the day before the Adirondacks
Friday, August 9 2013
I have a couple Raspberry Pi boards that at some point I would like to incorporate into objects requiring their level of sophistication. They'd be ideal for "probelike" remote systems equipped with cameras, motorized mobility, sensors, and even robot arms. With the exception of cameras, all of that stuff interfaces to the Raspberry Pi through its GPIO port. I could rig together my own ribbon cable and make my own GPIO-based board from scratch, but I decided to save myself some trouble by ordering a RaspiRobot Board. It comes as a kit, and today I assembled that kit using my increasingly-crappy "best" soldering iron while overseeing the process with my increasingly-crappy short-range vision. (I already need bifocals.) Despite all that, the assembly seemed to go well and none of the possible short circuits I tested were actually shorted. So I tried firing it up. Nothing. Eventually it turned out that the onboard LM2940-5 (a linear power regulator similar to a 7805 but supposedly vastly-improved) had its output shorted to ground. The problem evidently had something to do with all the ground-shielding surrounding every pad of every type as though they were islands in an ocean. After cutting out that shielding from around the output terminal, I eventually got the LM2940 unshorted, but now it was putting out something like 6.8 volts, which is well above spec for something that needs to operate at TTL levels. Not knowing what to do, I replaced it with a 7805, which seemed to work okay, though it only took it a few minutes of driving the robot board along with the Raspberry Pi before it became scorchingly hot. Later I would read that the RaspiRobot Board's regulator is underengineered for driving itself and a Raspberry Pi. So on whatever I end up building, it will probably have to have its own discrete five volt power supply.
Meanwhile Gretchen had picked up her friend Eulayla from the bus station. Tomorrow Gretchen and I would be leaving with the dogs to spend another week on Lake Edwards in the Adirondacks near Gloversville, and Gretchen had arranged for Eulayla to come up from the city to stay in our house, look after the cats, and maybe work on a business proposal she's been procrastinating. Since Eulayla doesn't drive (she recently failed a driver's test), Nancy (who knows her from Brooklyn) had volunteered to provide transportation. This evening Gretchen, Eulayla, and I drove down to Nancy's place and picked her up and then we continued on to Momiji, the cheap & delicious Japanese restaurant in Stone Ridge, where we had dinner. We were joined briefly by David (the partner of Susan the artist; the two are renting a house nearby) so that he could pick up his apartment keys, loaned to us in case we wanted to stay in their Upper West Side apartment the other night. Dinner conversation touched on my fondness for trolling extreme right-wing Facebook pages, where, in response to such things as Nazi banners photoshopped onto the White House, I say things such as "#BENGHAZI is ten times worse than the Holocaust times that time in history when America underpaid the black servants it had imported from Africa."
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