|
|
|
successfully multiplexed barometric sensors
Monday, March 16 2015
This afternoon I decided to do a proof-of-concept test of my multiplexed method of reading multiple barometric sensors with an Arduino. I'd done all the wiring for two sensors yesterday, so the only work necessary was in the software. There's already a library written to control the specific sensor I was using (I found the library at Sparkfun, where the sensor costs nearly ten times what you pay when you have it shipped on a slow boat from China.) All I had to do to the sample code was add a clause to twiddle the three pins that control which specific sensor the I2C bus connects to. Once that was done, I was delighted to see that the sample code was reading pressure from one sensor but not the other depending on which way I had the selector pins set. (To make the sensors show different pressures, I simply placed them inside my mouth and pressurized them to extent that my cheek muscles were able; I could increase their readings by about ten percent that way.)
Unfortunately, though, I was working fast, and I accidentally hooked up one of the sensor's connectors backwards, giving it +5v where it should have had ground and vice versa. My first indication that something was wrong was the smell. I reached down to touch the little sensor and it was a tiny frying pan. I immediately unhooked it, and, once hooked up correctly, it seemed to work (it still measured pressures). But it was never the same again. Now it tended to run hot all the time. Fortunately, though, it only had cost me $1.76.
But even before that, I noticed that the two sensors I was using were giving readings that differed by about 8%. I wondered if this was a consequence of the multiplexing or poor quality control at the manufacturer. I can still use devices with this flaw in my specific application, though it would be much nicer if they all agreed on the air pressure from the start.
This evening Gretchen hosted a second dinner party featuring leftovers from our party on Saturday. Eva & Sandor were again the guests of honor, and our only other guests were Erica & Justin, the friends from the big vegan family compound up near Palenville. Gretchen spent a good chunk of the afternoon handmaking a whole new batch of tortelloni, though I had little that I had to do, since the house was still clean after Saturday's party.
We spent most of the party in the living room in front of the fire, and Clarence was present for most of it. He's a very outgoing and charismatic cat, and he can make other cat people jealous of their tiresome and problematic felines. Erica & Justin, for example, have cats that aren't good about using their litterbox. And one of their dogs occasionally shits in their bed. Justin is a vet, and he thought Clarence was in amazing shape for a 12.5 year old. He also diagnosed a nascent yeast infection developing on Ramona's pudendum.
In other news, the only person at the party with an interest in the new Apple watch was Sandor, though it sounded like his main use for it would be as a pedometer.
Since our dinner was a proper sit-down affair, the dishwashing job afterwards was much larger than it had been after Saturday's finger-food extravaganza.
For linking purposes this article's URL is:
http://asecular.com/blog.php?150316 feedback
previous | next |
