[HN Gopher] A DIY near-IR spectrometer
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A DIY near-IR spectrometer
Author : johnmaguire
Score : 261 points
Date : 2023-09-13 15:33 UTC (7 hours ago)
(HTM) web link (caoyuan.scripts.mit.edu)
(TXT) w3m dump (caoyuan.scripts.mit.edu)
| ckocagil wrote:
| Nice project. A low DA capacitor Cf in parallel with the gain
| setting resistor Rf can average out more noise if needed. It can
| even deal with the mains noise if that remains an issue. Another
| potential improvement: addition of an optical chopper wheel to
| deal with the entire system's 1/f noise. The downside is this
| would require higher sampling rate which would then get
| demodulated + filtered externally. Would also limit Cf to higher
| frequencies.
| lawlessone wrote:
| Between this and the DIY radio telescopes and wifi radar, maybe
| we will have a real tricorder some day.
| 0xdeadbeefbabe wrote:
| hehe no mention of the new iphone 15
| JKCalhoun wrote:
| I'm just happy with all these "Amateur Scientist" links lately.
| More of these!
| oceanplexian wrote:
| I wonder if this could be used for amateur astronomy? Would be
| cool to point a telescope at a star, and print out a spectrum
| corresponding to elements with emission lines.
| jacquesm wrote:
| For that a prism and a photographic film would probably be
| sufficient, the developed film would serve as your print-out.
| oscord wrote:
| [flagged]
| fanick wrote:
| Similar project with single photo diode enclosed in sort of a
| pinhole camera: https://hackaday.com/2016/05/18/using-missile-
| tech-to-see-li...
| pimlottc wrote:
| To save time waiting for the content to animate in:
| javascript:document.querySelectorAll(".animate-box").forEach(e =>
| { e.classList.remove('animate-box') })
| progbits wrote:
| This is very nice, but most of that $10k probably pays for
| certification that you won't get for DIY. Great for hobbyist, but
| you couldn't sell it for $9500 profit.
| ortusdux wrote:
| I wonder what 3rd party certification would cost. Industries
| that use sensors like this frequently require annual
| recertification, so there are typically multiple testing houses
| and competitive prices.
| jacquesm wrote:
| There is a huge difference between _calibration_ and
| _certification_. Calibration means that your instrument gives
| you absolute rather than relative output. Certification means
| that your instrument is precise enough to be used for
| specific procedures.
|
| Calibration can be done in house, certification is usually
| the domain of some certification institution and can be
| extremely expensive depending on the kind of gear.
| jacquesm wrote:
| So what? If you need it, now you can build it. As a hobbyist
| you don't need certified gear, you need gear.
| MrBuddyCasino wrote:
| The point wasn't "you can get rich selling this", but "you can
| save $$$ building this yourself as a hobbyist".
| progbits wrote:
| Absolutely, you are correct.
| CamperBob2 wrote:
| If you're using it in a lab, you can calibrate and verify this
| sort of instrument yourself most of the time. Wavelength is
| trivial to calibrate. Absolute amplitude not so much, but you
| usually don't care that much about absolute amplitude. Response
| flatness across the spectrum may or may not be a concern.
| [deleted]
| w10-1 wrote:
| DIY is not just for hobbyists.
|
| Companies face the build-or-buy question every day. This
| article demonstrates that you can build and validate your build
| with the knowledge and skills expected of most principal
| investigators. If I were a lab director, I would want my people
| to be able to consider building when it makes sense,
| particularly since we can then integrate systems and tailor
| validation to our requirements.
|
| That's the stuff of proprietary IP and career advancement.
| version_five wrote:
| My first thought as well. People tend to misunderstand why
| things cost what they do, for stuff like this it isn't the raw
| components.
| MostlyStable wrote:
| Possibly, but he also describes pretty cheap and easy
| calibration methods. It's possible that most of the cost of the
| commercial options is the fact that these are extremely low-
| volume devices and the overhead of a business with low-volume
| sales is quite high. You might be paying less for calibration
| and more for all the things a business needs to do/have that a
| lone DIYer doesn't.
|
| Not to mention the fact that a lot of researchers are buying
| thing with grant money, and so can be, in some cases, somewhat
| price insensitive.
|
| I don't doubt that the commercial one is pre-calibrated and
| certified. But I would be quite surprised if that
| certification/calibration _actually_ cost ~$9000.
| progbits wrote:
| Sure I'm not saying that. If you give away the R&D for free
| and don't seek profit you can build it much cheaper.
|
| But self-calibrating is still something else. Unless I pay
| some lab with traceable calibration to do it for me I can't
| use the results to certify other equipment for example. I
| think it's more like insurance, sure the unit cost is low but
| you pay extra so in case the lab screws up they pay for the
| mess.
| MostlyStable wrote:
| That's fair, but I think a lot of people other than "DIY
| hobbyists" don't have a need for traceable, liability
| responsible, validation chains.
