#qi-hardware IRC log for Sunday, 2014-07-06

whitequarkI added a probe to my CNC mill and it leaks steps like the russian pump leaks water09:27
whitequarksomething needs to be done with this, it's terrible. .1mm of displacement over 10mm Z move is typical09:27
eintopfwhitequark: do you live in moscow?10:07
whitequarkeintopf: ^10:47
whitequarknot really12:09
whitequarkhm, according to http://www.cnczone.com/forums/chinese-machines/190286-yoocnc-3020z-d52-losing-steps.html, the problem with lost steps is very well known and caused by missing caps on TB6560 drivers12:10
eintopfwhy isn't cool?12:17
eintopfoh the government etc...12:18
eintopfand you need a gun to drive cars, I saw some russian dash cams videos12:18
eintopfsorry, I know russian from tv and internet only12:19
whitequarkit's just a very poorly planned city that's pretty shitty to live in regardless of anything else12:22
whitequarkand expensive12:22
kyak..and yet it attracts people like holy grale...12:46
eintopfI heard there are some devices for free12:47
eintopfwindows, x86...12:47
whitequarkkyak: well, if the other places are even worse...12:49
eintopfwhitequark: how do use internet in russian, with tor or anything else?12:50
eintopfI mean it's "free" there?12:50
whitequarkalthough smaller ISPs don't have DPI hardware12:50
whitequarkso for example mine ignores the censorship rules12:50
eintopfah, ok12:51
whitequarkanyway, even if it didn't, I do everything via OpenVPN to UK12:51
whitequarkthere's a saying, "the strictness of russian laws is compensated by optionality of conformance"12:51
whitequarkthe censorship thing is an incredibly typical example12:51
whitequarkanyway. a law recently passed that would make storing *any* personal data outside RU illegal since 201612:52
eintopfI didn't heard about this12:53
whitequarkobviously, it is absurd12:53
eintopfbut you don't want trouble with the russian police12:55
eintopfif you store personal data on other servers12:56
eintopfor it's only for government12:57
Action: whitequark shrugs12:57
whitequarkno one actually cares about personal data, it is a law written for selective enforcement12:57
whitequarkbecause, well, in the age of internet, personal data of literally anyone will be stored overseas somehow12:58
eintopfmy old mathematics professor cames from russian.12:59
eintopfShe didn't know that calculators can calculate determinate from matrix...12:59
eintopfshe never used one. :D12:59
eintopfafter she knows that, it was forbidden to used calculators in exam13:00
eintopfokay maybe she used one but ten years ago...13:01
whitequarkum, sure13:02
whitequarkthere's no point in using calculators on exams13:02
whitequarkif you need one, you screwed up somewhere13:02
eintopfin digital logic exam, we could use a ~300 page script13:03
eintopfbut I need only one page13:04
eintopfsummarize of flip flops13:04
eintopfokay, maybe you wouldn't need any page for this exam13:05
eintopfwas easy13:05
kyakthat's normal, calculators (even non-programmable) are not allowed during high-school final exams in maths13:16
kyakyou can use a ruler and reference books13:17
kyakat least it raises confidence that future politicians/whatever won't get stumped by "how much is 7 by 8?" question13:18
kyakyou can guess i'm talking about this episode: http://www.buzzfeed.com/jimwaterson/watch-george-osborne-refuse-to-answer-a-7x8-times-table-ques13:20
Action: dos1 doesn't know how much is 7 by 8 without counting on fingers13:35
dos1but when it takes me about 2-3 seconds, then I can't bother ;)13:36
whitequarkI can add and multiply 3-digit numbers in my head, it's convenient when, say, you have a drawing with relative offsets and you need to go to absolute13:41
whitequarkor when you need to know how much, if approximately, something in bulk will cost13:42
whitequarka skill I use daily. so I say, fuck calculators, too much hassle13:42
dos1adding and substracting large numbers in head is easy; multiplication is a bit harder; for some factors like 7*8 I need some quick help with fingers, but once result is already in short term memory it's no big deal; but with both factors being 3-digit I'd have problem to do it entirely in head13:50
