#qi-hardware IRC log for Saturday, 2014-06-14

nicksydneywpwrak: yup.....seen them before it's old :)00:57
nicksydneybut i like their form factor ...tiny weeny ;)00:57
nicksydneythey also have for AV https://store.gumstix.com/index.php/products/585/00:58
whitequarklol wtf. somehow I have a few leds on the slave side of this optocoupler, and they light up, despite there being no power source except the LPT port at the master side12:20
whitequarkGNDIO/VCCIO are connected to an isolating DC-DC converter connected to the slave side power supply12:21
whitequarkand no, no capacitors are involved12:22
whitequarkcan it be that uh... the photoelectric effect generates about 5mA of current inside an optocoupler?12:23
whitequarkthat sounds slightly absurd12:24
whitequarkalso the spurious voltage is 1.8V whereas the band gap in silicon is 1.2V so it's probably not that12:25
ysionneau14:21 < whitequark> http://localhost:4000/images/3020t/lpt-input.png < will be hard for us to browse this page :)12:57
wpwrakjut smake sure JP1.2 is high enough :)14:38
wpwrakah wait14:38
wpwrakif your bird did things correctly, ground floats, right ? :)14:39
whitequarkthat's not my PCB, that's the vendor-provided one14:41
wpwrakso ground floats14:42
wpwrakwell, or at least you don'thavegalvanic separation14:43
whitequarkI think it should float, yes14:43
whitequarkit should be galvanically separated14:43
whitequarkI mean, otherwise, what is the point of having the optocouplers there?14:43
wpwrakcargo cult ? :)14:43
rohwhitequark: optocouplers combined with schmitt-triggers are used for spike surpression and overvoltage protection in cnc/automatisation devices16:54
rohso they are not only galvanic separation ;)16:55
whitequarkhmm, makes sense17:22
whitequarkfun effect18:13
larscif you pump enough energy into it almost everything will become a light source ;)18:22
whitequarkwell, here, it's a semiconductor effect18:22
whitequarkdespite how it looks18:22
--- Sun Jun 15 201400:00

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