A couple of weeks ago I came across a bunch of blogs written by IBM folk at Hursley Park, in which they described how they’d been playing with the CurrentCost energy monitor so they could get the data out and send it to twitter feeds, produce comparative graphs of consumption (like those above), and other stuff.
I’ve been interested in this idea ever since I saw Wattson by DIY Kyoto being demonstrated at DesignersBlock a couple of years ago… the CurrentCost is pretty fugly compared to wattson, but then again it’s far cheaper. I just bought one for £28 from eco gadget shop.
The system comprises a clamp that you fit in your meter cupboard, which then measures the amount of electricity you’re using and transmits it via radio link to a small visual display that you can use to keep an eye on things.
There are other devices that do similar things, but the CurrentCost has a serial port through which it outputs its readings every 6 seconds or so, which means you can use the data for whatever you like. It’s even in XML.
The only downside is the connection — an undocumented RJ45 jack. There will eventually be a data cable available, but it looks like only IBM people have this at the moment. I spent some time today trying to fathom out the connection but the pinout doesn’t appear to match any of the conventions for RS232 over RJ45. I chopped up an ethernet cable since they use RJ45 connectors and I have loads.
Anyway after some experimentation and thanks to Roo Reynolds I now have the unit connected to my Mac. It turns out that the data cable has a converter chip in it, and that the signals are 3.3V. I already have a cable that does the same (made by FTDI up the road in Glasgow, and which I recently bought from Adafruit in NYC — oops), so I used that to make the connection and all was well.
My unit sends its data at a particularly underwhelming 2400 baud, but since the packet only arrives every 6 seconds or so it’s fast enough. (Just!)
The pic’s a bit fuzzy, so here’s the order of wires from the ethernet cable, Left to Right:
green/white (pin 7, data in to CurrentCost)
blue (pin 4, ground)
brown (pin 8, data out from CurrentCost)
I’m looking forward to connecting this up to an arduino. I have a couple of different ethernet shields to try it with: the adafruit one with an Xport that I’ve had for ages, plus the new supercheap one from nuelectronics (£12.99! they also sell freeduinos for the same price).
Right, easily enough gobbledygook for one posting.