#qi-hardware IRC log for Wednesday, 2013-12-04

wpwrakwhitequark: (35 um) well, i thought that maybe they misplaced the decimal point. 00:49
wpwrakDocScrutinizer05: learn from the squirrels: they go out before it gets cold and dark and stock snacks.00:50
DocScrutinizer05squirrels are glorified rats00:51
whitequarkand birds are dinosaurs00:52
NickSydneyfound an interesting site http://www.explainshell.com/01:11
wpwrakNickSydney: interesting. but is the purpose to help or to intimidate ? :) if i didn't already know what  "true && { echo success; } || { echo failed; }"  does, i might think i'd never understand after reading the analysis ...05:54
qwebirc25409wpwrak: i guess the website is suitable for n00b like myself :)05:56
nicksydneywpwrak: can i use this kind of printer http://www.gumtree.com.au/s-ad/balgowlah/other-electronics-computers/brother-hl-2132-mono-laser-printer/1033007461 for doing my own PCB ?05:58
wpwrakhmm, some people say brother are bad for it: http://www.dutchforce.com/~eforum/index.php?s=11b10a8174e1d64372cd1da9d486fef6&showtopic=1887106:07
wpwrakbut then, maybe they didn't enough research on the paper and/or settings06:07
wpwraklinux / cups seems to be fine with it: http://crunchbang.org/forums/viewtopic.php?id=2289106:08
wpwrakin general, pretty much any laser that puts a significant amount of toner on the paper should do. so "eco" or draft modes may get in the way ... until you find out how to turn them off06:09
nicksydneyhmm06:11
wpwrakeach step of the process matters :) so the printer is one variable06:12
wpwrakthe paper is usually more critical. there's a lot that can go wrong there. you'll probably need to try a few different papers.06:13
wpwrakthis may be useful: http://www.almesberger.net/misc/led-toy/ledtoy-building-0pre9.pdf06:14
wpwrak(incomplete and old, but has more or less that complete process)06:15
wpwrakif you can get the HP C6039A paper, that would be best. not sure if it's still around, though06:16
wpwrakelse, you have to make a localized approach. you may also find help in local electronics enthusiast's fora06:17
wpwrakin general, google for printer name plus "toner transfer" (with the double quotes). that's likely to turn up experiences with that printer among the first hits06:18
wpwrakthen, print name plus linux to see if it's friendly06:18
wpwrakhere are some examples of what the results of printing and transfer should look like: http://downloads.qi-hardware.com/people/werner/tmp/paper/06:21
wpwrakyou may also want to get a permanent marker with a very fine tip, to cover any spots where traces got interrupted in the print/transfer. (like the ones marked red at the bottom of the left column)06:23
wpwrakif you miss any of these things you can also fix them with solder, but it's more convenient if you don't have to06:24
wpwrakah, and regarding the instructions, i wouldn't use ferric chloride anymore. nowadays i use muriatic acid with peroxide. cheaper, easier to get, cleaner, faster. drawback: not so nice to do indoors.06:26
nicksydneywpwrak: that doc is really thorough09:58
wpwrakthe soldering part is a bit obsolete. back then i stoll thought ssop were kinda difficult. nowadays, i solder them by just "painting" the solder. quicker and safer than the process i described there.10:50
DocScrutinizer05muriatic acid?11:30
wpwrak"salzsaeure"11:33
wpwrakHCl + H2O2 is a LOT better than ferric chloride. you can find the ingredients everywhere, it's a clean liquid and it stays clear (unlike FeCl with all the black sludge building up in there), it works perfectly at room temperature (FeCl: wants heating), and you can just store and reuse it11:35
wpwraki keep mine in a glass jar with a flat bottom and a tightly fitting plastic cover. that way i don't have to move it between storing and etching. if it gets weak, i add a bit of peroxide or acid. every year or so, when the volume gets too large, i put a bit into a larger kjar. so this means basically no residues. (until i want to dump the large11:37
wpwrakjar, but that one also has its uses for bigger items)11:38
wpwrakto keep the volume increase low, i use 35% peroxide to "reactivate" the mixture.11:39
whitequarkwpwrak: peroxide is a regulated substance in quite a bit of countries afaik, it being a precursor11:40
