Hi Andrew, I like the yogurt container! Something like that would get Homeland Security or the marijuana cops out in a minute around here. I wonder if there is a commercial product. I guess the current transformers are the way to go. Thanks. Cheerful regards, Bob On Tue, 11 Mar 2008 22:59:41 +1300, "piclist" said: > I've been researching this kind of thing for a while - the most > successful optical version seems to be where the meter has a LED > flashing n times/kW - a simple light-sensor can count pulses. > > There's a couple of examples where somebody's watching for the black > stripe on the disk to go past, but I don't know how successful it can > be. I watched mine for a few minutes, and the disk speed is so variable > that it seemed to be too inaccurate, especially when the rate is slow > i.e. it could be speeding up/down without getting round past your > detector. It can take anything from minutes to fractions of a second > for the disc to complete a revolution... > > One guy made a disc watcher out of a laser pointer (no details though): > > http://www.telusplanet.net/public/jacobs2/jake/projel/pwrmtr/ > > I toyed with the idea of using a light sensor this way, but the > mechanics of attaching it close enough to the meter without upsetting > the meter man didn't get upset were beyond me! > > I've gone the current transformer route - much simpler (once I found out > about split-core transformers :) )... > > Andrew -- http://www.fastmail.fm - Access all of your messages and folders wherever you are -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist