JokamajoInstituut

The 8-pin terminal blocks arrived early this week. We've now mounted our sensor board onto the router board and connected the 4 sensor ports to the terminal block.

Flukso sensor node internals

Since our first prototype implementation based on an Arduino and Fonera 2200 hybrid late last year, we've been busy designing an integrated sensor board for Flukso, our community metering application. The board has an ATmega168v microcontroller (uC) at its core and contains sensor debouncing and signal conditioning circuitry. We can connect one analog and up to three digital pulse sensors to the PCB. Power (3.3V) is drawn from the 4-pin UART header of the main router board.

Flukso sensor board

Last Saturday I attended the second edition of Homecamp at Bash Creations in London. You can find the Flukso slides I presented on community metering here. All in all, it was an interesting day, packed with presentations and loads of conversations on home monitoring and automation, drained in a big sauce of sustainability. Despite being an unconference, you still need a group of people pulling it all together. So a big thank you to Chris Dalby of Yellowpark, James Governor of Redmonk and anyone else who helped in organising this second Homecamp!

At Jokamajo we're currently alpha testing a social metering application called Flukso. Flukso lets you compare your total electricity consumption to that of other households. These can be family, friends, colleagues, you name it. With Flukso, we're trying to turn those abstract watts and kWh's into something more tangible. You can display time-series charts covering the most recent hour, day, month or year. You can also dynamically add or remove other Fluksonians' (yeah, by signing up to the trial you're also getting a new passport) data onto the chart. If you're interested, you can check it out here. Note: Due to privacy reasons, we're only showing my personal chart.

fonduinoIn order to get this working, we needed to be able to transfer the pulses sent out by the energy meter to our Flukso server. We spent quite some time searching for a set of suitable off-the-shelf building blocks. We tackled this problem from two angles. Solving the networking problem first led us fairly quickly to a wireless residential router running a Linux kernel. OpenWRT is a good candidate as it lets us add all the software packages we need for our metering, like NTP support for timekeeping. As a fair amount of people are now using wifi to connect to the Internet from any room in their home, using a wifi capable router makes sense. Trying to detect the pulses sent out by the energy meter meant that we then had to look for at least one free GPIO on the router board and getting the linux kernel to pass these triggers to our software residing on the board. We solved this by using the hotplugging deamon. The major drawback of this solution is that we haven't got a long-term solution to store the meter value on the router. Since storage is all flash-based, you can only write to it about 100.000 times. Households having an average electricity consumption of 70kWh per week and the energy meter sending out a pulse for every Wh you've consumed, means that you're burning through the flash in less than two weeks time. That's a bit short, even for an alpha trial...