whitequarkoh and muriatic acid too11:40
wpwrakwell, peroxide at a low concentration is a desinfectant. you should be able to get at least that (at any pharmacy). the stronger stuff may be more difficult11:41
whitequarkyes, I think peroxide is 15-30ml max11:41
whitequarkand it's not concentrated at that11:42
wpwrakmuriatic acid should be at any hardware store :)11:42
whitequarkno11:42
whitequarkit's a precursor11:42
whitequarkhere you can only buy via bank transfer from a company account11:42
wpwrakyeah, the weak peroxide will do. you just ,ay not be able to reuse it so well11:42
whitequarksame for KMnO4 and pretty much any interesting compound11:43
whitequarkexcept probably diluted H2SO4 which is used in Pb rechargeable batteries11:43
wpwrakHCl ? you should come to argentina and buy a few canisters of it ;-)11:43
whitequarkyeah, good luck transporting that back :p11:43
wpwrakhcl is used to balance the acidity of swimming pools. so pool supplies may be a place where you can find it11:44
whitequarksee above, bank transfer from a company account11:44
wpwraki think it's also used for pipe cleaning or such. maybe you can find something that's 99.9% HCl, 0.1% perfume, and has an innocent-sounding name ;-)11:45
whitequarkwell, I think I could buy HCl if I ask around and find someone not related to retail, i.e. ask directly at the factory11:45
whitequarkthere has been wide reports of success this way11:45
whitequarkbut it's by no account "easily obtainable"11:46
wpwrakokay, not in russia then11:46
mthI thought pipe cleaning was done with bases rather than acids? or are both possible?11:48
wpwraki heard that story of, one upon a time, cotton barons lobbying for banning hemp on the reason of its potential use as a drug, to get rid of the competition. maybe something like that happened with HCl in russia11:49
whitequark^ yeah, here concentrated NaOH is used for that11:49
wpwrakmth: i don't know really what they use it for. i just know there's half a rack full of it in the plumbing section, bottles of 1 l and canisters of 5 l11:50
wpwrakthat is, it looked like that about a year ago or so. i have some 7.5 l stocked (i'm not quite sure what i thought back then i'd need all that stuff for), so with an annual consumption of about 1-2 dl, i'm beginning to get interested in longevity research11:58
sanderrWhere do you go with the used fluids?12:06
wpwraki'd take off the lid and leave the jar outside. that why the water evaporates and i get a small quantity of solids. these go in the trash.12:09
wpwrakbut most of the liquids can just be reused. you only need to discard them if they get contaminated with something.12:10
wpwrakin the absence of contamination, i.e., if you discard a batch because its has gotten overly diluted, you could probably also recycle the solids.12:11
sanderrOk, that's clear. :)12:24
wpwrakwhen you let it dry, it forms pretty blueish-green crystals. much nicer to look at than the black-brown sludge FeCl becomes. plus, if your neighbours have seen "Breaking Bad", you can tell them you're improving on Heisenberg's formula :)12:44
whitequark*g*12:44
wpwrak(well, don't tell them in they're likely to try to get a sample :)12:45
wpwraks/in/if/12:45
mthwpwrak: be careful that your container lasts that long; my father had kept old photography chemicals and many years later the plastic bottle started leaking12:48
whitequarkin my experience plastic (polystyrene) lives under a year. after that, it becomes extremely brittle, but doesn't leak very much until you try to touch the bottle.12:49
whitequarkit is ostensibly acid-resistant, and the basic chemical probably is, but then there's plastificator12:51
wpwrakmth: i have plastic bottles in a plastic box stored outside (on a ceramic floor, a good distance from the drain)12:54
wpwrakneed to replace the box, though. it didn't like the last storm ...12:54
wpwrakthe bottles are several years old. and yes, they feel a bit brittle. the main problem isn't liquid leakage but gas leakage. i had one under the kitchen sink for a while. then i noticed that all the metal parts in the area were heavily oxidized. than's when it moved to the terrace.12:57
DocScrutinizer05haha14:25
DocScrutinizer05yeah, you should probably put bottles with corrosive liquids into a larger airtight box with some passivator or absorbant stored in the box as well14:26