| s0rce wrote:
| I'm not sure about certification but there is a lot of overhead
| in designing, producing, selling and servicing products. This
| is basically a prototype. It will probably work for a while but
| will be difficult to maintain if something goes wrong and the
| software won't be very polished. There are a lot of non-BOM
| costs that go into selling a commercial spectrometer. This is
| great if you want to DIY one but even a single sensor based
| visible light spectrometer with cheap parts can't be bought for
| close to the sum of its parts.
| client4 wrote:
| A different design could leverage laser micro ablations on glass
| over a traditional CMOS sensor.
| herf wrote:
| I think this design is usually called a "scanning monochromator"
| - really nicely done.
| gaze wrote:
| This write-up and project is from the same guy that discovered
| superconductivity in bilayer twisted graphene. Pretty impressive.
| SaulJLH wrote:
| Aside from pure curiosity and or research purposes... Is there
| any everyday/practical apps/uses for something like this, for
| the avg joe? Building something for 500 that would normally be
| 10k, already has me intruiged.
| thatcat wrote:
| You could run Quality Control on your amazon chemical
| purchases if you were willing to put in time to find methods
| using spectrophotometery in this wavelength range.
| nielsole wrote:
| I don't know how uncommon that is, but more than 14k citations
| at age 25, most of which as first author sounds pretty darn
| impressive.
| [deleted]
| darkclouds wrote:
| Not knocking his efforts, but I guess its on a par to writing
| some code or making something which is used by many people.
| gaze wrote:
| It really isn't -- unless you're talking something like
| bzip2 or some extremely nontrivial thing.
| barelyauser wrote:
| I once went through quite an experience. Used to work with
| a guy that was awarded a big prize in his field. I think
| one day he got tired of being treated as "some kind of
| genius", as he said. He started to discuss a topic one day,
| listening to my answers and questions back and forth. At
| the end the discussion hit a point where we could not go
| further. He then told me: "if you then submitted this as a
| proposal, were lucky enough to have it granted and just
| answered the last question you asked me with a simple
| experiment, you would receive the same prize as I did".
|
| That guy was great.
| heyoni wrote:
| And a genius lol. Don't tell him I said that
| zeagle wrote:
| Probably underestimates it. Not my field, I don't know of
| this guy but a few hundred citations is you write a library
| that everyone uses and similar academic recognition and
| academic platinum for tenure on the background of other
| publications. 300 000 is the equivalent of writing the
| Linux kernel or sqlite.
|
| https://www.nature.com/news/the-top-100-papers-1.16224
| etrautmann wrote:
| Right - that's impressive
| 0xbadcafebee wrote:
| Articles like these are rare, but there's 30 years of them
| scattered around the internet. There's got to be a way to
| catalogue them in a single index somewhere. Like a Wiki, but just
| articles that are hard to find and extremely interesting.
|
| I'd like an index because HN's articles are often not this
| caliber of "interesting". If I look back 1 month to the top of HN
| (https://news.ycombinator.com/front?day=2023-08-12), there's
| pontifi-posting (editorials), news and editorials from large
| media companies, blogspam from tech companies and OSS projects,
| and basic tech How Tos. I don't want to read any of that; I come
| back hoping there's a single one of this kind of article, and
| maybe find one a month.
| EricMausler wrote:
| Sounds like you want a curated feed. There are some email
| mailing lists that aim to achieve this, usually for a specific
| domain (like stock market, or AI, etc)
|
| Maybe a group chat or discord of like minded people who
| casually share things they come across that pass a high
| standard
|
| One way or another it seems like you're going to need to rely
| on another person to sift through all the daily published
| content and mark potentially interesting ones
| MayeulC wrote:
| I wonder if you could just feed HN titles with more than ~30
| upvotes to an LLM and ask it to bring out similar topics. Not
| perfect, but I think it could work as a start.
| mdip wrote:
| I have to agree with you. While I do enjoy the OSS
| projects/physics-/math-related topics (and a lot of the Show
| HN), these are my absolute favorite things to read.
|
| Curious if you've found other resources that provide more of
| this sort of content?
|
| I've found the Hackaday blog[0] tends to have a lot of this
| kind of content (often summarized/linked to the original
| source) and _sometimes_ it 's tagged in a way that makes
| surfacing others from their archives possible, but I've not
| found any other sites that are reasonably organized to help
| surface write-ups of this kind[1].
|
| [0] https://hackaday.com/blog
|
| [1] There are subreddits where this sort of thing can be found,
| but "deep-dive but accessible technical articles" tend to be
| placed in a sub-reddit that's dedicated to more narrow topics
| and a lot are lower quality (there's similar content to this in
| /r/Optics from 2022, but I'd never have a reason to end up
| there)
| walterbell wrote:
| Manually curated list could be crowdsourced via an OSS project,
| e.g. 1. Criteria for articles in list. 2.
| Example and anti-example articles. 3. Tag via HN comment
| with short, unique and human-meaningful phrase. 4. Query
| Algolia periodically, triage, PR submission/review/merge.
| 5. Syndicate list as RSS feed.
