[vdr] Re: Power consumption of Hauppauge cards

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

Hi Stefaan, all,

(sorry if this is getting OT)


> It's true that this is not the absolute correct way to measure this
> rating but it gives a overall impression which IS correct.

No, it isn't, because it does not, *can not* show spikes, which
might lead to problems. Your wattmeter has a timebase
incorperated, so it can not tell you what the maximum peak
instantainious wattage (much less the current) is. Depending
on how good your PSU is, it may well be that it can take a 150W
peak load (spike) and not complain, but then it could also be that
a 130W spike (this as an e.g. only, as yours is a 120W maximum
model) may already present a problem. Of course you most likely
will be better off with a solidly built 100W PSU than with an el-
cheapo style 150W PSU. Did you ever have a look at the old CS
Schneider HiFi stereo with some supposed 1200W? The itsy
mains transformer inside was having a good day, if it could
supply 1/8 of that. Don't always believe printed Watts.

> Indeed:
> Note on the numbers given in my previous post:

I did so, but did you read my post? 12W at 220V is only
mA. On the 3.3V line it translates into amps (which a given
PSU may or may not handle). And we do not know how the
extra wattage is divided up between the supply lines.

E.g. lets suppose your PSU has a 3.3V line that is able
to supply 10 Amps. Your setup w/o the DVB needs say 8A
(from the 3.3V line) Let us further suppose the DVB gets
all it's power from the 3.3V (it doesn't, I'm 100% sure) line.
The extra 4 amps (your 12W difference) is now overloading
the PSU,  *eventhough* the wattage rating is *not* being
overloaded. What I am trying to say is that wall wattage tells
you *nothing* about whether you are overloading a compenent
or not.

> But: is this not the only thing that counts? meaning,
> towards the anual electricity costs?

Sorry, but I don't get it. A 200W PSU will *not* consume
200W if it only has to supply 50W.

> The problem starts when using more DVB cards in 
>combination with multiple harddisks and extra DVD-RW

Absolutely. This is the reason why I told Chris NOT to go
for a minimalistic PSU.

> Fan's need power, build a fanless machine. Need extra 
>cooling, transport

Hmm, a 80mm fan running on 12V takes less than 100mA
Translates into 1.2VA. If you throttle it down on 5 or 7V,
the current will also go down. That is not going to make or
break a system ;o)) You would need 10 fans to make the
equivalent of the 12W you found. Most cases wouldn't 
even have space for  that many ;o))

>Need extra cooling, transport the heat with a heatpipe

As I mentioned a small PSU being run at or near maximum
rating will run hotter than a larger PSU which only has to
supply 1/2-1/4 of it's rated power.

I am *not* trying to flame you in any way. I just want to make
clear that it is not sufficient to find out that the DVB card is
"using" 12W of power (in your case).

Greetz,
Reinhard


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