#qi-hardware IRC log for Tuesday, 2014-01-14

whitequarkDocScrutinizer05: relevant: http://www.reddit.com/r/askscience/comments/1v1u0a/solubility_of_gasses_in_substances/ceof7qt?context=302:22
whitequarkalso, solubility of gasses in liquids does not, in general, decrease with t°! I've been lied to my entire life. J. Chem. Ed. 1955, 32(8), 399; http://i.imgur.com/2fdxZEg.png02:30
DocScrutinizer05my world collapses02:55
whitequarknot sure if sarcasm :)02:57
DocScrutinizer05no kidding, just a tad of exaggeration03:01
DocScrutinizer05I'm actually amaced how much I seem to have tickled your curiosity03:02
DocScrutinizer05amazed even03:02
nicksydneywpwrak_: open source thermostat perhaps next project http://www.ifixit.com/Teardown/Nest+Learning+Thermostat+2nd+Generation+Teardown/13818 :)03:03
DocScrutinizer05sure, it's pretty clear that in the end everything is about energy and entropy03:03
whitequarkDocScrutinizer05: I tend to get sidetracked on fundamental-y things. The whole reading encyclopedias from cover to cover thing :)03:04
whitequarkI think I started seriously reading up on LLVM not because I had a language to implement, but simply because I was fascinated by it so much.03:08
DocScrutinizer05on a loosely related topic I find intriguing: all about boiling delay, hypothermic liquids and the question why sodawater bubbles come up on a ricecorn you throw in the glass03:09
whitequarkhypothermic liquids? you mean supercritical?03:09
DocScrutinizer05like handwarmers03:10
whitequarkuh, no, probably not03:10
DocScrutinizer05the stuff with the liquid salts at room temperature03:10
whitequarkgot it. I'll remember the right term in a moment03:10
DocScrutinizer05that all of a sudden crystallize when you bend that clickdisk03:11
DocScrutinizer05in german it's "unterkuehlte schmelze"03:11
whitequarkit's "supercooled liquid" in english03:11
whitequarkaka "undercooled" but I think "supercooled" is more common03:11
DocScrutinizer05btw glass also is such a stuff03:11
whitequarkglass is an amorphous solid03:12
whitequarkor do you mean something else?03:12
DocScrutinizer05just glass doesn't tend to spontaneously crystallize03:12
DocScrutinizer05only very very slowly03:12
whitequarkI don't think glass crystallizes at all?03:13
DocScrutinizer05also glass flows, but very very slowly, so it's actually liquid03:13
whitequarkglass doesn't flow, it's a common misconception :p03:13
DocScrutinizer05yes, it does, after hundreds or thousands of years03:13
whitequark(glass crystallization) glass, by *definition*, is a solid which is not crystallized03:13
whitequarkDocScrutinizer05: source?03:13
DocScrutinizer05common kowledge about e.g. windows in churches03:14
DocScrutinizer05and glass defects getting worse in very old drinking glasses03:14
DocScrutinizer05might be another lie they told me03:15
whitequarkit's an artifact of the manufacturing process which has been used back then. you'd blow a bubble of glass and then flatten it. naturally, an edge would be more thick. they were then customarily placed with the thick edge pointing down.03:15
whitequarka very common misconception indeed03:15
whitequarknever heard about glass defects though03:15
DocScrutinizer05I heard it starts crystallizing just like that pocket warmer salts, just in ultra slow motion03:16
whitequarkI think the very composition of glass prevents it from crystallization03:16
DocScrutinizer05possibly correct for contemporary glass03:17
whitequarklemme find you some sources03:18
DocScrutinizer05anyway the term "unterkuhlte schmelze" I heard first time in relation to glass03:18
whitequarkDocScrutinizer05: ok, "Do Cathedral Glasses Flow?", Am. J. Phys. v66, pp 392396, May 199803:21
whitequarkorrr Plumb, R. C. (1989) Antique windowpanes and the flow of supercooled liquids. Journal of Chemical Education, 66(12): 994-996.03:21
whitequarkthis has some more explanation and references: http://dwb.unl.edu/teacher/nsf/c01/c01links/www.ualberta.ca/~bderksen/florin.html#plu03:22
whitequarkbtw the first article is free-access, www.df.unipi.it/~leporini/DFWebSite/ReviewsTg/CathedralGlasses.pdf03:22
whitequarkfor the defects in drinking glasses I'd need more context03:24
DocScrutinizer05well, that article actually admits that glass flows03:27
DocScrutinizer05just way more slowly than usually assumed03:27
whitequarkrelaxation time is higher than the age of universe03:29
whitequarkthis kinda stretches the definition of "flows"03:29
