Yup. Just a teaser for now. I recently got a couple new pi B+ cards, and have already had some seeduinos (the seedy version of the arduino uno - ~$3 each if you know where to buy them...). I got a DHT22 temperature/humidity sensor from adafruit, and thought I'd test the accuracy (not too shabby) and response time (glacial) so I can write some "real" code later. Wouldn't it be nice to know the temperature of your plumbing system before it freezes? It's an issue here, since it's in a building I don't use for much else and sometimes it gets cold here in the mountains. Later, I plan to write "real" code for all this and put it on my network, maybe even with early warning-prediction so I don't have to sweat running around heating things if it's not going to be a problem, but get some heads-up ahead of time if it is - for that I need time-constants vs temp diff and windspeed etc and so forth...I'll get that later, right now I'm just testing one of the sensors I want to use (they are cheap).
And for fun, I did all this on the pi itself - perl, gnuplot, the arduino IDE, you name it, all but this post, since right now the pi web browser would like to have a re-boot but I have it busy taking data overnight and streaming live video...it's kind of funny, both the pi and the nuc systems here are totally dominated by the display power draw unless you go to that really dinky/useless one for the pi. We'll have to see about that in the future, as otherwise, either works really well for "no" power, even by my parsimonious standards for that. Though I have to say, the nucs are so much faster than the pi, they'd be used for most of everything themselves that needed any speed. Luckily, this doesn't.
I'll post the code for it all tomorrow after this collection run is over - I plan to let it run overnight. It is, as Bill said, cold as a witches elbow out there, especially for this time of year. We normally have about one day of this, but normally it's in the middle of December. Looks like it's gonna be a cold one.
Here's a plot where I was taking data kinda fast (5 second intervals) and just testing the sensor itself. I went to 1 minute for the overnight run since it's so slow anyway. You can see where after letting it sit on my bed for awhile, I dropped it out the window. It's on one end of a 9 wire flat cable I happened to have some stock of, one wire is +5v, one is data (in the middle) and the rest are ground, and it's about 20' long with a 10k pullup - so these things don't mind a little cable run, cool.
Beer o clock now.
Like I said, more tomorrow, including the code etc. but for now here's the response time plot of the thing. It's pretty obvious where I walked it over to the window and tossed it out, then later brought it back in. Good old exponentials, more or less.
Some might wonder why i work like this. Well, I had a very interruption filled day, so I didn't have the energy to focus on the other stuff on the TODO list like finishing the MCA project or making a new grid, both of which require some mental prep and the right attitude going in...which I didn't have, which is why I have a long list - I just do whatever "is lighting up right now" from a long list, and things get done when they get done. Nice to have the freedom to do that.