Another wee project to pass the time 
Most energy providers give away free ‘energy monitors’ to see how electricity you are using. They’re nice little wireless devices that calculate how much lecky you’re using at any time by attaching a wireless clampmeter to your positive feed into the lecky meter. I got mine from E-On where you just fill out a questionnaire and they send you it in the post.
E-On’s is a re-branded one of these:
Current Cost – Reducing your energy bills so you can live a greener life!
These guys seem to sell them the branded version for £40 (not bad for free from a 5 minute questionnaire!)
http://www.ecofreak.co.uk/products/0/24 … White.html
These units come with a USB connection for your PC. The software only works in Windows though, which for me was no use. That got me thinking – what if I plug it into a Linux box. Well, what happens is the device presents itself as a USB serial port (57600 baud, 8N1). This means you can interrogate the data stream very easily to see what the unit is sending. It turns out it sends an XML blob of sensor data every 6 seconds (makes calculations easy as that’s 10 a minute).
What use it this? For one you can compare what you are being charged by the meter with what this unit says (useful as you take the lowest value and argue your bill) and also it means you can graph the data over time. What I was thinking was rather than all that nonsense why not just make it display the data in a web page, with pretty gauges.
There are 2 stats I care about
1) Current usage in watts
2) Current temperature (just `cos)
The outcome is the attached screenshot, which updates every 6 seconds. It uses Google’s visualisation API.
The point of all this is to save ££! You can see what is using power in your house and turn things off when you’re not using them. It might sound all geeky and pointless but you’ll be surprised to see how much power random things use.
I’ve also attached the source code the gauges (energy.zip). If you’re running Ubuntu you need to install apache2, php5, libapache2-mod-php5 and libdate-manip-perl. Just extract the zip & tarball to /var/www/
You need to run this in a terminal to get it going:
chmod +x /var/www/energy/get_stats.pl
/var/www/energy/get_stats.pl &
Then in a web browser go to: [URL=”http://localhost/energy/”%5Dhttp://localhost/energy/[/URL]
