<nicksydney>
wpwrak: any suggestion what is a good pH, Temp sensor for aquarium ?
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<wpwrak>
fish ? the direction of their bellies indicates whether the parameters would be agreeable to ... fish
<wpwrak>
(or, in other words: no idea :)
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<nicksydney>
wpwrak: direction of their bellies :)....sounds like a belly dance coming up :)
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<nicksydney>
was dreaming about t-shirt with #qi-hardware on it ;)
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* DocScrutinizer05
slaps wpwrak with a K&R for not having #ifdef build-for-wpwrak in his makefiles
<DocScrutinizer05>
nicksydney: I guess any electronic pH sensor that's fish-safe is not exactly a simple and easy piece of technology
<DocScrutinizer05>
you generally don't want any physical-chemical reactions that possibly create toxin to go to the water of your aquarium
<DocScrutinizer05>
so any consuming or active process is basically ruled out
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<DocScrutinizer05>
I could figure to use something like a chemical reversible pH indicator embedded into some substrate (think litmus) plus an opto-electronics to read that out
<DocScrutinizer05>
well, 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 that
<whitequark>
DocScrutinizer05: it's $7 on ebay
<DocScrutinizer05>
I 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 whatever
<whitequark>
ph sensor for fish
<whitequark>
and it works by using a porous glass as a semi-permeable membrane for an electrode
<DocScrutinizer05>
whitequark: yeah, I'm sure once you found sth that works and doesn't kill your fish, it's cheap and simple to build
<whitequark>
so, charge carriers (H+) can pass, but all other crap can not
<whitequark>
no, I don't think you can cheaply duplicate that design, it needs glasswork
<DocScrutinizer05>
nifty
<whitequark>
well, that's what ph meter in our anal. chem classes was made of
<whitequark>
and from the looks of it, the fish one is the same
<whitequark>
by the way, your ideas for a ph meter were truly horrible :D
<DocScrutinizer05>
damn, I knew it: > >A solution in the reference electrode also makes contact with th esample solution and the measuring electrode through a junction,...<<
<whitequark>
well, first two. the third is actually pretty close
<DocScrutinizer05>
first TWO?
<whitequark>
litmus and Ca/CO2 ones
<DocScrutinizer05>
ooh yep
<whitequark>
(makes contact) it's still through a semi-permeable membrane. the electrolyte doesn't escape that electrode as well
<DocScrutinizer05>
the second one is obvious nonsense
<DocScrutinizer05>
the first one might actually work in one way or another
<whitequark>
well, it's just a pain to calibrate
<whitequark>
and reproducibly measure
<DocScrutinizer05>
I think that depends on particular build
<DocScrutinizer05>
I'd be more worried about contamination/oxidation/deterioration of the indicator
<DocScrutinizer05>
in short: long term stability
<whitequark>
there's also the fact that they never cover a big range
<whitequark>
and where they do produce measurable differences (or just work at all), it's quite nonlinear
<whitequark>
really, no one uses ph indicators to *measure* ph. you use an indicator with a "trip point" you need, and then watch for that trip point
<whitequark>
it's binary, not continuous
<DocScrutinizer05>
which probably is just fine for fish ;-)
<whitequark>
there's technically an "universal" indicator which is a mix of a lot of other indicators with different trip points
<whitequark>
but it kinda sucks
<whitequark>
I dunno what fish need
<whitequark>
completely no clue
<DocScrutinizer05>
know red cabbage?
<DocScrutinizer05>
which could also eb called blue cabbage
<DocScrutinizer05>
and eveb greenish, when in pH-7 range
<DocScrutinizer05>
or was it blue in pH-7 range, and green in alkaline environment?
<whitequark>
yeah I do
<whitequark>
it's really crude compared to modern synthetic indicators :)
<DocScrutinizer05>
seems at least trinary
<whitequark>
well. it really depends on what fish needs
<DocScrutinizer05>
with a rather fuzzy transition zone
<whitequark>
if you do get into that "sweet spot" where the indicator has high delta-freq per delta-ph, good for you
<DocScrutinizer05>
yeah sure
<whitequark>
I really was more thinking about ranges like 1-13... which is definitely not what fish needs
<DocScrutinizer05>
I'm not really good at chemical stuff
<whitequark>
in fact it will dissolve at both ends of that range, much less breathe
<DocScrutinizer05>
dang. seems my N950 sat 2 weeks on my desk in standby, and now it started complaining than I accidentally unplugged the charger ;-)
<DocScrutinizer05>
.s/than/that/
<whitequark>
charging uptime counter overflow?
