#qi-hardware IRC log for Thursday, 2014-02-06

nicksydneywpwrak: any suggestion what is a good pH, Temp sensor for aquarium ?01:02
wpwrakfish ? the direction of their bellies indicates whether the parameters would be agreeable to ... fish02:06
wpwrak(or, in other words: no idea :)02:12
nicksydneywpwrak: direction of their bellies :)....sounds like a belly dance coming up :)03:13
nicksydneywas dreaming about t-shirt with #qi-hardware on it ;)05:20
Action: DocScrutinizer05 slaps wpwrak with a K&R for not having #ifdef build-for-wpwrak in his makefiles07:51
DocScrutinizer05nicksydney: I guess any electronic pH sensor that's fish-safe is not exactly a simple and easy piece of technology07:59
DocScrutinizer05you generally don't want any physical-chemical reactions that possibly create toxin to go to the water of your aquarium08:00
DocScrutinizer05so any consuming or active process is basically ruled out08:01
DocScrutinizer05I could figure to use something like a chemical reversible pH indicator embedded into some substrate (think litmus) plus an opto-electronics to read that out08:04
DocScrutinizer05well, OR you find a set of reagents that definitely don't create any toxic products. Like CO2 and Ca for the two electrodes. I bet whitequark has a much better idea about what's possible regarding that08:08
whitequarkDocScrutinizer05: it's $7 on ebay08:11
DocScrutinizer05I dunno if some electrode materials like stainless steel plus platinium or whatever maybe create a sort of "diode" in watery acids and alkaline, just by effects of ion-to-surface adhesion or whatever08:11
whitequarkph sensor for fish08:11
whitequarkand it works by using a porous glass as a semi-permeable membrane for an electrode08:11
DocScrutinizer05whitequark: yeah, I'm sure once you found sth that works and doesn't kill your fish, it's cheap and simple to build08:12
whitequarkso, charge carriers (H+) can pass, but all other crap can not08:12
whitequarkno, I don't think you can cheaply duplicate that design, it needs glasswork08:12
whitequarkwell, that's what ph meter in our anal. chem classes was made of08:12
whitequarkand from the looks of it, the fish one is the same08:13
whitequarkI don't exactly remember how one drives a probe... I think you just pour an electrolyte inside and measure the potential08:14
DocScrutinizer05ooh - calib solution. i thought that's some consumable gue08:14
whitequarkyeah, it comes with the electrolyte even08:14
DocScrutinizer05I wouldn't like the idea to refill such probe with some obscure liquid08:15
whitequarkit's not really permeable to anything bigger than water molecules08:15
whitequarkmaybe even bigger than H+08:15
DocScrutinizer05the latter08:15
whitequarkit wouldn't work otherwise08:15
whitequarkwell, see, there's no such thing as H+08:16
whitequarkyou have a protonated H2O surrounded by a gigantic shell of like eighty more H2Os08:16
whitequarkby the way, your ideas for a ph meter were truly horrible :D08:18
DocScrutinizer05damn, I knew it: > >A solution in the reference electrode also makes contact with th esample solution and the measuring electrode through a junction,...<<08:18
whitequarkwell, first two. the third is actually pretty close08:18
DocScrutinizer05first TWO?08:19
whitequarklitmus and Ca/CO2 ones08:19
DocScrutinizer05ooh yep08:19
whitequark(makes contact) it's still through a semi-permeable membrane. the electrolyte doesn't escape that electrode as well08:20
DocScrutinizer05the second one is obvious nonsense08:20
DocScrutinizer05the first one might actually work in one way or another08:20
whitequarkwell, it's just a pain to calibrate08:20
whitequarkand reproducibly measure08:20
DocScrutinizer05I think that depends on particular build08:21
DocScrutinizer05I'd be more worried about contamination/oxidation/deterioration of the indicator08:22
DocScrutinizer05in short: long term stability08:22
whitequarkthere's also the fact that they never cover a big range08:22
whitequarkand where they do produce measurable differences (or just work at all), it's quite nonlinear08:22
