In part two I said I hadn’t done humidity yet. Now I have – it was fairly easy to do and I was short of something better to do in the wee hours of the morning.
Twelve hours:
One day:
I was asked in #bitfolk whether the station did anything other than temperature and I remembered that WSDL gave the dew point so thought I might as well add that too.
The maths required to calculate dew point and the background information is given in the Wikipedia article but for want of an excuse to use the LaTeX plugin for WordPress, the dew point 
is given by:
Where 
is given by
The bottom pair of lines in the temperature graphs in the last post show the dew point.
So nearly a week ago I got a weather station. Since then, I’ve hacked up some Python to deal with the temperature data and spew it into graphs. I haven’t got to doing the same with the humidity data, that can be Part Trois…
Anyway, graphs (update every 15 minutes). The last 24 hours:
The last week:
If anyone’s particularly interested I could post the Python that does this. It’s not the most exciting (or, I don’t doubt, the most well-written) code in the entire world but there’s probably someone weird enough to want to see how dire a job I can do of chopping a string up.
I added some optimisation to only parse lines which haven’t been seen before using a temp file so after the initial run the longest part is now uploading the images.
Apparently weather stations are a “conversation killer, if there ever was one!!!”. Who would have thought it?
I’ve wanted to set up/build a weather station for a while; lazyness and apathy were mostly what stopped me. Last week, I bit the bullet and bought an Oregon Scientific RMS300 (change from 35 quid from OS themselves).
It comes in two parts: a base station with a screen and built in temperature/humidity sensor and an included wireless sensor (by default labelled “outside” as a serving suggestion).
The supplied (via download) software, “OS Weather”, is…pretty shit. It doesn’t work on Windows 7 (“trial version” available “end of June”, apparently) and I couldn’t be bothered setting up a virtual machine to screw about with it.
Next up was Weather Station Data Logger. It’s good, but I have more than enough machines running 24/7 without adding a Windows one (and again don’t particularly want a Windows VM). I have machines which do run near-enough-24/7 but run Debian GNU/Linux so the ideal solution would run under that and ideally headless.
Enter the WMR100 module which will do all the work of getting the data out of the base station and its wireless sensors and present them in a fairly easy to manipulate format:
DATA[20100622001211]:type=TEMP,sensor=0,smile=0,trend=,temp=24.7,humidity=42,
dewpoint=0.0
Next magic trick will be to get the data I collected with WSDL and the data that’s being collected with WMR100, stick it all together in some way, and start getting it into graphs of some description. rrdtool‘s the obvious candidate.