dos1but if only there's some piece of paper available (like on exam), there's absolutely no need for calculator...13:50
whitequarkyeh paper too13:51
dos1but by chance 7*8 isn't yet ;)16:37
DocScrutinizer05I also don't know 7*8, but I know 8*7 ;-D16:38
dos1my mind seem to not like sevens for some reason16:38
DocScrutinizer057 is an ugly number16:38
DocScrutinizer057, 14, 21, 28, 35, 42(!), 49 (eeew), 5616:39
DocScrutinizer05and then even 6316:40
DocScrutinizer057*7 is a nasty one you need to know16:43
DocScrutinizer05whitequark: nice one about abysmal chinese EE done for your CNC16:49
Action: DocScrutinizer05 ponders getting a scope finally16:49
DocScrutinizer05for sure I'll want one with complete control/data over USB as an option16:50
DocScrutinizer05plus I'd instantly plumb together a 8 channel mux based on reed relays for that16:53
DocScrutinizer05dunno if contact/A/B reed swaitches are available in ultra-tiny. Hope so16:55
DocScrutinizer05you don't what to build such mux in a way where in theory two contacts could stay closed concurrently and would short two inputs then16:55
DocScrutinizer05http://wstaw.org/m/2014/07/06/plasma-desktopkm1814.png is what you wanna do17:02
apeleteHi larsc17:15
DocScrutinizer05and use relays sth like http://www.futureelectronics.com/en/technologies/electromechanical/relays/reed-relays-switches/Pages/6362230-W172DIP-3.aspx?IM=017:16
apeletedon't know if you sent this patch upstream already:17:16
apeletebut if you haven't yet, could you merge the change from this one it too ?17:16
apelete 17:16
apeleteeither merge the change in one patch or pick them both, as you wish17:17
apeletewould be nice to have the full fix upstream either way :)17:18
whitequarkDocScrutinizer05: re abysmal EE, yes, indeed!17:32
whitequarkI don't think they *either* read the DS *or* actually tested the values they claim17:32
whitequarkWTF, how do you even sell such shite17:32
whitequarkI wonder if they turned it on at all!17:33
DocScrutinizer05(relay) http://www.serelays.com/library/magnecraft-catalogs/8501CT1001.pdf p15 figure Q SPDT with diode17:34
DocScrutinizer05whitequark: remember audio of GTA02?17:35
DocScrutinizer05from schematics I calculated that with nominal 16R headphones, you got a HPF with a -3dB cutoff freq of ~400Hz iirc. That device passed QA (before my time) since "it worked"17:36
DocScrutinizer05that's how chinese "QA" works17:37
DocScrutinizer05"oh yeah, some noise coming out" -- QA-tester puts checkmark to '[ ]Audio'17:38
whitequarkI mean, I can understand a single device17:38
whitequarkbut the whole design?!17:39
DocScrutinizer05they test with maybe a 800Hz sine wave or whatever, and it sounds beautiful via headphones17:39
DocScrutinizer05even looks good on scope17:39
DocScrutinizer05probably nobody of EE ever really used the device to listen to music17:40
DocScrutinizer05and even when they did, they probably wouldn't have noticed the missing bass17:40
DocScrutinizer05odds however are they tested the audio output for doing voicecalls, and there a HPF with a cutoff of ~400Hz is even _improving_ the legibility of the voice ;-P17:42
DocScrutinizer05to me it seems that chinese EE ofthe simply connect signals of same name together, no matter what17:44
DocScrutinizer05reading datasheets isn't a commonly appreciated discipline17:44
DocScrutinizer05pulsewidth, slewrate, noisefloor, dutycycle? forget about it17:45
PetrarcaCan I do that in order to create a +1 usb hub?    http://picpaste.com/simple-hub-cjhmowew.jpg18:37
whitequarkPetrarca: no18:53
whitequarkthis will violate USB protocol.18:53
Petrarcahow so?18:54
whitequarkwell, to begin with, the physical level requires a certain line impedance18:57
whitequarkand your T-connection has it completely wrong18:57
PetrarcaI see... but is it just a matter of wiring or do I need some specific IC to create a hub?18:59
Petrarcadamn it.19:01
Petrarcatks bro19:01
whitequarkhahaha I love the note in the stepper driver DS19:29
whitequarkIn addition, do not use any device that is applied the current with inserting in the wrong orientation19:29
whitequarkor incorrectly even just one time.19:29
whitequarkI can just see someone complaining "but I plugged it backwards *just once*! surely it should still work!"19:29

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