DocScrutinizer05e.g a dish with naOH14:27
DocScrutinizer05NaOH even14:27
DocScrutinizer05or some other alkali substance14:28
sanderrThere's so much fun in open hardware. You learn about chemistry, electronics, computer science, mechanical engineering and everything in between. :)15:40
sanderrEven human psychology.15:40
larscand economy15:42
DocScrutinizer05and a lot about medical treatment ;-)15:55
whitequarkoh?15:58
larscre-attaching limbs and such ;)16:01
DocScrutinizer05yeah, burns, scratches, cuts, injury from various chemicals...16:05
DocScrutinizer05curing with other chenicals ;-) (acrylate works great for small cuts)16:06
DocScrutinizer05(also for broken nails)16:06
whitequarkhnggg broken nails :/16:07
larscsilver nitrate16:07
DocScrutinizer05eew16:07
DocScrutinizer05yeah that's nasty16:07
DocScrutinizer05though rather rarely needed in electronics16:08
larscgood for sealing wounds though, the color takes a while to wash though16:08
DocScrutinizer05hmm, I guess you can use alaun for that16:09
DocScrutinizer05less agressive and toxic16:10
wpwrakDocScrutinizer05: (airtight box) naw, they're free to gas out into. the wind will take care of them. and i wouldn't want to have a passivator that has an exothermical reaction in there. having one bottle leak is one thing, melting holes in all of them and the outside container is quite something else :)16:12
DocScrutinizer05ooh, english term is alum16:13
DocScrutinizer05hmm yeah16:13
DocScrutinizer05you probably want to use a passivator that's not that reactive16:14
DocScrutinizer05a few shells or sth like that16:14
wpwrakif it gets out, i'll be exposed to evaporation :) if it gets out in the middle of a thunderstorm, it'll  be massively diluted before it goes down the drain16:15
DocScrutinizer05nah, i'm talking about storing such stuff indoors16:16
DocScrutinizer05corrosion of all metal in reach of acid bottles is a known problem, which you can counteract by wrapping the acid bottles into something to passivate the fumes16:17
DocScrutinizer05maybe a cloth you tintured with baking soda may do16:19
DocScrutinizer05tinctured*16:19
wpwrakhmm, i think i'll leave it just outdoors :)16:21
DocScrutinizer05 Natriumhydrogencarbonate actually, you don't want the acid in it16:21
rjeffrieswpwrak something to consider for anelok V2: http://techcrunch.com/2013/12/04/the-next-gen-usb-plug-to-be-smaller-and-finally-reversible/ (It's A Good Thing, smaller & REVERSIBLE!)16:22
DocScrutinizer05sure, outdoors is always a safe bet (unless you face other threats when you keep it there)16:22
DocScrutinizer05WTF?16:23
DocScrutinizer05OMG!16:25
DocScrutinizer05USB Type-C16:25
DocScrutinizer05God forbid!16:26
DocScrutinizer05why did EU and China say "charging only via USB", anybody?16:26
wpwrakand there i was, already feeling a bit bad about using micro when the world is still largely using mini :)16:27
DocScrutinizer05Seems we soon have more USB connector types than we used to have barrel connectors16:27
rohwell.. lets see what happens. reversible, 100W OD... sounds too good. but if they make it work, could be nice16:27
wpwrakcharging over USB makes a lot of sense since it's a nicely standardized interface. so far the theory ...16:27
rohs/OD/PD16:27
wpwrakroh: 110 V, 1 A ? ;-)16:28
rohwpwrak: dunno exactly16:28
DocScrutinizer05mybe 50V 2A16:28
rohbut they spec-ed 90W on poe 802.3at16:28
roh50-70V or so then.. on multiple pairs (all of them)16:29
DocScrutinizer0542V 2.5A16:29
rohone speaks lldp with the switch to discuss power requests when one needs more than 13.5W16:29
DocScrutinizer05isn't USB3 some 35V?16:29
Action: DocScrutinizer05 honestly wonders when those standard-inventing dummies consider doing a *nice* one, with just golden pads and magnets under it16:33
DocScrutinizer05magnets in the plugs only, while devices have ferromagnetic material. and the plugs need a button to "short" the magnet internally, so any magnetic debris falls off the plug16:35
DocScrutinizer05maximum easy attaching of plugs to devices, even in cradle. easy removal, non-destructive even when done wrong16:38
DocScrutinizer05and when you actually allow magnets in both the plugs and the devices, then you can even get very flexible coding of which plug matches where16:40
