It might not look like it, but that is a wondrous thing. It represents the next step in home hacking with the current cost meter. It is a lead which connects the current cost meter to the serial port on a lower power PC that runs a simple Perl script that records our power usage. The PC runs a script that captures the information from the current cost meter (current power used, in Watts, and temperature in ‘C) and build pretty graphs that are then published on a local web server.
Here are some of the useful resources I used to get it done:
- A post from jibble.org (now gone).
- Crouching Badger’s experiences with the USB version of the cable with links to a simple perl script.
The Jibble post got me started, although not being a PERL programmer or RRD user meant some of the “easy to make” changes weren’t actually that “easy to make”. Having learnt RRD a bit more, I’m impressed with it – great for performance monitoring of all sorts of thigns. It will take something more to move me to PERL as a programming language – PHP is as non-visual as I’m going to get. Some other pointers that helped (and give you an idea what it is all about):
- Dale Lane has done a fair bit – it was good to meet him at HomeCamp (I like Dale’s daily electricity bill too – I’ve build something similar, but taking the Kilowatt hours figure from the Current Cost Meter).
- Likewise Nicholas O’Leary has a series of posts.
- There is also a Google code repository.
- Ben Smithurst’s posts were also very helpful – a full script that updates rrd and an sqlite database too.
A slight warning: the commonly used PERL script fails when the temperature goes bellow 10’C though (since the current cost prints a leading space then, which causes the perl string matching clause to barf) – keep your current cost warm or fix up the script ;).
I have been amazed at the power of measuring usage in changing behaviours. Measuring really is the first step to managing. Even more excitingly, I have noticed that my gas meter is readable (via a magnetic or optical sensor) so I should be able to track that too soon – as if I’m not driving the family crazy already. Here’s a day of our electricity use (with min, max and average power):
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