| [deleted]
| rolph wrote:
| >>While a silicon-based camera is as cheap as dirt these days, an
| one-dimensional InGaAs pixel array already costs upper few
| thousand dollars. Any full-blown IR spectrometer system goes way
| over $10k, with their fancy thermoelectric cooling and precision
| gratings (we actually have one in our lab). The reason why they
| are so expensive is that the target user group are scientific
| researchers, not consumers. <<
|
| the expense is a product of intended use. performance guarantee,
| is responsibility for design failure. scientific instrumentation
| must be very consistent for the purpose.
| SV_BubbleTime wrote:
| Yea ok but...
|
| Certain things just need an answer quickly. Like, some science
| that you do in order to do other science. And you can't get
| there without a $10,000 device, you can't even get started with
| some other experiment.
|
| There isn't anyone making hobbiest optical sensors. I looked
| for a project I needed a laser for. My options were, don't do
| it, or pay $4000 for a late 80s sensor I needed off eBay then
| try and figure out how the thing worked with no software and a
| proprietary cable. Sound like fun? Not to me. And I didn't have
| $10k for the USB version from the early 2000s, again with no
| software. And obviously far from thr $50k for a UBS3 new model.
|
| Optical equipment is stupid expensive and sometimes you just
| need "basic tools" for advanced things.
| jamal-kumar wrote:
| Wow this is the coolest thing. I was looking at trying to build a
| DIY raman spectroscope and you can make one of those for under
| 100$ [1], but near-IR spectroscopy opens up more possibilities
| for sure. From what I understand (I'm not a scientist but I love
| the idea of having access to these tools) raman spectrscopy is
| limited to asymmetric crystalline molecules, so you can't really
| get a good reflection off of say salt to get a reading. (Edit -
| Looks like Near-IR is complimentary - "Raman active vibrations
| aren't visible in the infrared for molecules with a symmetrical
| stretch. Similarly, infrared active vibrations aren't visible in
| the Raman spectra for molecules with asymmetric stretch. This is
| known as the Principle of Mutual Exclusion and is what makes NIR
| and Raman Spectroscopy complementary techniques." [2] ) What
| we're really hoping to find out is if we can detect stuff like
| pthalates in plastics and heavy metals such as cadmium in metal
| products, I understand we'll probably just want to send things
| off to a lab to get GC/MS done for those things after talking to
| some people who have more experience than I do but I still want
| to see if I can build a bunch of these raman or near-IR
| spectroscopes for pharmacies in the third world. Counterfeit
| drugs are a real problem out there and they don't need to be.
|
| [1]
| https://www.hackteria.org/wiki/images/a/a0/MobPhone_RamanSpe...
|
| [2] https://www.labmate-online.com/news/mass-spectrometry-and-
| sp...
| z3phyr wrote:
| Maybe we should have more fundamental science collectives where
| amateurs can also contribute, in addition to academic and state
| funded institutions. Sort of like amateur astronomy clubs
| [Amateur astronomers still contribute widely to their field(s)],
| in larger scale and contributing in much more significant ways.
|
| Yes to more amateur scientist articles on HN!
| [deleted]
| KRAKRISMOTT wrote:
| The author's clearly not an amateur. He's a condensed matter
| postdoc.
| swores wrote:
| I think there's an argument to say that he was doing it as
| part of his work, but I'll make this point anyway: if he was
| doing it for fun and to entertain people in a way unrelated
| to his actual job, wouldn't it still be "amateur science"?
| The same way that if a premier league footballer or an MLB
| hall of famer went with their family to play a game in the
| park, that's amateur football/baseball despite being done by
| a professional.
|
| And while one could argue that the words used were "amateur
| scientist" rather than "amateur science", it could also be
| argued the opposite direction by suggesting that tag might
| not actually apply to the author but instead to the type of
| content since it's to be read and perhaps replicated by
| amateur scientists more than professional ones.
|
| Or we could just celebrate the article regardless of the
| accuracy of someone's throwaway remark's categorisation of it
| :p
| bkloppenborg wrote:
| As you mentioned, astronomy is a field where contributions by
| amateurs / citizen scientists are extremely valuable. A few
| organizations that exemplify this are: (1) the American
| Association of Variable Star Astronomers (disclaimer, I'm their
| Executive Director) which collects photometric (brightness)
| data as well as spectroscopic data on variable stars and
| kindred objects including exoplanets (2) the Society for
| Astronomical Sciences which is more broad than AAVSO, but with
| a moderate focus on instrumentation (3) the Center for Backyard
| Astrophsyics (hyper specialized on one type of variable star, a
| good collaborator of the AAVSO) (4) the International
| Occultation and Timing Association that observe asteroids
| occulting (blocking) stars to infer their shapes
|
| Most countries have organizations similar to these too.
|
| Edit: There is a group within the SAS working on an automated
| optical spectrograph for astronomy called the FlexSpec 1
| (https://flexspec1.readthedocs.io/en/latest/). It is about $500
| in parts. Similar devices sell for about $3,000.
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