whitequarkreally, no one uses ph indicators to *measure* ph. you use an indicator with a "trip point" you need, and then watch for that trip point08:23
whitequarkit's binary, not continuous08:23
DocScrutinizer05which probably is just fine for fish ;-)08:24
whitequarkthere's technically an "universal" indicator which is a mix of a lot of other indicators with different trip points08:24
whitequarkbut it kinda sucks08:24
whitequarkI dunno what fish need08:24
whitequarkcompletely no clue08:24
DocScrutinizer05know red cabbage?08:25
DocScrutinizer05which could also eb called blue cabbage08:25
DocScrutinizer05and eveb greenish, when in pH-7 range08:25
DocScrutinizer05or was it blue in pH-7 range, and green in alkaline environment?08:26
whitequarkyeah I do08:26
whitequarkit's really crude compared to modern synthetic indicators :)08:27
DocScrutinizer05seems at least trinary08:27
whitequarkwell. it really depends on what fish needs08:27
DocScrutinizer05with a rather fuzzy transition zone08:27
whitequarkif you do get into that "sweet spot" where the indicator has high delta-freq per delta-ph, good for you08:28
DocScrutinizer05yeah sure08:28
whitequarkI really was more thinking about ranges like 1-13... which is definitely not what fish needs08:28
DocScrutinizer05I'm not really good at chemical stuff08:28
whitequarkin fact it will dissolve at both ends of that range, much less breathe08:29
DocScrutinizer05dang. seems my N950 sat 2 weeks on my desk in standby, and now it started complaining than I accidentally unplugged the charger ;-)08:30
whitequarkcharging uptime counter overflow?08:30
DocScrutinizer05nah, w2 weeks of standby on one battery charge08:30
whitequarkI think win98 bsoded after at most 49 days, because a 32-bit ms count overflowed08:30
DocScrutinizer05now it started making noises due to low battery08:31
DocScrutinizer05might have been 3 weeks, I can't recall for sure when I last messed with the 7 chargers on my desk08:31
DocScrutinizer05(chemical stuff) my point been that - to test pH - you most probably need to engage into a *chemical* interaction with the substance under test. And that's *always* nasty08:33
DocScrutinizer05my 3rd suggestion been around some maybe clean physical method to probe, that doesn't involve any chemical reactions08:34
whitequarkthat ph meter from ebay isn't chemical in the sense you mean08:34
whitequarkneither electrodes nor solution inside changes during the life of electrode08:35
whitequarknot even a tiny bit08:35
DocScrutinizer05it obviously is when you need to fill it with some liquid08:35
whitequarkyou don't need to *re*fill it08:35
whitequarkit's the physical analog of the potentiometer on your DMM, a reference potential08:35
whitequarkit literally provides a reference potential08:35
DocScrutinizer05I wonder how it works then08:36
whitequarkwell. http://www.sensorland.com/Images/pH002.gif08:36
DocScrutinizer05when some substance diffuses thru the semipermeable membrane there will be some sort of "chemical" activity08:36
whitequarkfrom what I understand08:37
whitequarkactually I'm wrong here08:39
whitequarkthey do have a finite life08:39
DocScrutinizer05yeah, thought as much08:40
whitequarkok I need to sleep so badly right now08:40
DocScrutinizer05every pH probe has to work like a chemical battery basically08:40
whitequarkI'll figure it out when I'm not dropping on spot08:40
whitequarkyeah roughly08:40
DocScrutinizer05unless you make it work like a rechargable battery08:40
whitequarkI wonder what the details are08:40
DocScrutinizer05hey, your sleep periods are almost as skewed as mine 08:41
DocScrutinizer05I think you could create a "rechargeable" pH probe that 100% chemically regenerates during "charging" period08:42
DocScrutinizer05charge to 10C, the probe for 1 second, then again charge to 10C08:43
DocScrutinizer05the voltage during "discharging" should be proportional to pH08:44
DocScrutinizer05just like you can't charge a LiIon (of common chemistry) to more than 4.3V, due to the chemical system08:46
