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Executive Summary
Today, more and more consumers are looking to “go green,” and the practical tools that
inform their decision-making are of increasing importance. One of the areas in which
individual consumers impact the environment most is household electricity consumption.
Tying these two ideas together, we set forth to design a low-cost household power-usage
data collection network.
The purpose of this system is to allow a homeowner to centrally meter energy data from
all the home's outlets at once. Small power metering devices (referred to as "minimeters")
can be attached to or built into each outlet in the home. Mini-meter data can then
be transmitted to a central computer for processing via power-line communication
network. A computer program outputs a spreadsheet that lists all the household energy
data for the homeowner to peruse. All the technology necessary for such a system has
been developed – our challenge is to fit the pieces together for our specific needs.
Considerations include the size, cost, and reliability of the devices.
During the testing phase we broke two critical pieces of equipment with about a week to
go and were unable to meet our project deadline. For presentation purposes, we modified
our project goals and attempted to read data sent over the power lines with a homemade
decoder. Power line modems send data using FM modulation – just like the radio signal
– through the 120 V AC mains. A properly tuned receiver can decode the modulated
signal and send the data to the computer. At the time of writing, we designed and tested
the relevant components of the decoder but did not yet successfully receive a signal from
the mains. In sum, we learned some important lessons regarding the proper usage of
evaluation boards and like to think we could do better next time.