[geeks] New Intel Atom-based barebones system

[Jonathan Groll]

On Wed, Aug 20, 2008 at 10:00:59AM -0400, Sandwich Maker wrote:
>" From: Jonathan Groll <lists at groll.co.za>
>" 
>" > []
>" 
>" I *think* my weird method of measurement measures VA, but that
>" assumption may be false! Luckily, no one on list has commented on
>" it. (I measured DC current on my multimeter since it couldn't measure
>" AC, and had to use a bridge rectifier)

If I'm measuring DC, then could I assume that 1 W = 1 VA?

>" > []
>" 
>" What sort of power factor (ball park) do computer power supplies have?
>
>they're all smps these days, so i'd expect
>1. the first component after the power plug and protection components
>   is probably a bridge rectifier
>2. probably no big filter caps
>3. the pf is probably close to 1.  i'm not sure they could claim the
>   high efficiencies at all power levels they do with a low pf
>
>your measurement scheme could be quite accurate.

This wikipedia page:
http://en.wikipedia.org/wiki/Switched-mode_power_supply

says: "An SMPS designed for AC input can often be run from a DC supply
(for 230V AC this would be 330V DC), as the DC passes through the
rectifier stage unchanged. It's however advisable to consult the
manual before trying this, though most supplies are quite capable of
such operation even though nothing is mentioned in the
documentation. However, this type of use may be harmful to the
rectifier stage as it will only utilize half of diodes in the
rectifier for the full load. This may result in overheating of these
components, and make them fail as shortcircuits"

So if you are thinking of trying my technique be aware of these
caveats.  For the record, I live in a country with 220V mains.

Cheers,
Jonathan.