In message <348EAB93.BBD47272@inficad.com>, Rusty Carruth
<rustyc@INFICAD.COM> writes
>Ok, I've got a question - I want to build a device which keeps track of how
>much energy a power-line-connected device (AC, Freezer, light, fan, whatever)
>draws over the period of a day or week or month or ...
>
>I had figured to use the toroid method mentioned earlier for measuring current,
>with some other means of measuring voltage (just to be complete and slightly
>more accurate - shucks, I could even compute power factor if I can get 'near-
>instantaneous' voltage and current measurements).
>
>I want to be able to enter our cost per KWH, connect a device to it, and come
>back in some random period of time to see how much power it used, and how
>much it cost to run (it would be nice if it also computed daily and monthly
> costs,
>based upon the measurments it took, as well)
>
>But, hey, if someone has already created such a beast, why recreate it when
>time is the important thing right now...  So - does anybody know of such a
> thing?

There was a project for doing this in 'Everyday and Practical
Electronics' Feburary/March 1996. It uses a PIC16C84 to run the device,
the software can be downloaded from their website 'http://www.epemag.wim
bourne.co.uk'.

I've built the project, it works fine! - it displays total number of
watt/hours used, and the total cost used - both of these from when it
was plugged in. The price per unit is stored in the PIC's EEPROM so
doesn't need re-entering.

It's presently connected to my fridge/freezer - it's really depressing
:-(.
--

Nigel.

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