<DocScrutinizer05>
nah, w2 weeks of standby on one battery charge
<whitequark>
I think win98 bsoded after at most 49 days, because a 32-bit ms count overflowed
<DocScrutinizer05>
now it started making noises due to low battery
<DocScrutinizer05>
might have been 3 weeks, I can't recall for sure when I last messed with the 7 chargers on my desk
<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* nasty
<DocScrutinizer05>
my 3rd suggestion been around some maybe clean physical method to probe, that doesn't involve any chemical reactions
<whitequark>
that ph meter from ebay isn't chemical in the sense you mean
<whitequark>
neither electrodes nor solution inside changes during the life of electrode
<whitequark>
not even a tiny bit
<DocScrutinizer05>
it obviously is when you need to fill it with some liquid
<whitequark>
you don't need to *re*fill it
<whitequark>
it's the physical analog of the potentiometer on your DMM, a reference potential
<whitequark>
it literally provides a reference potential
<DocScrutinizer05>
when some substance diffuses thru the semipermeable membrane there will be some sort of "chemical" activity
<whitequark>
from what I understand
<whitequark>
actually I'm wrong here
<whitequark>
they do have a finite life
<DocScrutinizer05>
yeah, thought as much
<whitequark>
ok I need to sleep so badly right now
<DocScrutinizer05>
every pH probe has to work like a chemical battery basically
<whitequark>
I'll figure it out when I'm not dropping on spot
<whitequark>
yeah roughly
<DocScrutinizer05>
unless you make it work like a rechargable battery
<whitequark>
I wonder what the details are
<DocScrutinizer05>
hey, your sleep periods are almost as skewed as mine
<whitequark>
word
<DocScrutinizer05>
I think you could create a "rechargeable" pH probe that 100% chemically regenerates during "charging" period
<DocScrutinizer05>
charge to 10C, the probe for 1 second, then again charge to 10C
<DocScrutinizer05>
then*
<DocScrutinizer05>
the voltage during "discharging" should be proportional to pH
<DocScrutinizer05>
just like you can't charge a LiIon (of common chemistry) to more than 4.3V, due to the chemical system
<DocScrutinizer05>
no matter how much you overcharge it
<DocScrutinizer05>
sth like Pt-Fe or the like might actually work for that
<DocScrutinizer05>
Pt-C maybe
<DocScrutinizer05>
maybe even Au-C
<DocScrutinizer05>
H+ may get "adsorbed" by one of the material surfaces, the more pH the more voltage
<DocScrutinizer05>
"charging" should "clean" both electrodes again
<DocScrutinizer05>
as 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 system
<DocScrutinizer05>
so the electrochemical distance between the two electrode materials shall be < H2O electrolytic voltage
<DocScrutinizer05>
I shpould shut up, chemistry is my weak spot
<DocScrutinizer05>
just suffices for a thorough fascination for violent redox reactions and spontaneous decay of unstable molecules
<DocScrutinizer05>
the latter ones particularly funny, I always tend to think of house made of cards
<DocScrutinizer05>
reading 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/V
<DocScrutinizer05>
you're literally entering a whole new world of physical effects with such a device
<DocScrutinizer05>
probe the electrostatic charge of plastic objects, discover photovoltaic effects where you never expected them, etc
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<whitequark>
ENDMILLS
<wpwrak>
whitequark + endmills = joy ;-)
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<paul_boddie>
A good reminder of why the open hardware movement needs to reach the SoC level.
<nicksydney>
paul_boddie: thanks...a very good read indeed..especially for someone like me who are new and still learning :)
<paul_boddie>
I 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. :-)
<paul_boddie>
And as for all this ARM stuff, my ARM activities largely fell away long before it became popular and cool.
<paul_boddie>
But I think I'll go retro for a bit just for the fun of it. Maybe even fire up the emulators again. :-)
<nicksydney>
paul_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 :) " .. heheh
<paul_boddie>
It really is a golden age for tinkering, that's for sure.
<nicksydney>
yeah it is...never expect the day will come for us engineers :)
<DocScrutinizer05>
I have no idea about openpandora / pyra
<DocScrutinizer05>
and nikolaus is not that much a fan of open hardware actually, to push the pandora team towards anything like that. My notion at least