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MIT Invented A Single Sensor To Monitor The Power Used By Every Gadget In Your Home

Forget annoying smart appliances and an app for every gadget. Monitor all your home energy use in unprecedented detail.

MIT Invented A Single Sensor To Monitor The Power Used By Every Gadget In Your Home

[Photo: Iasha via Shutterstock]

Perhaps you want to monitor the gadgets and appliances in your home, but you don’t want to buy a ton of extra gadgets to do it. That’s a shame, because knowing how much electricity you’re burning is the first step to cutting back, saving not just money, but also saving the planet.

If you’re a lazy, cheapskate environmentalist like the one described above, then we have good news, in the form of an experimental MIT dongle that you attach to the main power line into your home. Once attached, it can monitor the consumption of individual devices all over the house. Clever, right?

The device is called a "non-contact electromagnetic field sensor," and it's designed to be easy to use. You stick the little sensor over the incoming power line, and it senses the electricity running through it. The clever part is in the combination of the fast sampling rate, which is accurate enough to detect power spikes and patterns in voltage and current, and the software, which can "tell the difference between every different kind of light, motor, and other device in the home and show exactly which ones go on and off, at what times." according to a story posted on the MIT News website.

Bryce Vickmark

The sensor is actually an array of five sensors, all offset so that their readings are coming from different directions. The differences between these reading are used to determine which sensor is getting the strongest reading. From then on, the wireless sensors feed their raw data into software. This has been tuned to detect the signature spikes of various kinds of gadget and appliance when they are switched on and off, and the rate and size of the current and voltage they use. By testing the system in real homes and other situations, the team has built up a database of these signatures.

The result is a system that can give the user highly detailed info about their current electricity usage, as well as letting them zoom in on spikes in the past to see what caused them. The software is sensitive enough to spot when a refrigerator goes into a defrost cycle, for instance.

In testing, the sensor proved its worth immediately. In one live test, installed at a military base, the sensor ratted out a section of the camp where large tents were being heated all day long, even though they were empty. Another trial revealed that poor wiring had left water pipes in a home carrying live voltage.

The detail of the system is its big selling point, but also its potential downside—what happens to all the data that it is gathering about your power-usage habits? The answer is, thanks to a cautiously designed system, is "not much." Instead of sending the raw data off to some cloud server to be processed, the bulk of the data is kept in your home. Only a small amount is sent to the cloud, which means that the private stats never leave your home. These privacy issues probably won’t concern most homeowners, but are important nonetheless. And the privacy guarantee will also make the technology more attractive to big businesses, or even the military, as seen in the previous example.

But the real key is that the whole system is so simple and easy to install and use. Once the sensor makes it into stores, it should cost $30 or less, and doesn’t even need an electrician to install it. "It just goes on with a zip tie," John Donnal, co-author of the paper describing the device, told MIT News.

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