DocScrutinizer05a 3pole plug will just jump into place to a 8pin attachment field16:41
wpwraki kinda doubt that magnets should be part of the solution. at these sizes, they would have to be terribly strong to hold the connector in place16:42
DocScrutinizer05you don't need insane microscopic plugs like 1.5mm barrel or micro-USB16:43
ysionneauwin 4716:43
DocScrutinizer05with this sulution your plug cab be 5mm high and 20mm wide16:43
wpwraki do :)16:43
wpwrakysionneau: an no, you don't win ;-)16:44
ysionneau:(16:44
ysionneaunext time maybe!16:44
DocScrutinizer05the problem why manufs want small plug formfactors is they want small holes16:45
DocScrutinizer05actually they want no holes ideally (I *hear* Sean ;-P) - with that type of connector they can get that, so no more need to miniaturize16:46
ysionneauFYI if you are interested in buying a Milkymist One R3.5 or a Mixxeo board, please fill in this doodle: http://doodle.com/sbdnetqi4mrf7w9i16:46
rjeffrieswpwrak microUSB is FAR more common than miniUSB. Another factoid: microUSB allows far more plug/unplug cycles 16:47
ysionneauI'm gathering names, if I get enough (10?) names I can seriously think about starting another production run16:47
wpwrakrjeffries: (more cycles) at least that's what the spec says. i kinda wonder how they reach that conclusion, though :)16:48
wpwrak(more common) dunno. seems that all the spartphones are now micro. but all the rest still seems to be mini.16:49
wpwrakDocScrutinizer05: they also want small devices. else you're talking about the other Qi: http://en.wikipedia.org/wiki/Qi_(inductive_power_standard)16:50
rjeffriessmartphone unit volume totally swamps any other use case by factor of what ? 1000 or 1,000,000 get serious. LOL16:50
wpwrakregarding connectors, this one gets high praise for its clean mechanical design: http://en.wikipedia.org/wiki/Lightning_(connector)16:50
wpwrakso maybe in 2032, when the patents expire, usb 7 will have nice connectors :)16:50
rjeffriesyes Apple's Lightening is sweet connector. Too bad it is not opne...16:50
rjeffriesApple also has THE best power connector on their laptops, by a few kilometers16:51
wpwrak(volume) i still have a lot more devices that aren't phones than devices that are phones :)16:52
DocScrutinizer05wpwrak: (small devices) so what, thinner than 4mm? smaller than 20mm?16:55
DocScrutinizer05the device that *nowhere* has a free area of at least 5*20mm is yet to get built, and I guess when it gets built, no micro-USB will fit in ;-)16:57
wpwrakmaybe 20-50 mm for the sides, 5 mm for the thickness. that's about what you can do with Micro USB while still having something else in your device16:57
wpwrakyes, 20x5 mm would be about sufficient for micro16:57
DocScrutinizer05ehß16:57
DocScrutinizer05?16:57
wpwraka micro receptacle is 3 mm tall. add a bit of clearance and a thin plastic case and you have 5 mm16:58
DocScrutinizer05so what?16:58
rjeffrieswpwrak my perspective is not "what wpwrak has in his lab such as dev boards etc." but how many GAZILLION "things" in teh world use microUSB. It is a non-trivial delta with several zeros after the leading "1"16:59
rjeffriesDocScrutinizer05 bless you sir, we understand that Neo900 is not designed as a thin and light device. many (almost all) current high-volume handsets are. so to each his or her own. compavt connectors are indeed a thing. ;)17:00
wpwrakhmm, midi instruments, full-size B or mini-B. digital camera mini-B, keyboard mini-B, RF keyboard, mini-B. okay, they all happen to be in my lab, but that's just because that's where i am most of the time :)17:01
DocScrutinizer05WTF?17:01
DocScrutinizer05how comes Neo900 in here and now??17:01
DocScrutinizer05>:-(17:01
rjeffriesNeo900 is a cool device. It really is!17:01
rohrjeffries: maybe the connector is nice, but the cables are shit.17:01
wpwrakDocScrutinizer05: i think he's congratulating you on using a sturdy 6.3 mm audio connector ;-)17:01
rohlots of broken apple psu around here17:02
rjeffriesall cables are shit17:02
DocScrutinizer05and so are Porsche, so what?17:02
rohthey always break next to the connector/psu17:02
rohi havent had that problem with my lenovo psu.17:02
rjeffriesNeo900 was not designed in an era when thin and light was the gold standard. and that's OK.17:02