DocScrutinizer05no matter how much you overcharge it08:46
DocScrutinizer05sth like Pt-Fe or the like might actually work for that08:48
DocScrutinizer05Pt-C maybe08:48
DocScrutinizer05maybe even Au-C08:48
DocScrutinizer05H+ may get "adsorbed" by one of the material surfaces, the more pH the more voltage08:50
DocScrutinizer05"charging" should "clean" both electrodes again08:50
DocScrutinizer05as long as your charging voltage is < electrolytic voltage of H2O, nothing bad shall happen. Of course this voltage has to suffice to completely "charge" the system08:52
DocScrutinizer05so the electrochemical distance between the two electrode materials shall be < H2O electrolytic voltage08:53
DocScrutinizer05I shpould shut up, chemistry is my weak spot08:53
DocScrutinizer05just suffices for a thorough fascination for violent redox reactions and spontaneous decay of unstable molecules08:55
DocScrutinizer05the latter ones particularly funny, I always tend to think of house made of cards08:56
DocScrutinizer05reading http://www.sensorland.com/HowPage037.html I recall the awesome electron tube powered voltmeter I had in the 70s. IIRC it had an input impedance of 100G-Ohm/V09:28
DocScrutinizer05you're literally entering a whole new world of physical effects with such a device09:28
DocScrutinizer05probe the electrostatic charge of plastic objects, discover photovoltaic effects where you never expected them, etc09:29
wpwrakwhitequark + endmills = joy ;-)13:40
whitequarkokay, it broke in about 20 seconds.22:01
larscalways happens the first time22:01
nicksydneywpwrak: http://www.ebay.com/itm/28123766371122:15
nicksydneyDocScrutinizer05: thanks for the explanation 22:27
nicksydneyhttps://makeplaylive.com/#/home seems like the arm-netbook community has launch it22:38
paul_boddienicksydney: Did you link to the DragonBox Pyra or was that someone else? http://www.pyra-handheld.com/22:58
nicksydneysomeone else 22:58
nicksydneynever seen that one before ..thanks22:58
paul_boddieIt's the OpenPandora successor, although the open doesn't refer to the hardware.22:59
nicksydneyyeah ... noticed in the team Dr. Nikolaus Schaller...very nice !22:59
paul_boddieI hope that on this one Nikolaus will get them to open the designs or something.22:59
paul_boddieMaybe I heard about it via the GTA04/Neo900 channels.23:00
nicksydneymaybe DocScrutinizer05 know something about this ?23:00
nicksydneyyikes! the tech specs is mad ! 2x ARM Cortex-A15 @ 1.7Ghz with NEON SIMD....YUMMY !23:01
nicksydneyusing Texas Instruments OMAP 5 SoC23:01
paul_boddieThe blog post about shopping around for SoCs is informative: http://boards.openpandora.org/topic/15560-soc-back-and-forth/23:06
paul_boddieA good reminder of why the open hardware movement needs to reach the SoC level.23:06
nicksydneypaul_boddie: thanks...a very good read indeed..especially for someone like me who are new and still learning :)23:16
paul_boddieI think you're more of an expert than you think now. Way beyond my level, at least in terms of willingness to get your hands dirty. :-)23:19
paul_boddieAnd as for all this ARM stuff, my ARM activities largely fell away long before it became popular and cool.23:20
paul_boddieBut I think I'll go retro for a bit just for the fun of it. Maybe even fire up the emulators again. :-)23:21
nicksydneypaul_boddie: never too late to learn anything...just trying as much as possible to absorb so much information that i can read ...boy i think if my brain can talk it will say "STOP! you are hurting me :) " .. heheh23:22
paul_boddieIt really is a golden age for tinkering, that's for sure.23:23
nicksydneyyeah it is...never expect the day will come for us engineers :)23:25
nicksydneyor artists for that matter :)23:25
nicksydneythis is another cool thing happening now https://devart.withgoogle.com/23:27
DocScrutinizer05I have no idea about openpandora / pyra23:42
DocScrutinizer05and nikolaus is not that much a fan of open hardware actually, to push the pandora team towards anything like that. My notion at least23:43
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