Thursday, December 13 2012
Today was a sunny one, so I encouraged Gretchen to go take a "vacation" down in the greenhouse upstairs. She ended up taking a stack of books and crossword puzzles and hanging out down there for several hours. Though the dogs never go down there with me, it was an odd enough occurrence for Gretchen to be going there that they joined her. And of course once they were basking in the sun on that comfy futon, they were glad they had. After awhile they were panting from the heat and Gretchen had stripped down to her over the-shoulder boulder holders. I knew about that last one even before Gretchen told me because occasionally I'd look out the window to check in on how her "vacation" was going. It's a great place to hang out, but with all that south-facing glass, there is little privacy from people in the big house.
In the early afternoon at this time of year the sun starts to be blocked by trees, and at that point I usually have to make a fire in the woodstove. Sylvia the cat likes to hang out on the ottoman directly in front of the stove, and typically she's already there before I actually start the fire. Later the dogs show up, and sometimes Gretchen will join them on the couch to read or whatever. This evening she was there and she expressed an unusual craving for this time of the day: coffee. Gretchen usually only drinks coffee on Sundays or while on vacation and generally prides herself for not having a caffeine addiction, but she's been liking it more of late. That she would be craving it so late in the day seemed to surprise her as much as it did me. She said she was mostly interested in the flavor and that ideally we'd have decaf to satisfy such cravings. But, perhaps because we're unrealistically clinging to our youth, we don't stock decaf in our house. So I ended up making a full french press of the real thing. We drank it as if it were a Sunday morning, hanging out in front of the fire in the woodstove and talking. It felt good and unusually speedy, perhaps because our systems were unaccustomed to processing it at that time of day. Eventually Gretchen and I went our separate ways and undertook our separate crackhead projects. She stayed up late cleaning the kitchen and I did I undertook further experiments with my weather station (which I will detail below). And at around 1:00 in the morning I took a bath, and I didn't go to bed until about three. Knowing getting to sleep would be hard, I took an Ambien.
fun with an ineffectual 433 MHz receiver board
This evening I opened up the Meade TE923W-M weather station yet again, having remembered that its ineffectually-weak 433 MHz receiver unit was a small circuit board connected to the rest of the device via a small ribbon cable. With the device open, I saw that the receiver was only connected to the rest of the circuitry with three wires. Three wires greatly limited the possible functions those wires could be serving. One must have been positive power, another must have been ground, and the third must have been received data. Given how terribly the 433 MHz board was performing inside the weather station, it seemed best to just remove it and, instead of having a connection for an antenna on the outside of the weather station, have a three-conductor connection for a wireless receiver board to be mounted elsewhere, perhaps on the roof. It's possible that with a different receiver (perhaps one operating at a different frequency), I can actually pick up signals from transmitters placed in the places I want to put them.
The smallest possible connector for to provide three wires is a stereo audio jack. The most common size for those is 1/8 inch, and I have them on hand. Once I had the jack set up, I began testing it for voltages. Surprisingly, though, the voltages it registered were very low, too low to do anything useful. At first I thought the connections were bad, but they all tested fine. And then I realized something: the weather station only turns on the receiver board when it expects to be receiving a transmission. This realization explained a lot of the station's idiosyncrasies. It doesn't for example, start displaying data from the transmitters immediately. It first has to be placed into a scan mode to look for them, a mode that concludes after several minutes. What must be happening during that mode is that the receiver board is powered up continuously, listening for transmitters. Once it finds what can be found, it powers down the receiver and only powers it up for each regularly-scheduled broadcast from each transmitter. Indeed, once I put the weather station in scan mode, I quickly found the ground and positive voltage pins, meaning that, by the process of elimination, the remaining pin was for data. I found that, not only would the 433 MHz receiver board work just fine from the end of a stereo audio cable, but it even worked on one 18 feet long, meaning I could place the receiver board on the laboratory deck right next to all the major weather sensors, where it worked very reliably. Unfortunately, though, even with a perfect line-of-sight to the greenhouse (some seventy feet away), an antenna placed directly on the receiver board failed to register a transmitter sitting out on the greenhouse deck. Clearly there was something wrong with this particular receiver board. According to reviews on Amazon.com, a lot of other people have problems with the range of the Meade TE923W-M. (By contrast, the old Ambient Weather WS-1090 receiver continues to log data from its weather sensors even though I've put it away on a shelf 15 or 20 feet further from them than it had been, though it uses a transmission band somewhere near 915 MHz.)
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