whitequarkthough you are correct to some extent. let me find the pdf for the second one.03:29
wpwrakit's the proton decay that makes them flow03:32
Action: wpwrak ducks03:32
whitequarkDocScrutinizer05: http://rghost.ru/51637223 pdf03:32
whitequarkit mentions two phenomena (zero-creep and anelasticity) which resemble viscous flow in glasses but are not identical to it03:35
whitequarkhighly fascinating read03:35
whitequarkalso, it has an amazing description of the ancient glass-making process03:36
DocScrutinizer05sorry, getting late here03:37
whitequarksure, take a look when it's convenient03:37
DocScrutinizer05cation diffusion, incredible04:15
Action: DocScrutinizer05 considers glass like a sponge from now on ;-D04:15
whitequarkooooh yes, cation diffusion allows for a very neat trick04:26
whitequarktake a thin glass "wire", so thin you could bend it more or less freely, and make it in a spiral, then let it sit for a few days04:26
whitequarkyou could then just play with this glass spiral, it'll remain more or less in the same shape04:27
whitequarkbut if you place it on top of liquid Hg, it'll begin to rapidly regain its original shape04:27
whitequarkcan't seem to find anything on youtube04:28
DocScrutinizer05hmm, cation diffusion should be susceptible to electric current, no?04:37
DocScrutinizer05sort of electromigration causing anelastic deformation of glass when sending electric current through it04:37
whitequarkthat sounds plausible, but...04:39
whitequark"Conduction mechanism in ionic glasses is still considered one of the great challenges in physics and chemistry of glasses [A. Bunde, K. Funke, and M. Ingram, Solid State Ionics 105, 1 (1998)]."04:39
whitequarkalthough, let me read it04:40
whitequarkconduction in glasses.1,5 Nowadays, everybody seems to04:41
whitequarkagree that ionic conduction in glasses, at least in the dc re-04:41
whitequarkgime and in the ac regime at not too high frequencies, is due04:41
whitequarkto hopping of ions between localized states in the glass04:41
whitequark1,5matrix. However, the mechanism of such hopping is the04:41
whitequarksubject of many controversies.04:41
Action: DocScrutinizer05 thinks of a glass rod with two steel wires along it04:41
DocScrutinizer05then heating it up till it starts conducting, and feeding a good current through it, not axially04:43
DocScrutinizer05should bend, eh?04:43
whitequarkinteresting, it suggests that the ions in glass may act as charge carriers in semiconductors (!)04:43
whitequarkwith a bandgap region04:43
whitequarkI dunno, it well might04:43
DocScrutinizer05hehe, glass, the hottest semiconductor ever04:43
whitequarkah, no, the semiconductor thing was actually ruled out04:44
wpwrakhmm, does this (incomplete) layout look reasonable ? http://downloads.qi-hardware.com/people/werner/anelok/tmp/ybox-draft-20140114.png06:02
wpwrakespecially regarding the RF side06:02
wpwrakit's the new ybox, with a little kl25 and a cc2543 hopefully BTLE-capable transceiver06:03
wpwrak(incomplete = some vias missing, not fully routed, no ground fill. i think all the components are on the board)06:04
wpwrakah, and i need to do the board cut-out for the usb receptacle :)06:06
wpwraksize of the PCB is 59 x 19.2 mm so the full device will be about 61.4 x 21.6 mm06:11
rohwpwrak: there seem gaps in the antenna.. are those on purpose?06:27
wpwrakrendering artefacts :)06:29
wpwraki wish i could make the critter smaller. but things get very messy if i try to put the chips on the bottom side06:49
wpwrakhmm. just realized that i need to make the board a little wider or i won't have enough room for milling the corners in the case06:52
wpwrakhmm. of course, if i keep the top-mounted usb receptacle, ugly monster that it is, then i could cram a lot of stuff under it ...07:34
whitequarkoooo, I found out how the printer determines the amount of toner in the cartridge07:44
whitequarkit's a very fascinating purely mechanical thingy07:44
whitequarksee that white lever in bottom right corner? that's how. it kinda rotates around on its axis07:45
whitequarkon the spent cartridge it's in far right position. on the new one, in the far left07:45
larscapelete: that "... busy" messages are not normal, unless you have debugging enabled in the dma framework07:59
larscapelete: you don't need a filter function, all channels can be used for everything07:59
whitequarkit is amazing how much better this laser printer now prints, now that I have cleaned the drum thoroughly08:12
