local Storage?


since i`m new here, let me first introduce myself a little bit:

i´m a computing/linux enthusiast from cologne/germany with some affinity to electrical engineering, energy and environmental protection, too - so it looks that flukso is just the project i was always waiting for :) . i have just come across this site via wikipedia article about home energy monitors.

i have spent some time with with currentcost envi , with good results. i like the envi very much. see http://umweltsuen.de/envi-demo-static/ for my home-power graphs.

what i´m absolutely curious about: energy monitors like currentcost, owl, efergy, wattson, flukso .... are mostly unknown in germany and there is no market yet, whereas in UK already 1 million ENVIs have been sold. i have asked some suppliers of green energy if they thought about selling energy monitors or giving away for free, like in UK, but they all gave negative response. looks like a conspiracy to me... :)

currently, i`m searching for a way to have long-term & detailed logging capability without need of running a home-server or flat-rate internet connectivity. for example, i would like to put an envi in my parent`s home to be be queried via PC from time to time to show those nice graphs like those i`m currently logging via my home server.

i have set sort of an hurdle for myself:
that system should all be as low-cost as possible, as i think everybody should have such a power monitor with detailed logging capability and that should go well below 100 Euro.

so far, i have these little projects:

- hooking my envi to my home-server and creating graphs with rrdtool (this is in production for ~1 months now and works very well)

- adding openwrt kamikaze to netgear router, reading currentcost envi data and storing on usb-key, to be served via embedded webserver. basic tests look good. nice: you can hook the envi without usb2serial converter directly 1:1 to the board - just plain low-voltage ttl. problem: without internet connection, there is no timesource. so, running this standalone without rtc sucks, as you need to set the time with every power-loss.

- put linux on old compaq evo t20 thin client and run rootfs from usb-stick. have made some progress. what`s nice is that you can easily mod the t20 for having rtc working and you have 4 usb ports. problem: evo t20 still draws too much power, imho (~8W)

- creating a list of available home energy monitoring systems

so, having some device like fluksometer looks interesting and i`m curious if there is a way to run this without internet connection.
even if this will not be a planned feature, this is an interesting project. ( i also had a look at the fonera router for being a candidate to attach a currentcost to....)


icarus75's picture

Hi Roland,

Thanks for the introduction and welcome to the Flukso forum!

I can only second your remark about the widespread distribution of energy monitors in the UK. I attended the Homecamp unconference in London last year. I wrote a short post about the meeting on the Jokamajo blog. If I recall correctly, Martin of Current Cost stated that they had sold over half a million of their devices already. Imagine what this would mean if all of them were taking part in a mySmartGrid project.

Re the standalone option: If you could add an openwrt rrdtool package to the Fluksometer, you would be able to re-direct the readings directly to an on-board rrd. As for visualisation, you could add a page to the local LuCI web interface displaying charts similar to the ones on Flukso. I see two hurdles:

1/ How much flash and RAM does the rrdtool package require? We've got limited free space on the Fluksometer's 4MB flash, although squashfs might help us a bit.

2/ The limited number of write cycles to flash memory. We've already got some nice filtering/aging in place in the Flukso daemon. A solution might be to keep the measurements in ram and periodically write to flash e.g. once a day or when the web page is being displayed.


>1/ How much flash and RAM does the rrdtool package require?
not too much, but i think there are some dependencies. It fits well onto my netgear router, but iirc, that one has 8mb flash and 32mb ram.

>2/ The limited number of write cycles to flash memory. We've already got some nice
>filtering/aging in place in the Flukso daemon. A solution might be to keep the
>measurements in ram and periodically write to flash e.g. once a day or when the web
>page is being displayed.

yes, i already thought of storing the rrd`s in tmpfs and write them to flash once an hour or once a day....and including jffs2 that would probably not wear out the flash too soon. if there is power loss, we would not loose to much data and that would not hurt. furthermore, you could use external usb stick as storage for rrd`s. unfortunately, the fonera router is a little bit limited here - but if you want a more capable linux platform with more ram , more flash and usb, youre at least at twice the price like the fonera router....
still, the problem with no rtc remains. if you want to graph something over time, you need a timebase - and routers don`t have such as they can mostly get the time from the internet. no problem with an always on connection, but a problem at my parents home.

aboaboit's picture

You could always use a GPS receiver over BT, less than 50 EUR for both the receiver and the bluetooth dongle.

roland's picture

great links, thanks!

isn´t fonera 2.0g discontinued?

can`t find any source for buying and on fon site there is 2.0N which is much more (i.e. too) expensive

skynetbbs's picture

The fonera 2.0g is still for sale in Europe;
But from a recent interview they are going to launch a SIMPL device which will have usb possibilities as well (soldering usb port on it)...and a USB version later on...