1-Wire Realtime Power Meters

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Here are a couple of circuits that can be used to measure the power used in your home or office. The first is based on the AD7751 Energy Metering IC from Analog Devices and has two current transformers to monitor the flow and return currents, this can be useful for detecting earth leaks. The output from the AD7751 (CF) is optically linked for isolation to a DS2423 1-Wire Counter, the counts are directly proportional to the rate of electricity being using, the output could be used to give either a standard usage reading like on a conventional meter, or if monitored over time could be used to easily calculate the usage in kilowatt hours.

Schematic


The second circuit is based on an Article from Circuit Cellar edition #73 August 1996 by Jeff Bachiochi, who has kindly given permission for it's use in this project. In the previous circuit we used 1:1800 turn toroidal current transformers, in this circuit Jeff used some homebrew toroidal current transformers that he wound himself, 27 secondary turns of 24-AWG teflon counted wire around a 0.75" ID / 1.5" OD toroid were used to monitor 15A, 20A, 30A and 40A circuits.

Schematic


More info and pictures coming later (when I've built it).