Monitoring power

Tuesday, November 26th, 2013 at 9:18 pm

While some people are heavily against smart meters, I am not concerned. In fact when I received the initial notification about the installation my first thought was about the possibility of playing with new technology.

When they finally installed the meter it coincided with a co-worker getting solar panels installed which led to a number of conversations about ways to monitor power generation and consumption. Based upon previous research I had done I knew that other people in Melbourne had had success with Rainforest Automation devices which use the ZigBee Smart Energy wireless protocol to connect to the smart meter.

My co-worker opted for the EAGLE as his solar panels also connected over ethernet, while I opted for the (cheaper) RAVEn which is a USB dongle.

Once the devices arrived I had to wait a few more days until my smart meter was completely setup, but then it was a simple matter of entering the address and install code from the RAVEn into the online portal for the smart meter. After a quick test with the windows app, I plugged it into my Linux box to see it come up as a serial port.

It was nice to simply run cat /dev/ttyUSB1 and see it output an XML fragment reporting the instantaneous demand every few seconds.

The documentation for the XML API showed me how to send commands and how to convert the hex values to decimal and how to apply the multiplier and divisor. It didn’t take long to wrap this in a script to be called by MRTG:

Events visible in this sample include:

  • Hot water turning on at 11PM AEST and topping up a couple of times
  • Fan and light while getting ready for work
  • Fridge cycling on during the day
  • Use of oven to cook dinner
  • Lights and other usage when I am at home

Due to complications with having off-peak electric hot water (aka a ‘controlled load’) I do not get summation values, instead that is just a graph of the instantaneous load. So while it doesn’t give true usage, it is a good enough indicator.

Currently this graph is available to anyone who knows the URL, and while it can let someone determine when I am or am not at home, the easier way to do that would be to go into my backyard and look through a window.

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