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smaerd
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Mood: hmm...
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That's a really creative solution m1tanker. I guess what I am confused about is this. A speaker is in effect, a solenoid? Why fuss around working
indirectly with a solenoid. Sure speakers are cheaper(unless you wrap the solenoid yourself) but if you have to buy an amplifier, tune circuitry, and
write soft-ware to correct for a lot of the 'speaker induced issues' why not choose a solenoid directly?
I would be afraid that there would be some lateral or longitudinal oscillations added from a speaker, I have no real evidence to suggest that would
happen but I don't think of speaker heads as firm things.
The real question is, how far of a throw do you need SupaVillain? Then an actual mechanism can be thought up.
The idea about using one of those harbor freight digital calipers is a great one, if it provides the resolution necessary. If I finish all the
projects I'm working on and no one has done it yet, maybe I'll crunch some numbers for the interferometer specifications... That'd probably be in a
few weeks though.
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smaerd
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Supavillain, I don't want to sound disenchanting but, yes ATR attachments are simple in an optical diagram. Constructing one is an entirely different
story. Not that they are super complicated things, but I've been surprised by the difficulty of turning pen and paper into reality with even 'simple'
projects. Aligning optics and everything else... Also ATR crystals do not have to be diamond at all. Most of the reasonably priced ones are ZnSe iirc.
I'd like to see more about this fringe analysis stuff. Do you have any links?
I recently found one of these researching another users posts. Super interesting, depending on detector costs, might be the way to go.
http://www.pyreos.com/products/handheld-mid-ir-spectrometer....
http://www.azom.com/article.aspx?ArticleID=9726
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m1tanker78
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True. A glorified solenoid with a cone attached to it (sort of)
Quote: Originally posted by smaerd  | | I would be afraid that there would be some lateral or longitudinal oscillations added from a speaker, I have no real evidence to suggest that would
happen but I don't think of speaker heads as firm things. |
That's a valid point.
A solenoid usually is happy if it's either fully on or fully off. In between becomes somewhat undefined and therefore, clunky.
A typical speaker has a sleeve that rides on a core. Usually the sleeve and core are manufactured to a pretty tight tolerance (not perfect but
surprisingly tight). A typical speaker also has a stabilizing baffle (sorry, I forget what they're really called) at the rim to which the cone is
attached.
The result is if you gently press down on one side of the cone, generally speaking the whole cone moves down pretty uniformly rather than badly
skewing.
| Quote: Originally posted by smaerd | | The real question is, how far of a throw do you need SupaVillain? Then an actual mechanism can be thought up. |
I'm not sure he even knows. IR occupies a huge chunk of EM spectrum. Best case would be 1mm. Worst case would be ~700nm (0.0007mm!!). I would have
jumped on this project if CaF optics weren't so damned expensive.
Could someone explain the detector part of the interferometer? If IR intensity is being measured in the time domain then run through a Fourier
Transform to obtain the frequency domain representation, why not use an inexpensive detector? Is it because the cheap detector's window won't pass all
the frequencies in the IR range?
Tank
Chemical CURIOSITY KILLED THE CATalyst.
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smaerd
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I'm far from knowledgeable about FT-IR detectors but I do know that the window is important for the over-all range that can be observed
(transmission).
I have also heard DLaTGS (Deuterated Alanine Doped Triglycine Sulphate) detectors are the bee's knee's when it comes to mid-IR pyroelectric detectors
- http://www.microwattonline.com/images/files/MWA5000.pdf
http://infrared.als.lbl.gov/content/equipment/49-detectors/8... (KBr window)
I think a lot of it really has to do with sensitivity and the semiconductor material they are made out of (cost-wise). I'm not sure by what you mean
by an inexpensive detector. I'd like to learn more about suitable detectors in general so if you have any examples I'd like to see. Some of them have
built in temperature regulation and things like that which would be really nice (if not critical).
I'm having a hard time even finding pricing on these kinds of detectors. Little worried they aren't off the shelf type components. Anyone have any
information to the contrary? I bet there's something out there off the shelf with a low cost that could be used for FT-IR though, even if it required
popping a little KBr disc over it.
I see what you mean about the speaker now, that is a cool idea. Might not need too much of an amplifier if the throw is small. Could probably even
build a simple amp circuit.
Edit - Sorry forgot to lower-case a letter in the DLaTGS thing and I know someone out there would write a snippy post about it.
[Edited on 10-12-2014 by smaerd]
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SupaVillain
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Yea i honestly dont really know yet, how far the displacement is, however, those DLaTGS detectors would be amazing but i cant "deuterize" things or
find deuterium for sale or anything like that. No idea of any of that stuff. Im going for this "eltec model 420-0" lithium tantalate pyroelectric
detector at http://silverlight.ch/laser.php and with no window it somehow has full spectrum optical bandwidth.
I would think were using more expensive detectors because of the resolution of the spectrum, also those HgCdTe detectors are hard to make lol. I coul
make my own cheap litium tantalate detector but i dont know enough about the little mechanisms of the electronic components in it, like the FET, FET
gate, the capacitor setup, im lost on that and i dont want to "wing" the cutting of a crystal and hope i do it perfectly flat.
As far as tracking the thingy with fringes i have been lucky enough to locate the aerial view picture of the exact same FTIR as in the video i posted
of the teardown, this picture here, http://www.umich.edu/~orgolab/ir/pic/ftir.jpg , shows you a LOT of useful information. Im talking about the laser path!
The laser fringe sensor is purely and widely CCD stuff and sometimes photodiode array but im just gonna go with CCD. Google "CCD arduino spectrometer"
and theres a lot of projects posted about, of course nothing at this level of quality and expense of a project, but it's nice to see how theyre hooked
up and respond to light.
Oh and it turns out, the OMNIC software has to be paid for, but as it also turns out, "openfringe" isnt just for analysis of fringes and can take the
interferogram and do all the FFT analysis as well. However i do not think it has a library and im still looking for sonething about that, if i have to
i could download all the pictures of spectrums from a source like sigma aldrich or those chemical info web sites that just happen to have FTIR
spectrum data available, and then place them in an image search engine, for example I'd have the spectrum at hand entered in the search field and it
would choose the closest matches in there. To see this work, go try to use google image search, however this would be an offline library for myself.
Thinking of using the pendulum periscope idea for the moving mirror as well.
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SupaVillain
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Well if youre looking to build your own FTIR i think this thread covers all the info you need, otherwise you need to do more research. Not gonna
summarize this
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Texium
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Thread Moved
22-11-2023 at 19:04 |
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