Making a coil to inductively sense current flowing through 2-conductor house wiring cables, without modifying the house wiring.

Making a coil to inductively sense current flowing through 2-conductor house wiring cables, without modifying the house wiring.

I used a Raspberry Pi and an ADS1115 A/D converter to sense the output from my coil and graphed it using ascii graphics on the Raspberry Pi computer. I also experimented with how much current it takes to instantly pop a breaker.

[Adam] shares his wash-bots with roommates, and they aren’t close enough to combine their lights and darks and turn it into a group activity. They needed an easy way to tell when the machines are done running, and whose stuff is even in there in the first place, so [Adam] built a laundry machine monitor that uses current sensing to detect when the machines are done running and sends a text to the appropriate person.

Each machine has a little Hall effect-sensing module that’s carefully zip-tied around its power cable. The signal from these three-wire boards goes high when the machine is running and low when it’s not. At the beginning of the load, the launderer simply presses their assigned button on the control box, and the ESP32 inside takes care of the rest.

https://hackaday.io/project/169990-easy-laundry-monitor

A team of researchers at MIT has developed a device designed to give home owners a better picture of how much power their individual appliances are eating up. The gadget, which was outlined in a paper published in a recent edition of the IEEE Sensors Journal, offers a simple installation process that involves securing it over a power line with a zip tie.

The stamp-size sensor self-calibrates and is capable of monitoring individual appliances courtesy of software developed by the team, even going so far as isolating time segments, like when a refrigerator goes into defrost mode. It also relies only minimally on cloud-based servers,

MIT estimates a commercial cost of between $25 and $30 for the sensor

What’s wasting power at home? Ask your app!
New system from MIT can identify how much power is being used by each device in a household.
http://news.mit.edu/2016/wasting-power-home-app-0801

If you want to save on your monthly electric bill and reduce your greenhouse gas emissions at the same time, you might buy a new, energy-efficient refrigerator. Or water heater. Or clothes dryer. But if you can only replace one of these, which will give you the biggest payback?

While many groups have worked on developing devices to monitor electricity use, the new MIT system has some key advantages over other approaches. First, it involves no complex installation: No wires need to be disconnected, and the placement of the postage-stamp-sized sensors over the incoming power line does not require any particular precision — the system is designed to be self-calibrating. Second, because it samples data very quickly, the sensors can pick up enough detailed information about spikes and patterns in the voltage and current that the system can, thanks to dedicated software, 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.

Own your own data

Perhaps most significantly, the system is designed so that all of the detailed information stays right inside the user’s own home, eliminating concerns about privacy that potential users may have when considering power-monitoring systems. The detailed analysis, including the potential for specialized analysis based on an individual user’s specific needs or interests, can be provided by customized apps that can be developed using the MIT team’s system.

Tests of the system have showed its potential to save energy and greenhouse emissions — and even to improve safety.

“For a long time, the premise has been that if we could get access to better information [about energy use], we would be able to create some significant savings,” Leeb says.

First was the ability to monitor changes in voltage and current without cutting the main incoming power line to a home or business (an expensive process requiring a licensed electrician) or plugging every appliance into a special monitoring device. Other groups have attempted to use wireless sensors to pick up the very faint magnetic and electric fields near a wire, but such systems have required a complex alignment process since the fields in some places can cancel each other out. The MIT team solved the problem by using an array of five sensors, each slightly offset from the others, and a calibration system that tracks the readings from each sensor and figures out which one is positioned to give the strongest signal.

every motor or device has distinctive characteristics as to exactly how fast and how much the voltage varies, or spikes, at the moment the device switches on, or as it operates.

Once the system is developed into a commercial product, Leeb says, it should cost only about $25 to $30 per home.

We’re trying to lower the barriers to installation,”

The new IMC-Hall current sensor MLX91205 is a single axis integrated magnetic sensor based on the Hall Effect. It produces an analog linear, ratio-metric output voltage proportional to the applied magnetic field parallel with the chip surface.

The circuit is fabricated using a standard CMOS process. The additional ferromagnetic layer (IMC-Hall = Integrated Magnetic Concentrator, Triaxis Technology) that is added in a simple post-processing step, amplifies the magnetic field and concentrates it on the Hall elements. Therefore, the circuit features very high magnetic sensitivity, low offset, and low noise.