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Posts uit oktober, 2013 weergeven

Diodes and (poly) fuses, week 41 (part 2)

I have today finally fixed the issues with my Raspberry-PI. If I have these issues everybody must be having them, USB problems! After spending the whole day measuring and tinkering it seems to work. There are some serious design-flaws with the board, to say the least. UPDATE: it is not completely fixed, after a few hundred open/close calls on a sound card (alsa on USB) the problem still happens, the USB locks up. I will not use a R-Pi again. What a piece of marketing hype it is.  One of the thing I need the R-Pi to do is run of 12 Volts, not a 5 volt USB connector. So I added a DC/DC converter (which also insulates the ground connection, which is always good when doing audio or mounting stuff in a car). It appeared to work fine but the usb-audio-card kept failing, after opening it 20 times or so. I also have a Pi-Face board connected so that complicated the situation. When it ran it ran OK, but sometimes it just did not work. I do not like these intermittent problems, so I

Diodes and (poly) fuses, week 41 (part 1)

This week has been a hacking week. I repaired an old charger for a small fork lift, and finally fixed instability of my Raspberry-PI board. First the battery charger, an old 30 Ampere 24 Volt charger for a small fork lift. After switching it on, the lights would light up, some clicks would follow (detecting the battery and voltage), and then a low hum (transformer overloading) followed by a flash of the fuse exploding (on the circuitboard in the charger). After some investigation I found out that the rectifier bridge was bad, just one diode had failed and was completely shorted out, I have no clue why this happened at that moment, maybe just a cosmic ray or a spike somewhere, nobody can tell. The diode was a BYD57-200 (that is a press-fit 200 Volt 35 Amp version). Going through the usual catalogs online (Farnell/RS/Reichelt/Conrad) it appeared that nobody was selling these anymore. I ended up buying one at Brigatti in Eindhoven (  ) it is a 30 minute