Sunday, September 8 2019
This evening I assembled my first wheel-powered Raspberry-Pi-controlled rover using the remote-controlled truck with the four mechanically-linked wheels as the platform and an L298N board as the H-bridge (it can handle more power than the L293D I'd used in the Waterbot). The L298N even has a built-in 7805 power regulator that could theoretically a Raspberry Pi (though using a linear regulator would be inefficient). Everything was going great until I tried to fire up the Raspberry Pi. But every time I connected it to power, the regulator reset. Testing the wires, there were no apparent shorts between ground and 5 volts. After carefully looking at the the Raspberry Pi, I happened to notice a glob of solder bridging a bunch of pins on the HDMI connector. Had I somehow done this when soldering the pin header? It seemed unlikely, particularly given how solidly the solder was stuck to the pins. I couldn't simply pick it off as I hoped. To get rid of the glob, I was forced to remove the HDMI connector entirely (as well as some other tiny components nearby). But even with that gone, the board had the same problem with some sort of internal short. Ultimately I had to abandon it and grab another Raspberry Pi from my collection of small magical devices. I strongly suspect that the bad Raspberry Pi arrived here with that glob of solder on its pins. It had probably passed quality control and then been spattered with solder before being shipped. It's not the first time I've gotten bad stuff from Adafruit, but I love them anyway.
The new Raspberry Pi successfully powered the rover's motors, using a slightly-modified version of the software I'd written for the Waterbot, though not everything was working correctly. I could've stayed up late and gotten it working, but I had to get up early tomorrow for my day job.
The other day I discovered another band that I've been enjoying. It's a multi-subgenre metal group from Holland called Epica, and the song that drew me in is entitled "Design Your Universe." It's big and absurd, with a delightfully jarring combination of distorted guitars, double-kick drums, orchestra, two kinds of grunted vocals (including a grunted falsetto!) and an angelic lead singer accompanied by what sounds like a choir of angels. "Design Your Universe" is full of the kind of creepiness that would be impossible without a certain measure of beauty for the ugly to contrast with. Another great over-the-top pan-metallic song is "Kingdom of Heaven," which has some Middle Eastern pretenses. One of the interesting things about the band (at least as presented in the video for "Design Your Universe") is the fact that none of them appear to have any tattoos. It's jarring to see such terrifying music coming out of people with no evident body modification. But it's possible that not getting tattoos is one way for millennials (at least in Europe) to differentiate their appearance from that of their parents. I've also noticed such generational flip-flopping happening with regard to eyewear and facial hair.
Most of the books I'm discarding in my ongoing laboratory bookshelf reorg.
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