DocScrutinizer05yes, so what?17:03
rjeffriesam I mistaken? maybe Neo900 does use microUSB? if so, my apologies17:04
DocScrutinizer05how's that related to magnetic plugs that don't have to get inserted to devices?17:04
rjeffriesmagnetic connectors are a cool idea. I misunderstood (maybe) that you disapprove of microUSB. anyway, enough elctrons have been consumed.17:05
wpwrakthat's the complementary Ford approach. he sent his men out to find parts that still looked good in discarded cars, so that he could make them less durable. apple fix the part users complain most about, then weaken something that used to work :)17:05
DocScrutinizer05which admittedly would need more surface on device than a microUSB17:05
DocScrutinizer05but I think that's irrelevant, for afore elaborated reasons17:06
rjeffrieswpwrak ha dnot heard that Henry Ford story. Love it!17:06
wpwraki probably have it from Dawkins. search for "Ford" on http://www.environmentfoundation.net/reports/richard-dawkins-main-speech.htm17:09
DocScrutinizer05rjeffries: I said "yes, you need more area than a micro-USB or similar tiny connector needs, so you get magnets of sufficient strength. But that's irrelevant since devices have enough free surface to attach a 20*5mm magnetic contact there. And divices that are smaller than 20*5mm won't have a micro-USB anyway". wpwrak answered "no, 20*5mm is a KO criterion for that idea since OEM want to build small devices"17:11
DocScrutinizer05NB that a 10 pole magnetic connector device-side would need less volume than a micro-USB receptacle17:14
wpwrakwould it ? you still need the contact surfaces (which could be shallow, so there you save volume) but then the metal blocks on which your magnets pull17:16
DocScrutinizer05blocks? I think a 0.2mm ferromagnetic layer is sufficient17:19
DocScrutinizer050.2mm steel covered with the usual NiCuAg17:19
DocScrutinizer05embedded into the plastic case shell17:20
DocScrutinizer05a 1mm Neodyme magnet at one contact to fix orientation17:21
DocScrutinizer05thinking about it, I guess the whole thing needs 0.0 .. 20mm^3 volume, given you replace parts of the plastic shell with it17:23
wpwrakhmm, i wonder how thin you can make a ferromagnetic layer before it stops working as such. there ought to be some F = X*f(d)   where X is surface, field strength, and such, and f(d) is a monotonously increasing function of the thickness of the ferromagnetic sheet17:27
whitequarkvery thin metallic foil is still highly magnetic17:29
whitequarkbut, the force can be negligible17:29
DocScrutinizer05depends on saturation17:34
DocScrutinizer05eventually all atoms are polarized 8oriented) and the magnetic force will not increase much17:35
wpwrakisn't it more like how much of the field is absorbed by the ferromagnet ?17:35
DocScrutinizer05what means "absorbed"?17:36
wpwraki.e., when you add arbitrarily thin sheets until the force on the last one added is below a threshold, then you have the thickness at which the corresponding portion of the magnetic field is used17:36
wpwraki'm basically saying that shielding == magnetic force. not sure how close this is to reality17:37
DocScrutinizer05yes, that's when enough atoms of the ferromagnetic marerial are polarized to deviate and guide the magnetic field away from the next layer17:37
wpwrakyup17:39
DocScrutinizer05when you got a ferritechoke and you increase the current and thus magnetism, it at one point gets saturated and magnetic field escapes from the ferrite core17:39
wpwrakso i would expect the force to increase with thickness. of course not linearly. more like a log curve (too lazy to look up the right sort of function)17:40
DocScrutinizer05prolly it does17:40
wpwrakso the question is how much ferromagnet you need before you only get diminishing returns17:41
DocScrutinizer05you recall the cig paper magnet thingie I linked photos in here? the ferromagnetic patch is like 8*4mm and maybe 0.3mm thick. The force from that tiny neodyme magnet to this thing is in the 50g range (guessed)17:43
wpwrakhmm, not bad17:44
DocScrutinizer05the magnet itself is so thin it doesn't really show when embedded into the carton of the cover17:44
DocScrutinizer05maybe 1mm17:45
DocScrutinizer05maybe 1.517:45