whitequarkby the way, the manual says you should do it with dry cotton swab, but it had something like 0.2mm of toner attached to it in some places, so I went for a wet cloth08:13
whitequarkthat works perfectly08:13
whitequarkafter/before: http://imgur.com/Aue7Kjm,eywYHoO08:17
larsca friend of me who works as a IT service tech recently told me that she was asked why the laser printer even needs toner, apparently the person who was asking was under the impression that the printer would use the laser to burn the paper08:21
whitequarkwell, it's not a completely outlandish concept08:26
whitequarkI mean, if the person doesn't have tech as their core competency, I don't see anything wrong with that guess. Internals of laser printers are not exactly trivial, especially to laymen.08:27
larscyea, I thought it was funny who the name is misleading08:29
larscfor a inkjet printer the name tells you basically who it works08:29
whitequarkoh does it? http://imgur.com/LDRTh7p08:32
whitequarkthat would also explain why are they so noisy and need sometimes several minuets to start up!08:33
viricdo laser printers actually have a laser? :)08:39
viricI never tried to understand how it works08:39
whitequarkviric: it's conceptually simple. it has a drum covered by selenium inside and a high-voltage generator08:40
whitequarkinitially, the entire drum surface is charged. then, a rotating mirror and a laser are used to direct light to those areas which need to be white, discharging them via the photovoltaic effect08:41
viricI thought the drawing wouldn't involve mechanical parts08:41
whitequarkthen, the toner is fed to the drum with another rotating cylinder, and the toner clings to the drum where the latter is charged08:42
viricmechanical moving parts. :)08:42
whitequarkthen, paper is pressed against the toner, transferring it to the paper08:42
viricI knew the static electricity part. But not how that is achieved.08:42
whitequarkthen, paper is fed through two hot cylinders pressed against each other, melting the toner and making the paper absorb it08:42
viricin most printers, you have to change toner + drum, right?08:42
whitequarkbtw, toner is usually polystyrene + soot08:43
whitequarkI would think toner is charged too08:43
whitequarkalthough it would not be strictly necessary (charge your hairbrush and pick up some uncharged pieces of paper with it)08:43
whitequarkapparently when you move the hairbrush near paper, it polarizes the paper, collecting the opposite charge on the side near to hairbrush, and same charge on the far side08:45
whitequarkthen, opposite charges attract, and the paper clinges to hairbrush08:45
viricthe toner has to be well produced, for humidity not to play a major role08:45
viricI remember playing with that with a balloon08:45
whitequarkas I understand it, this clinging is favorable, because it spreads the charge over higher volume => an increase in entropy08:46
whitequarkyes, toner needs to have very small particles and be very dry.08:46
whitequarkalthough, toner is very highly hydrophobic08:46
viricand I never understood how then the toner doesn't fall from the paper08:46
whitequarkvan der Waals forces08:46
whitequarkif nothing else, they'd be enough to keep it there08:47
viricif you use an eraser, you can't erase laser printed paper08:47
viricit looks like having a thin layer covering all.08:47
whitequarkah, you mean after it exits the printer? as I've said, it is melted08:47
whitequarkthe paper with attached toner is rolled through two hot cylinders, which melt the toner and force it into the pores of the paper08:48
viricthat's the part of the printer with the label "this will get very hot"?08:48
whitequarkand the reason paper exiting the printer is warm08:48
whitequarkbtw, there's a very funny story in Russian about the toner being hydrophobic08:49
whitequarkhttp://www.phantom.sannata.ru/forum/index.php?t=2616&a=do_print Ctrl+F "0 >= =5 =0<>:05B"08:49
apeletegood morning everyone08:50
apeletelarsc: I enabled dma debugging indeed, what I was wondering is "is it normal that the channels are busy ?"08:52
apeleteI thought we weren't using dma anywhere for jz4740 yet, so it seemed surprising to me that some channels were busy08:53
larscaudio uses dma08:54
larscone channel for tx, one for rx08:54
larsc-> work08:54
apeletelarsc: ok, so dma is used for audio then08:57
apeletelarsc: will do without the filter function for now if you say so, we'll talk about it later08:58
whitequarkviric: http://en.wikipedia.org/wiki/File:Laser_unit_dell_p1500_print.jpg10:33
