The current application of Flukso lies in the monitoring of electricity consumption and photovoltaic production. From the very start though, there has always been the desire to monitor all household flows (hence the Flukso name). Monitoring electricity just seemed more straightforward and definitely less intrusive than monitoring resources like water or heating.

That is, until one of our 'Fluksonians' (thanks Michel!) pointed me to Lieven's water and gas meter hacking experiments at lika.be. Lieven uses a Hall-effect switch which can either be inserted in the water meter's drilling or glued to the gas meter. When such a Hall-effect sensor is located close enough to the meter's rotating magnet, a clean pulse can be derived from the sensor. This allows the sensor to be coupled to a modified Fluksometer, with an extra output for powering the sensor. This is why you find two cables connecting the Hall sensor to the Fluksometer in the picture below.

Water metering with a hall switch

This means we now have experimental support for water metering. Yay! Well, at least for a certain popular type of water meter in Belgium. I am interested in finding out whether this approach works with other types of water meters as well. Post a comment or contact me directly if you're interested in tinkering with your own water meter.

Again, kudos to Lieven for devising this elegant water and gas measurement hack! It allows us to re-purpose the utility meter to our own needs in a non-intrusive, non-seal-breaking and robust way. We might even not be voiding our warranty this time.

This past week we have been testing Git and Github as Flukso's version control system and repository respectively. Being very impressed by both (The import from an existing SVN repository into Github is a killer!), and getting more confident at using these tools all the while, we have decided to switch to Github for hosting the official Flukso code and hardware schematics/layout.

You can find the project here. Currently a master and develop(ment) branch exists. If you'd like to keep up to date with the most recent developments, there's an RSS feed that tracks the commit history. Should you wish to check out the code and poke around, then this is a good introductory Git book available online, written by one of the Github developers. Although I don't have any experience with the Github issue tracking system, I'd like to suggest we use Github for submitting bug reports as well.

Fork me!

I came across a post on Engadget today [1]. It mentions Intel experimenting with the detection of specific household appliances being switched on/off through the use of a single sensor plugged into a power socket. I had read about a taxonomy of load signatures being proposed, based on device-specific transient voltage-current trajectories in [2]. Being able to single out individual appliances and switches from a single sensor sounds like the holy grail of domestic energy monitoring. Flukso data streams could be annotated with specific events (dishwasher turned on, hot water circulation pump running, …) by the use of just a single additional sensor. No need to start installing a plethora of wireless sensor nodes all around the house.

Some further Googling led to the excellent paper in [3]. It discusses similar research conducted at Georgia Tech. The researches detect the transient voltage pulses being generated on the power lines in the 100Hz-100kHz spectrum by a device being switched on/off. FFT transformation allows these pulses to be characterized by the system as vectors containing their spectral information. A Support Vector Machine technique is used for classification of newly detected pulses. The SVM does require initial training in order to successfully classify future pulses. The paper mentions a 90% success rate. Similar research from the Ubicomp Lab at the University of Washington is discussed in [4] and [5]. This time microphones or a single pressure sensor are attached to a home's water piping to detect the household's water usage patterns.

A very interesting read!

[1] Intel's experimental sensor analyzes appliance power consumption from single outlet
[2] A Taxonomy of Load Signatures for Single-Phase Electric Appliances
[3] At the Flick of a Switch: Detecting and Classifying Unique Electrical Events on the Residential Power Line
[4] Sensing from the Basement: A Feasibility Study of Unobtrusive and Low-Cost Home Activity Recognition
[5] HydroSense: Infrastructure-Mediated Single-Point Sensing of Whole-Home Water Activity

Update 18/04: Added a link to the Ubicomp Lab's project page.

All pending and future Fluksometer orders during our beta phase will be made with a 6-position screw terminal block. A single-phase Fluksometer will thus be able to read out two independent current clamps and one digital S0-type pulse output. A pulse output is present on most DIN-rail based kWh energy meters. If such an energy meter has a constant of 1000imp/kWh or 1 pulse per watthour, then it can be directly connected to the Fluksometer. The clamps need to connect to positions 1(+)/2(-) and 3(+)/4(-), the pulse output to positions 5(+)/6(-).

A three-phase Fluksometer with a 6-position connector will have its clamps connected in series. So clamp 1 will be on positions 1(+)/2(-), clamp 2 on 2(+)/3(-) and clamp 3 on 3(+)/4(-). Positions 5(+)/6(-) are again reserved for attaching a pulse output to the Fluksometer.

We currently only activate the 'main' input in the Flukso database. So either a single clamp (1-phase) or three clamps in series (3-phase). If you wish to experiment with additional inputs, let us know and we'll enable them in the database.

Note: This is not an April fools' joke!

Flukso announces the immediate availability of its JSON/REST API at the 2010 CeBit exhibition in Hannover. Fluksonians are now able to retrieve time series data of their electricity sensors through the Flukso API. Let's start with a working example:

curl -k -v -X GET -H "Accept: application/json" -H "X-Version: 1.0"
-H "X-Token: d8a8ab8893ea73f768b66b45234b5c3a"
"https://api.flukso.net/sensor/c1411c6b4f9910bbbab09f145f8533b9?interval=hour&unit=watt"

Where:

• X-Version: Denotes the desired API version. Should be set to 1.0.
• X-Token: A token associated with the specific sensor id. Different tokens per sensor will allow for varying access permissions, e.g. only allow data in 'month' resolution. This feature will become available in the near future. We now provision a single token per sensor. The token can be found next to its respective sensor id (see below).
• Sensor: Your sensor id's are displayed under the 'my account' -> 'sensor' tab. Just substitute the above sensor id and token with your own and you're ready to go.
• Interval: Should be one of {hour, day, month, year, night}
• Unit: Should be one of {watt, kwhperyear, eurperyear, audperyear}

Data is returned as an array of [unix timestamp, value] tuples, where value will be reported as a "nan" string when no data is available for the interval.

[[1267802160,69], [1267802220,69], [1267802280,73], ... , [1267805760,"nan"]]

The unix timestamp denotes the end of the interval for which the value is reported. So in the above example [1267802220,69] means that in the one-minute interval [1267802160, 1267802220] 69 watts of electricity has been consumed.

Thanks to Geert and Mathias for their valuable feedback during alpha testing.

Have fun!

Update 15/03/10: Added info on where to retrieve token information.