====== House Energy Monitor ======

===== Hardware =====


This topic details a mini project using the [[http://www.eonenergy.com/At-Home/Products/Products-Electricity-And-Gas/Electricity-and-Gas/Energy-Saver.htm|EON Energy Monitor]]:

{{05072008.jpg?350}}

EON have being given them away "free" when you sign up to getting energy from them. It is infact a re-branded [[http://www.currentcost.co.uk| Current Cost]] Energy Monitor. 

I noticed that on the bottom was an RJ45 connector, after a bit of Googling, I found [[http://www.yellowpark.net/cdalby/index.php/2008/06/15/setting-up-my-current-cost-meter| this]] and [[http://flickr.com/photos/pixelfrenzy/2499443217/|this]]. 

So using Chris Hand's infomation, the interface on the RJ45 is:

   * orange/white
   * orange
   * green/white (pin 7, data in to CurrentCost)
   * blue (pin 4, ground)
   * blue/white
   * green
   * brown/white
   * brown (pin 8, data out from CurrentCost) 

The level is 3.3v TTL so cannot be connected directly to an RS232 port, however I don't have one of them free anyway, so I used a USB to TTL 3.3v [[http://www.ftdichip.com/Products/EvaluationKits/TTL-232R-3V3.htm|serial converter]] (also used by Chris Hand) from RS (part number 429-307). Current Cost do sell the cable for a good price, but what is the fun in that!!!

Using an old Ethernet cable for an RJ45, connecting the USB to serial convert to the RJ45 connector was easy:

{{05072008_003_.jpg?350}}


Just connect the pin 4 (blue) of the RJ45 to pin 1 (black) on the TTL-232R-3V3 and connect pin 8 (brown) of the RJ45 to pin 5 (yellow) on the TTL-232R-3V3. If I get time I will make a better cable, but for now this works. 


===== Software =====

When the hardware connected, I used Minicom to check that it was working. There are two version of currrentCost available, one that runs at 2400 baud, and one that runs at 9600. Mine was a 9600. 

The device spits out XML data every 6 seconds. You do not need to request data.

I wrote a simple c program to read the XML stream and convert into a CSV file that gnuplot can understand. 

The code can be found {{energymonitor.tar.gz|here}}

This application runs on my Linux server and reads and converts the XML stream into the CSV file, I also have a cgi script to convert the CSV file into a picture. 

   * {{powergraph.cgi.txt| Plotter Script }}

This is an example plot:

{{powergraph.cgi.png?350}}


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