viricwhitequark: yes, I noticed that while we talked. It has to be like a disco hall in there10:34
DocScrutinizer05you can erase toner easily with a sharp knife etc12:42
whitequarkyou can erase ballpoint pen or pencil with a sharp knife as well12:45
wpwrakyou can remove paper and whatever is on it with a sharp knife :)12:52
whitequarkyou can do everything with a sharp knife, the only limit is yourself12:54
eintopfI think you guys don't know the chinese military shovel http://www.youtube.com/watch?v=b60OZhrTB6o12:55
wpwrakoh dear13:17
wpwrakbut ... how cold they miss the potential use for kendo ?13:17
wpwrakalso, small children could use it as an umbrella13:17
wpwrakand when bagged, you should be able to play ping-pong with it13:18
wpwrakwell, or just folded13:18
eintopfwpwrak: all missed functions ;)13:21
wpwrakand regarding military use, it's kinda nice that, if you should fail to decapitate your enemies with one swift blow, you can also use it to saw through their neck :)13:21
eintopfmetal saw ;)13:22
eintopfsome of my friends bought some of them13:23
eintopffrom another friend in china13:23
wpwrakand now they're all day in the garden / woods, digging/hacking/climbing/hammering/... ? :)13:23
wpwrakah, it can be used as a frying pan, too13:25
eintopfno, but at camping ;) they dig a ditch around their tent13:25
wpwrakjust because now they can ;-)13:25
eintopfoh yes :)13:25
wpwrakah, i finally figured out what the "isoltion belt" is. it's for bush fires. to make a barrier without combustible material.13:37
eintopfwpwrak: you can also use it as paddle13:39
eintopfit's more than a swiss knife ;)13:40
wpwrakpaddle sounds smallish. they call it an "oar" ;-)   (though the video shows it being used as a paddle)13:50
DocScrutinizer05can opener looks like they're using it the wrong way. Probably better cut can into 2 halves16:08
wpwrakDocScrutinizer the destroyer :)16:56
larscwhitequark: was that you? http://www.gazeta.ru/auto/2014/01/13_a_5845877.shtml17:06
whitequarkno, but I find that hilarious17:07
larscmaybe it's a trick, say that all the speed cameras are damanged to get extra cash ;)17:11
laigualdadi am looking for some recommendations for a bluetooth usb adapter that i can use with GNU/Linux (debian), without resorting to nonfree repos. am i in the right channel?17:22
larscit's not one of the core topics, but somebody might happen to know this17:26
laigualdadok :)17:26
pcercueiBluetooth USB adapters are regular HID devices AFAIK17:39
whitequarkno, they are not, they have the USB Bluetooth class17:40
whitequarkthe radio adapters which are HID devices are somewhat more common and not bluetooth17:40
whitequarkand have the advantage that they don't need setup, or suffer from a horrible delay of several seconds on wakeup17:41
apeletelarsc: hi19:53
apeletelarsc: about dma_channel_request, should the driver request two seperate channels for rxfifo and txfifo or a single one for both rxtx ?19:55
apeletelarsc: I've seen both ways in other drivers, don't know which one to do for the mmc driver19:57
larscsince we'll never do both at the same time one should be fine19:57
apeleteinteresting, so it's not possible to read and write from mmc at the same time ?19:57
larscnot as far as I know19:59
larscyou have one data line, and it either transmits or receives19:59
apeleteright, saw that in the datasheet actually, should have paid attention20:00
apeletelarsc: ok, so I'm going to look at read_data() and write_data() now20:01
apeletelarsc: I guess a good way to handle this would be to write seperate functions to handle dma transfers and insert them in read_data and write_data, like in davinci_mmc.c20:03
nicksydneymorning / afternoon / evening lads 21:35
larscthere is a short word which means all three of them: moin21:37
whitequarkor just use UGT21:38
wpwrakthe usual greeting protocol is to omit greetings. in a world that's "always on", there is no entering or leaving.22:11
larscnicksydney seems to live outside that world22:33
nicksydneyi don't live i morphed :)22:33
wpwrakif life is change then to morph is to live23:09
DocScrutinizer05LOL @ http://security.stackexchange.com/questions/44863/phone-privacy-for-small-business23:24
wpwrakDocScrutinizer05: sounds like a future customer :)23:46
wpwrakDocScrutinizer05: and get him one of the chinese military shovels, to get rid of any nsa-provided fibers going to his data centers ;-)23:46
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