wpwraknow you need to calculate the forces acting on the connector. cable weight, any pull caused by movement, then the lever effect of the plug17:48
wpwrakfor the lever, you probably have a radio of 1:5 to 1:1017:48
wpwraks/radio/ratio/17:49
DocScrutinizer05make the "plug2 thin and the cable flexible17:49
DocScrutinizer05this of course defeates the "off-button" idea for the magnets17:49
wpwrakyou mean "breakable". do you moonshine for apple ? ;-)17:50
DocScrutinizer05eh?17:50
wpwrak(off-button) yeah, that one's classical german over-engineering ;-)17:50
DocScrutinizer05breakable like "you can bend it by brute force"?17:50
wpwraknaw, flimsy so it's light17:51
wpwrakremember that you may have some 1-1.5 m of cable hang off the connector.17:51
DocScrutinizer05what's flimsy with a 0.5mm steel ?17:51
wpwraki mean the cable ;)17:52
DocScrutinizer05sorry, afk17:52
DocScrutinizer05no, i mean to use silicon isolation instead crappy hard PVC, proper fine copper braid, and a steel wire for increased strength17:58
DocScrutinizer05there are cables strong and flexible like wool string17:59
DocScrutinizer05tronger probably18:00
DocScrutinizer05stronger18:00
wpwrakthe industry seems to agree that USB cables are weightless18:01
wpwrakyeah. none specify the mass.18:09
whitequarkquick, make a time machine!18:11
wpwrak54, 30, 12 ... so about 40 g for a total of 1 m cable plus a total of four usb-micro plugs18:13
wpwrakso you get a pull of about 60 g on an 1.5 mm cable. add lever and you magnet needs to be able to hold roughly a 0.5 kg force18:14
wpwrakadd some margin and handling tolerances (e.g., if the user moves the device while attached) and you're at 1 kg18:15
DocScrutinizer05no way18:15
DocScrutinizer05this is a connection and not a stand18:15
wpwrakdon't forget the lever18:16
wpwrakthat is, unless the connector rotates freely :)18:16
DocScrutinizer05heck you're mad, with 500g perpendicular force I rip each micro-USB receptacke off the PCB18:16
DocScrutinizer05honestly, I dunno if you're trolling me18:17
wpwrakno, it's < 100 g perpendicular18:17
wpwrakbut your contact surface is parallel to the connector surface. and one side will be small, hence the large lever18:18
DocScrutinizer05nonsense, I told you the "plug" is lower than wide18:18
wpwrakyou mean shorter ? (distance from case)18:19
DocScrutinizer05and the distance between contacts and cable exit point maybe 1mm, maybe less18:19
wpwrakyou still have the cable's bend radius18:20
DocScrutinizer05which is like 5mm max18:20
wpwrakmore like 5-10 cm 18:20
DocScrutinizer05for whatever crap you assume18:20
wpwrakwith liquid helium, you get better flexibility, i give you that :)18:21
DocScrutinizer05yeah, trolling. Now I'm sure about that at least18:22
wpwrak"WARNING: do not expose to excessive heat (> 1 K)"18:22
Action: DocScrutinizer05 wonders if wpwrak ever used headphones. Decent ones with a good cable18:22
wpwrakyou can try it: take a micro usb cable, balance the plug on a finger tip. then add a weight on the exposed connector until it's more or less horizontal18:23
DocScrutinizer05not those which pop out of your ears when you push the cable18:23
wpwrakthen you can calculate the force you're counterbalancing18:23
DocScrutinizer05DAFAQ micro-USB cable!!!18:23
DocScrutinizer05PVC shit!18:23
DocScrutinizer05cheap crap18:23
DocScrutinizer05and when I use a power cord I get a radius of 50cm18:24
wpwraklet's see if the pvc matters ... density is about 1.2 g/cm318:25
Action: DocScrutinizer05 headdesks and heads out18:25
wpwrakhow thick shall we assume the pvc is ? 0.5 mm ?18:32
wpwrakso the jacket (cylindrical) is about 5 mm^2 18:34
wpwrakper meter that's .... 5k mm^3, or 5 cm^318:34
wpwrakso about 6 g. reducing the estimate for the 1.5 m cable from 60 g to 50 g if using weightless neojoergodyne instead18:36
wpwrakso that's still a 0.4-0.8 kg force18:37
wpwraknow, balancing a 0.5 mm usb cable, i need at 20 mm a weight of ... 62.6 g18:43
wpwrakso about 1.2 mNm18:44
DocScrutinizer05now please do the same for carbonfibre-resin18:50
DocScrutinizer05or better: glass18:50
wpwrakerr, make that 12 mNm. g = 10 N/kg, not 118:51
wpwraki already assumed it's weightless18:52
DocScrutinizer05I bet fibre-resin must have about  the same specific weight as PVC (remarkably irrespective of the amount of softener in PVC)18:52
