor.stoppa at nokia.com> wrote:
> Hi,
>
> On Tue, 2006-03-21 at 11:31 -0500, ext Larry Battraw wrote:
> >   I would advocate building a dummy battery out of a piece of
> > wood/plastic with a small piece of copper clad board (split into three
> > pads) to act as the contacts of the battery.  You can then run wires
> > from those to the real battery, passing it through whatever
> > resistor/sensing equipment you want.  As soon as you try measuring
> > what goes into the DC jack you're then including whatever losses
> > incurred by the DC-DC conversion from 5V to whatever used internally,
> > as well as issues around having it potentially trying to charge the
> > battery at the same time you're measuring.  That, and Igor as much as
> > said that things could behave differently based on whether it detects
> > wall/DC power vs. battery power alone.  Honestly, at this point you
> > probably could have built a couple rigs for measuring power from the
> > battery in all the time that has been spent discussing it.  :-)
> >
> > Larry
> >
> > On 3/21/06, Frantisek Dufka <dufkaf at seznam.cz> wrote:
> >
> > > Well I was not thinking about measuring at the mains plug. I was
> > > thinking about measuring at the n770 side (5V?) because it is a bit
> > > easier then opening the device and messing with battery pins.
> > >
> > > Frantisek
> > _______________________________________________
> > maemo-developers mailing list
> > maemo-developers at maemo.org
> > https://maemo.org/mailman/listinfo/maemo-developers
>
> did anybody produce anything?
>
> I was hoping that the discussion would bring some interest to the
> fabulous world of power management also amongst other developers ...
>
> --
> Cheers,
>            Igor
>
> Igor Stoppa (Nokia M - OSSO / Tampere)
>
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