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MetroMPG 03-04-09 02:04 PM

DIY household power use monitor / logger
Stumbled across this project - a home made logger of household power use (think: heavy duty killawatt that monitors the whole house instead of just one plug).

An AVR-based logging wattmeter


This device monitors household power usage and logs it to an SD card. A simple analog front-end amplifies the signals from voltage and current detectors and an ATmega168 microcontroller computes the power consumption using the formula P=V*I. The voltage and current are each sampled at 9615 Hz so the integration should be fairly accurate even for highly non-sinusoidal loads such as computers or fluorescent bulbs.
A bit out of my league, but probably not for some others here.
A strip chart showing power usage over time.
Our hot water heater uses over 4kW.

NiHaoMike 03-04-09 08:06 PM

How about use hall effect sensors to sense the current? Then you don't need to integrate the signal and therefore get a higher accuracy. (The magnetic field around a wire is proportional to the current through the wire, but the voltage across a coil in a changing magnetic field is the derivative of the magnitude of the magnetic field with respect to time, so it would be necessary to integrate the voltage with respect to time to get the correct current for anything other than a sine wave. But the voltage output from a hall effect sensor is proportional to the magnetic field, so no integration is necessary.)

As for other improvements, maybe add an OpenWRT router to allow network access?

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