kill a watt?
James.P.Lux at jpl.nasa.gov
Thu Mar 13 13:22:15 EST 2003
At 09:36 AM 3/13/2003 -0800, Jim Meyer wrote:
>On Sun, 2003-03-09 at 16:35, Jim Lux wrote:
> > Sure, it'd be nice if it had an external interface, but then it would cost
> > $500+, if only because it's a line connected device, and you'd have to
> > provide isolation, etc. There's a web site out there where someone took it
> > apart... everything is floated at line voltage inside (which makes it muy
> > cheap) much like X-10 stuff.
>Heck, at the $45 price RGB noted, you should point a cheap webcam at it,
>take pictures at some reasonable interval, and write a script to OCR the
>pix and parse the output for monitoring.
>But maybe I'm just geeking for the fun of it. =]
Actually, this is a really good idea... the web cam is $20, the Kill-a-Watt
The only problem I can see is that you might need to push the buttons on
the Kill-a-Watt to cycle through the modes.
Another inexpensive approach is to transformer couple the current and
voltage on the line into the L&R ports on a sound card, grab a tenth of a
second of data, and do all the power quality calculations you want. If
you've got three phase power, you need 6 or 8 channels, which makes it a
bit trickier.. but you'll be able to see if you've got circulating harmonic
currents, etc. Anyone ever synchronized multiple sound cards across a cluster?
The current transformers are $20, the voltage transformer is $10 (brand
new, Qty 1 prices.. surplus can do MUCH better)
James Lux, P.E.
Spacecraft Telecommunications Section
Jet Propulsion Laboratory, Mail Stop 161-213
4800 Oak Grove Drive
Pasadena CA 91109
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