[vdr] Re: Shutdown frontend for saving power and heat

["Reinhard Walter Buchner" <rw.buchner@freenet.de>]

Hi Christian, Rene,

> > As I have pointed out before, you *CANNOT* "measure"
> > the wattage of the DVB card like that.
> > (...)
> > There is only *one* way to measure this and that is directly
> > at the DVB card using a riser / adapter card. All other ways
> > simply mean "Wer mist mißt, mißt einfach mist" (for
> > english speakers "junk in? junk out!").

> You're totally right, if you're only interested in the exact power
> dissipation of the single DVB card.

> If you're interested in the comparision of different "software power
> management" solutions, IMHO the idea of measuring at the AC-line is not
> bad.  Sure, you won't get exact values, and you can't choose a PSU from
> those (as you can't see spikes and surges),  but you will get a rough
> idea - and that's all we want for now.

Even then, you have too many factors. Rene already pointed one out.
Another would be the system itself. If you measure on the mains side,
*any* fluctuation (HDD starting up, shutting down, CRON job,
 background scan etc, i.e just about anything doing something with
the HDD, graphics card, modem, LAN, ==> simply *the* computer
hardware) will mess up the measurement. So e.g saying:

> - additionally VDR started, watching TV using transfer mode: 57..59W
> - doing the timeshift-thing: 59..60W

says nothing if the DVB card *really* consumed more power during
it's stay in the timing-shifting mode. The same goes for the other
measurements. You could smooth it out a bit if you say repeat the
measurements maybe 10 times for each situation and take an
average value.

I also don't know *what* power save really shuts down on the DVB
card. The LNB?, the tuner? the bucking step up converter? the ARM7?
etc.

Greetz,
Reinhard


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