Getting Started with the Current Cost Meter

My Current Cost meter has been running for just over two days. Apart from the microwave, oven and kettle it seems to be an accumulation of other items (such as leaving lights on, or the PC running) that racks up the cost. This probably sounds obvious, but seeing a monthly cost displayed with a pound sign in front of it helps to reinforce the point.

I wanted to understand what data was available from the unit, and compare it with the feed that Andy Stanford-Clark is producing on Twitter, to get me thinking about the possibilities.

  1. I downloaded the Java code written by Dale Lane and imported it into Eclipse.
  2. Dale’s code needs a class that is available in Trent Jarvi’s RXTX package; version 2.1.7 for Windows is installed by copying the rxtxcomm.jar into your Java Runtime’s \jre\lib\ext folder, and the rxtxSerial.dll to \jre\bin
  3. Windows wouldn’t install the the USB-serial converter for the USB cable but I found a link on getsatisfaction, also courtesy of Dale, to the Prolific drivers.

Now I can run the CurrentCostSample, which produces the following:

Stable Library
=========================================
Native lib Version = RXTX-2.1-7
Java lib Version = RXTX-2.1-7
27/11/2008 7:00 = 2.0
27/11/2008 13:00 = 2.8
27/11/2008 23:00 = 2.0
27/11/2008 21:00 = 1.8

etc.

The unit actually returns the data in XML format, which Rich Cumbers has helpfully detailed.

For some fairly short-term gratification I plan to plug the unit into my Linux box that is currently used for recording TV so that I can do more fine-grained / longer term data capture and think about publishing some useful events (perhaps over Googletalk initially). I expect there will be plenty of ideas at Homecamp tomorrow. In the spirit of power reduction I have also bought a NSLU2 network storage device
to run as a small server, which takes only about 4 Watts; not set up yet, but on the to do list.

If you are thinking of experimenting with the Current Cost unit, you might want to listen to Andy Stanford-Clark on the Tech Weekly or Automated Home podcasts. I also found Chris Dalby’s post pretty useful.

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