wpwraknow, if the force of the ... how tall was it ... 5 mm ? connector was about uniformly distributed, that would be 2.5 mm. so the magnet's holding force would have to be at least ... about 5 N for the 0.5 m cable18:52
DocScrutinizer05yeah, and when the moon was made of chestercheese18:53
wpwrakso for 1.5 m we get 15 N. you estimated the 8x4 mm patch to have about 0.5 N18:53
wpwrakcan you actually measure it " attach some variable weight an see how far you can go until it separates18:54
wpwrakthen measure the weight18:55
DocScrutinizer05I bet in 30 minutes you proved mathematically that you can't bend a knot ito a bamboo stick18:55
wpwrakwell ... let's be generous. the bending radius will be reduced by having more weight in it, so let's say you need only 10 N18:56
wpwraklet's also assume you underestimated your magnet by a factor of 2 and it actually pulls 1 N18:56
DocScrutinizer05just *one* small hint: my "plug" is 20*5*3mm, and the cable comes out at the 5*3mm small end18:57
wpwrakthis still means that you need a patch of about 12 x 24 mm.18:57
DocScrutinizer05and just maybe my cable is made of FPC18:57
DocScrutinizer05so 4mm wide and 0.3mm thick18:57
DocScrutinizer05and it has a bend radius of 2mm18:58
wpwrakFragile Perishable Crap ? :)18:58
wpwrakyes, if you reduce the cable to nothing, then it works rather well :)18:59
wpwrakremember openmoko and the FPC fun with the debug board ? those were about 10 cm with usually very careful handling. i wish thee luck ;-)18:59
DocScrutinizer05remember I said *maybe*19:01
DocScrutinizer05I'm honestly bored about this discussion19:01
DocScrutinizer05[2013-12-04 18:58:32] <DocScrutinizer05> no, i mean to use silicon isolation instead crappy hard PVC, proper fine copper braid, and a steel wire for increased strength19:01
DocScrutinizer05and now, to annoy you, I reinforce my "crappy FPC" with a stainless steel fabric from both sides19:02
wpwraki subtracted the weight of the outer PVC. so all that's left are the metals and the inner isolations19:02
wpwraklet me think of someone i really hate. someone you should hire for the customer complaints department :)19:03
DocScrutinizer05why me? I thought YOU will build those things19:04
DocScrutinizer05but yeah, we know you love to troll and criticize19:04
wpwrakindeed ;-)19:05
wpwrakand no, i'll stick with micro USB. let people complain to the USB-IF :)19:05
DocScrutinizer05they probably will complain that the USB plug is larger than your Y-thingie19:10
whitequark /rename #angry-joerg-ranting19:11
whitequark:p (not that I mind)19:11
DocScrutinizer05sorry, watching pages of meaningless math makes me feel like that19:12
whitequarkI really don't mind, it's fascinating to watch19:12
DocScrutinizer05and it's not like I suggested to replace the mcro-B-plug at the end of an existing crappy cable by something that looks similar but works kinda different. I tried to explain and discuss a concept19:14
arielenterwpwrak: Thank you very much for all your help, I'm probably will be joining this community soon. Thanks again and see you around :)21:54
wpwrakarielenter: it was a pleasure. and welcome to the club ! :)22:11
DocScrutinizer05https://www.olimex.com/ (Fr 29. #35 challenge maze) *YAWN* we coded this 1977 on the HP-2522:17
DocScrutinizer05http://www.hpmuseum.org/25.jpg22:18
DocScrutinizer05uhh, NOW I get it - at least I thin I do. Looking at https://www.olimex.com/Products/ARM/ST/STM32-E407/open-source-hardware upper left corner22:22
DocScrutinizer05(#35) OOPS, I read that cursory, and now I see I missed the changed goal of this one22:26
wpwrakDocScrutinizer05: submit your hp25 solution. you'll probably win :)22:58
DocScrutinizer05it's for a different problem, called "xray" maybe23:00
DocScrutinizer05you send in a beam and it gets deviated 90° when you hit a impority one-off. and it gets absorbed if you hit the imurity without offset23:01
DocScrutinizer05you see where beam comes out (if it does) when you send it in23:01
DocScrutinizer05kinda like minesweeper, just a tad more smart23:01
DocScrutinizer05dang, lemme try it once with ALL the RIGHT letters in it: impurity23:05
wpwrakah, so you'd even use fractional coordinates23:07
wpwrakmodern language is complicated. great Maxwell simply called it his "demon" :)23:47
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