millipedes for hummingbirds
Wednesday, June 17 2009
I am admittedly neurotic about some things. If something breaks, for example, I will spend an inordinate amount of time and effort trying to fix it. I don't like to give up on material objects, even after they suffer Humpty Dumpty style fates. Today I happened to notice that Gretchen had, with a vacuum cleaner, accidentally run over one of my dual-sensor digital thermometers, which had been in her library quietly measuring and forgetting temperatures since I installed a hydronic zone there back in March and wanted to see how it affected temperature. Gretchen had actually run over the sensor wire, which the rotating brushes had cut into several segments. This wasn't a big deal; all I needed to do was find the sensor and then I could make the thermometer whole again. So I dumped the vacuum cleaner bag in the western edge of yard where I normally dump it; the dust bunnies, ash, coffee grounds, skin flakes, sawdust, pollen, and drywall powder quickly unites with the turf. And I look through it. I found little gold stars and crescents, paper from a hole punch, a guitar pick, a penny, and another segment of the thermometer cord. But the sensor wasn't there. I checked the vacuum cleaner again and the floor of the library several times, but found nothing.
So then I thought maybe I could just replace the sensor, which is a thermistor, an electrical resistor whose resistance changes with temperature. The problem with this idea, though, is that the world is full of many kinds of thermistors, and, perhaps more troubling, the nomenclature describing them is imprecise. A thermistor is typically described using a single resistance (say, 10 KΩ), but what does that mean? Does that mean it can never register a greater resistance than 10 KΩ or does that mean the middle of its range is 10 KΩ, and if so, what temperature does that happen at? I went to Mouser Electronics at looked at the datasheets for the many thermistors they sell and was soo lost in confusion, mostly because manufacturers publish single data sheets for many of their products which are then distinguished only by a few digits in a very long product number. None of these featured the thing I was looking for, a graph showing the (hopefully linear) relationship between temperature and resistance, the only information that mattered to me.
I soon gave up on commercial thermistors and turned my attention to the thermistors I have on hand. It turns out that I had quite a few, ranging from a pouch of "100 KΩ" glass thermistors, some of which I'd used in my solar controller project(s), to sensors made for other digital thermometers. I also had what looked like thermistors on some old scrap computer motherboards, which I know come equipped with temperature sensors. Removing one such device from the hollow inside of a Pentium IV socket, I found it provided about 20 KΩ at room temperature, and though it varied nicely with temperature, wasn't an accurate replacement for the missing thermistor. The thermistor I needed had to demonstrate about 9 KΩ at room temperature (this is what the thermometer's still-intact on-board thermistor was registering).
It had been an interesting rabbit hole to go down, but I had to regard it as entirely educational. A replacement thermometer costs only about $10, and the one with the amputated sensor still works for three of its four functions.
This has been an unusually rainy spring and, in terms of biology, it's been remarkable for a few other reasons. There have been explosions in the populations of two kinds of invertebrates (slugs and large millipedes) and a crash in the population of hummingbirds. It's become almost impossible to walk barefoot to the greenhouse without stepping on at least one slug, and sometimes when I do so they explode with a loud cracking sound. More troublesome is their slime, which, though resembling mucous, is nearly impossible to wash away.
Regarding millipedes, in past years I remember them being rare, but now they're everywhere, their sleek brown (with subtle red accents) forms trucking across stones and asphalt like miniature passenger trains. I sometimes pick them up and throw them into the grass when I fear I might step on them, and when I touch them they react by curling into a flat coil. Unlike similar-looking millipedes in South Africa, these do not release cyanide gas.
As for the hummingbirds, they started out strong in late April but then mysteriously vanished. I almost never see them, and (more telling) I never have to refill their feeder. In past summers I'd have to refill the container almost every day in peak hummingbird season.
This evening I joined Gretchen to watch part of the Tim Burton version of Charlie and the Chocolate Factory. I'd enjoyed the 1971 version, partly for the casualness with which obnoxious children were dispatched but also for the goofy musical stylings of the Oompa Loompas. In this version, Johnny Depp affects a perfect Willie Wanka, a quirky gentleman who wryly stands back to let bothersome people destroy themselves with their own bothersomeness. Something about the strange way Depp pronounces vowells contributed to the zany mystique. As for the Oompa Loompas, the choreography and songwriting was kicked up a couple orders of magnitude, and we were treated to hallucinogenic multimedia interludes featuring a wide variety of musical stylings ranging grom R&B to Devo-bizarre, to Queenlike heavy metal). Interestingly, all of the Oompa Loompas have the face of one particular actor (Deep Roy), who must have been multiplied (and shrunk) using software.
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