Optical Building a Raman spectrometer….

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Arduino technology has advanced to a point where it could potentially serve as a more practical alternative for on-the-spot drug purity testing compared to previous Raspberry Pi mass spectrometry projects, which were cumbersome and not mobile. The goal is to create a compact device that can recognize various drugs and their purity, with a focus on saving lives. There is a discussion about the differences between Raman and mass spectroscopy, clarifying that they are distinct techniques requiring different hardware. The conversation also highlights the importance of building a reliable database of real drugs for accurate identification. Overall, the community is exploring the feasibility of using Arduino sensors for this purpose.
  • #31
sbrothy said:
Your wife has no comments on that? :woot:
She mainly knows about the fire at home (at our old apartment years ago), and we laugh about it now. It involved a HAM radio project (we are both HAMs), where I made a fundamental mistake in building a large battery backup box. That was embarrassing...
 
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  • #32
berkeman said:
She mainly knows about the fire at home (at our old apartment years ago), and we laugh about it now. It involved a HAM radio project (we are both HAMs), where I made a fundamental mistake in building a large battery backup box. That was embarrassing...
Eeesh! :smile:
 
  • #33
The original paper (including the "Supporting Information") is a little silent on the nature of the lenses. I'd like to analyze my beam using a laser beam profiler but that darn thing is even more expensive than the spectrometer itself. I could build it myself but where will I end up having to build gizmo after gizmo?

I hope I understand that the long pass filter is supposed to filter out the Rayleigh radiation and as such is a pretty straightforward acqusition. The lenses om the other hand....

I've come to understand that I need biconvex lenses as the beam has to go back and forth through it. but their exact nature still eludes me a little. Can I just "try" with what I think are the proper ones, or do I need to profile the beam and "math it out"? The example I'm trying to follow uses a cube beam splitter (splitting the beam 70%/30%) but I'm wondering whether it wouldn't be smarter using a "proper" beam splitter?

Incidentally, I found this, related, document:

The Design and Construction of an Affordable Raman Spectrometer.
 
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  • #34
Well, actually doing my homework myself and understanding the difference between "cut-off" and "cut-on" filters I realize I need a "cut-off" filter blocking wavelengths longer than 550nm in order to cut off Rayleigh scattering radiation.

I'm surprised about the prices of these lenses though! Cheap they aren't! I read somewhere one can use ordinary magnifying glasses instead of biconvex lenses, but I doubt that works for laser light though.
 
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  • #35
  • #37
sbrothy said:
OK, after using my own brain and search skills I think I found the correct long-pass filter (no affiliation of course):

https://www.thorlabs.com/thorProduct.cfm?partNumber=FGL550S

Although I think I need an uncolored one.

and the lenses:

https://www.thorlabs.com/search/thorsearch.cfm?search=biconvex+lens+laser

Just need to find out which coating I need, if any.

I must admit I'm surprised that the filter and lenses are the most expensive part of this project!

Well, it turns out I “need” the colored one after all. At least that’s what they use in the paper I’m using as a guide.

Again, I’m in no way affiliated with Thorlabs. They just seem to have most of what I need, albeit, as I mentioned, they have no scruples charging you. In fact, they also have a complete Raman Spectrometer Kit.

Again, cheap it is not.
 
  • #38
I bought My engineer partner in this bought this SparkFun Triad Spectroscopy Sensor - AS7265x (Qwiic) but I think this was a mistake (and the blame for this is mine as he did it on my request). It can do 3 different types of spectroscopy, but none of them is really what I need. It may turn out to be useful anyway though.

Details here:

https://mm.digikey.com/Volume0/opasdata/d220001/medias/docus/697/SEN-15050_Web.pdf

EDIT: Fun fact: as dimensions are difficult to assess I thought it was 10x10 cm, but it turned out to be 2x2 cm!

82829E37-3A3D-474E-8139-B9E1BA785CD9.webp
 
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  • #39
I bragged about not going down on equipment and then I stumbled across this guy’s blog.

I must admit I feel like I’m missing something here now.

Also, just ftr I should mention that my engineer partner bought the triad board (on my wrong request). I better find something constructive to use it for now! :smile:
 
  • #40
A DIY spectrometer for harm reduction is an incredible, life-saving goal. The biggest challenge will be ensuring clean, reproducible spectra from that weak Raman scattering. Good luck overcoming the technical hurdles. I'll be following your updates!
 
  • #41
Thank you for the kind words. As you say it's gonna be an uphill battle.

EDIT: I know this is inanely weak but I couldn't resist: It's gonna be like the attack of the laser light brigade. (I'm really sorry!)

Almost incidentally, it occurs to me that the SparkFun Triad Spectroscopy Sensor - AS7265x (Qwiic) could perhaps be used to build a makeshift pulse oximeter measuring the SpO2 of someone under the influence of drugs reducing the oxygen intake.

They're probably not voluntarily gonna make me measure it, and if they already have blue lips the SpO2 probably isn't the most important variable. It's in the scenario ballpark though and it's something productive to use the board for! :woot:
 
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  • #42
BTW, all my rambling about power adapters and batteries in the beginning of this thread was because I didn't understand the Arduino yet. Everything I need is provided by that one board via a USB connection to the computer. Onboard power outlets and whatnot for a multitude of purposes. I'm quite impressed with the thing.

So yes, the Raspberry and the Arduino are two very different "creatures".
 
  • #43
Welp, I had hoped that I could've skimped my way through this and just follow the instructions from some howto - like building a LEGO DUPLO model - but it seems I'm actually going to work for it! This means I'm not getting around profiling my laser beam and actually use some mathematics!

EDIT: Not to mention actually understanding Raman-scattering! I'm completely flabbergasted (and a little outraged)!

Darn!

:woot: