#qi-hardware IRC log for Monday, 2014-04-28

wpwrakDocScrutinizer05: i have a little "electronics vs. the human body" puzzle. let's assume you wanted to build a wrist watch like device whose principal function was to alert you of something, e.g., like an alarm clock.17:00
wpwraknow, the signal the device produces should be completely unnoticeable to others. so no buzzing or beeping, no flashing light, and also a vibration alarm may be a bit too intrusive17:02
larscI guess that rules out high voltage shocks as well17:03
wpwraki was thinking that one could perhaps use a mild electric shock, just across the wrist. do you think that would work well ? the shock should just be strong enough that one notices, not strong enough to cause involuntary muscle contraction or such17:03
DocScrutinizer05adjustable 100..10000V spikes. Possibly energy-defined, not voltage-defined17:04
wpwrakcan't that work with less ?17:04
DocScrutinizer05less than 100V are hardly noticeable17:04
wpwrak10 kV would arc ;-)17:04
DocScrutinizer05use a multiplier and adjust the frequency. It will nicely attenuate voltage with increasing load 17:06
DocScrutinizer05use sufficiently large electrodes17:06
wpwrakwhat would be the easiest way to produce such a 100 V charge ?17:06
DocScrutinizer05but not too large since that increases the power you need to apply17:06
DocScrutinizer05multiplier, as I said. Or boost converter17:07
DocScrutinizer05prolly both17:07
wpwrak(electrode size) well, the whole thing should be wrist watch sized17:07
DocScrutinizer05boost plus 4* multiplier17:07
wpwrakah, boost plus diode "ladder"17:07
DocScrutinizer05yeah, I *guess* 1..2 cm^2 per electrode (with one electrode as well could be much larger) should work17:08
DocScrutinizer05yes, ladder == multiplier17:08
DocScrutinizer05though ideally you use AC17:08
DocScrutinizer05less electrolytic wear of electrodes17:09
DocScrutinizer05but AC needs to be <500Hz to avoid skin effect17:09
wpwrakwear is probably not a big issue since it would have a very low duty cycle17:09
DocScrutinizer05try a boost converter with high voltage switch (GTA or sth)17:10
wpwrakGTA ?17:11
DocScrutinizer05don't forget OV-protection, so it doesn't fry your circuit when the clock has no 'load'17:11
wpwrakstill don't know what the acronym means :)17:11
whitequarkwhoa, c't hacks has arrived17:13
DocScrutinizer05dunno it they exist for e.g. 1A as well17:13
DocScrutinizer05commonly used in cut-off type dimmers17:14
DocScrutinizer05whitequark: incredible :-D17:14
wpwrakhmm, that looks like a big device. not ideal for a watch-like critter17:15
DocScrutinizer05there *are* smaller ones, with <350A17:15
DocScrutinizer05or use a IGBT, they also qualify for high voltage 17:16
wpwrakgtos don't seem to exist, according to digi-key :)17:20
whitequarkwhoa, the pictures and schematics sure motivate a great deal to read it17:22
wpwrakIGBT looks better :) but i guess the booster wouldn't really need to go that high anyway17:22
DocScrutinizer05it needs to go that high when you don't want to use multiplier17:23
wpwrakreading about electric fences ... "weed burners" hehe :) http://en.wikipedia.org/wiki/Electric_fence#Fence_energizers17:24
DocScrutinizer05V+ ->choke->(electrode)->(IGBT||350V-Zener)->GND-(electrode)17:24
wpwrakhmm ? why the IGBT between the electrodes ?17:26
DocScrutinizer05to charge energy into the choke17:30
DocScrutinizer05this design has a drawback of applying V+ to electrode1 all the time17:31
DocScrutinizer05of course you also can use a design like http://www.freepatentsonline.com/6801045-0-display.jpg and charge the capacitor via a multiplier17:32
DocScrutinizer05but you need a transformer choke then, of maybe 1:100 or sth17:32
wpwraknice, an explanation :)17:35
wpwrakah nice, even with regulatory backgrund17:38
wpwrakeww, complex17:39
wpwrakbut it looks as if most of this could just vanish into an MCU17:40
DocScrutinizer05the last one is actually pretty nice17:41
DocScrutinizer05and yes, you can replace IC2b and 7555 by GPIO17:43
wpwrakah. "car ignition" !17:43
DocScrutinizer05you need Q1, T1 and everything right of it17:43
wpwrakthere's a ton of circuits for THAT.17:43
DocScrutinizer05IC2a you need A/D input on MCU17:44
DocScrutinizer05sure there's a ton of circuits for that, but those are not exactly easy to adapt for *your* purpose17:44
wpwrakseems simple enough (?)17:44
DocScrutinizer05e.g. there's zilch measures to adjust the power17:44
DocScrutinizer05suuure >> WARNING: This can Kill Smaller animals, such as cats and rabbits, And Probably Even Small Children!<<< *exactly* what you need17:45
wpwrakthis one kills snakes: http://chemelec.com/Projects/Fencer-1/Fencer-1.htm17:46
wpwrak"don't try to bite off more than you can chew." never been more true ;-)17:47
DocScrutinizer05it's all exactly the very basic circuit I suggested in textual notation above, just with a transformer instead of a single choke17:48
DocScrutinizer05V+ ->choke->(electrode)->(IGBT||350V-Zener)->GND-(electrode)17:50
DocScrutinizer05duration you open up the IGBT determines the amount of energy stored in choke - or in your device as thermal energy when you open up too long17:51
DocScrutinizer05IGBT breaking the current will cause the energy in choke to go via electrode, whatever it takes to do that17:52
DocScrutinizer05unless the Zener kicks in, so you *really* need the Zener when your device fires with electrode NC17:53
DocScrutinizer05I can't think of a simpler (and worse designed) circuit17:54
DocScrutinizer05you at least should make sure that your MCU can't open the IGBT permanently17:54
DocScrutinizer05use a capacitor to couple the gate/basis to GPIO17:55
DocScrutinizer05this will limit the open-time to at least something17:55
DocScrutinizer05oooh, swap that17:56
DocScrutinizer05V+ ->(IGBT||350V-Zener)->choke->(electrode)->GND-(electrode)17:57
DocScrutinizer05dang, nope17:57
DocScrutinizer05V+ ->(IGBT)->(electrode)->(choke||350V-Zener)->GND-(electrode)17:58
wpwrak(choke vs. igbt) ah, i see17:59
wpwrakand yes, the basic concept always seems the same17:59
DocScrutinizer05you might want to conect electrode1 via a capacitor to choke*IGBT18:00
DocScrutinizer05to stop any current created from electrolytic of electrodes on wet skin18:00
wpwrakah, i see18:01
wpwrakokay, i think i have enough i to process at the moment :) (still a bit hung over from the weekend) thanks a lot !18:02
DocScrutinizer05can I have one of those? I'm pondering exactly same since years18:02
DocScrutinizer05wrist watch without display18:03
DocScrutinizer05still you always know the time exact to the minute18:03
wpwrakheh, need to see where that goes. a friend asked me if something with a vibration alarm could be built. it wouldn't actually be used as what we'd normally consider an "alarm" but rather to randomly interrupt the person wearing the device, which supposedly would help to enhance the person's ability to pay attention18:04
wpwraki fear the rationale behind that claim may reside deep in the metaphysical, though :)18:05
whitequarkI would find whoever made that device and strangle them in their sleep18:05
wpwrak"what time is it ?" "it's just been three jolts."18:05
wpwrakwhitequark: that was roughly my reaction as well ;-)18:05
DocScrutinizer05three jolts sounds like dyscordian18:06
DocScrutinizer05FFS they killed ddate18:09
DocScrutinizer05Name: util-linux18:14
DocScrutinizer05Version: 2.23.2-10.118:14
DocScrutinizer05>> Ab Version 2.23 ist ddate jedoch nicht mehr standardm├Ą├čiger Teil des Pakets.<< SUCKERS!!!!18:14
DocScrutinizer05#ifdef KILL_BOB18:20
DocScrutinizer05#ifdef US_FORMAT18:22
DocScrutinizer05    moe,larry,18:22
DocScrutinizer05    larry,moe,18:22
whitequarkshould've used #ifdef BRAINDEAD18:24
DocScrutinizer05jr@saturn:~/ddate> gcc ddate.c 18:27
DocScrutinizer05jr@saturn:~/ddate> ll18:27
DocScrutinizer05total 3618:27
DocScrutinizer05-rwxr-xr-x 1 jr users 22679 Apr 28 20:26 a.out18:27
DocScrutinizer05-rw-r--r-- 1 jr users 10421 Apr 28 20:26 ddate.c18:27
DocScrutinizer05jr@saturn:~/ddate> ./a.out 18:27
DocScrutinizer05Today is Pungenday, the 45th day of Discord in the YOLD 318018:27
DocScrutinizer05sudo cp a.out /usr/bin/ddate18:28
DocScrutinizer05meh, I'm a sissi. usr/local/bin/ddate18:29
DocScrutinizer05LOL    /*               note: EQUAL SIGN...hopefully that fixes it */18:33
qi-bot[commit] Werner Almesberger: cameo/templates/mkmk-simple: make $NAME.drl optional (master) http://qi-hw.com/p/cae-tools/671b74d20:59
qi-bot[commit] Paul Cercueil: Show the background while loading the menu (master) http://qi-hw.com/p/gmenu2x/dac1e4922:22
--- Tue Apr 29 201400:00

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