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LCD Valentine
Monday, February 14 2011
Temperatures reached up into the mid-50s today, the highest temperatures this side of peak winter cold. And so today we had a serious episode of melting. It wasn't enough to clear the ice pack in our driveway or the glass-like surface of our trails, but the deep snow pack on the ground compressed and a lot of snow melted from the roof. Happily, it all ran off without backing up into the structure and entering the house. Evidently the roof's ice dams this year are not effective barriers to the downhill flow of water.
My existing solar controller is run by a single Atmega168-based Arduino running about a thousand lines of code written in C. That's a lot of code for the simplicity of its tasks, but that's because I've added a whole command-line interpreter allowing me to peak and poke into its EEPROM and set various parameters governing its behavior. There are also algorithms to turn off the circulator if the hydronic fluid doesn't appear to be flowing and to shunt hot hydronic fluid from the solar panels over to the slab should the hot water tank get overheated. While it's easy to investigate the controller's state via a serial link while at my computer up in the laboratory, what has been lacking has been an easy way to read the controller's state while standing next to it down in the basement. Lacking enough pins to hook up a digital display, I'd instead designed a more steampunk solution: an analog meter and a parade of LEDs. The LEDs flash on sequentially, and as they do so, each of four temperatures are "displayed" by positions on the dial of the analog meter (using one of the Arduino's digital-to-analog pulse-width-modulated outputs). That system was actually pretty effective at quickly communicating the state of the solar controller at any particular time.
But now that I have a slave Atmega8, I have an embarrassment of extra pins, enough to support a standard 16-pin HD44780 parallel LCD module. (I have two 20 by 4 character units just gathering dust.) So today I decided to add an LCD module to the slave Atmega8. Again, as with the other things on this project, this hardware expansion went about as well as it could have gone. I hooked it up (using four-bit mode, which requires only six wires), uploaded an Arduino sketch, and I successfully displayed "Hello World!" the very first time. I soon changed the message to "Happy Valentine's Day Gretchen!" and moved the whole solar controller (with 9 volt power supply) to the island in the kitchen, beside the leftover Indian food. While it was still detached from the household heating system, I could use it as a digital Valentine for Gretchen to find on this, the tenth anniversary of the most important email she ever sent me, the one that ended 12 years of silence.
This evening Gretchen and I went over to Ray and Nancy's house for this week's airing of the Bachelor, which is only fun to watch when you're drinking a beer and hanging out with a group of suitably-cynical friends (as Nancy puts it, it's like watching Us Magazine). Deborah was also there, and having such mirth at the expense of those faking romance seemed like a particularly-apt thing to do when in the company of someone who didn't happen to have a significant other on this most romantic of days.
But before we watched the show, we sat around snacking, drinking, and joking with each other. We kept having the kind of absurd conversations that would have deeply perplexed anyone arriving on them late. This was something Gretchen noted on two different occasions. One of these was after I said, "Yeah, I keep a cheese grater in the kitchen because occasionally I like to have anal sex." How did such a formulation come to be? We'd been talking about "law fossils" in the legal system, that is, laws that are no longer enforced but are still on the books (and could be used against someone unlucky enough to be caught violating them while pissing off an authority figure). I imagined one of these laws as outlawing anal sex, except (for some reason) in kitchens. And then I imagined kitchens as being defined as rooms containing one or more items of kitchen equipment.
pictures from a few days ago
Clarence decided to get on top of Eleanor and she didn't care.
Seriously.
Nigel.
pictures from today
The existing Arduino-based solar controller (with Arduino removed). I took this picture so I wouldn't have to keep going downstairs to research how it was wired.
A huge snow pile dug from the driveway where our main garden normally is. The dark spot is where I've been dumping my coffee. As the thaw began today, I thought I should photodocument the snow before it all vanished.
Our icy parking area.
Snow on the roof and all that has fallen off of it.
Our ice-glazed driveway.
For linking purposes this article's URL is:
http://asecular.com/blog.php?110214 feedback
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