r/engineering • u/International-Net896 • 6d ago

Home-made spectrometer (beta) [PROJECT]

https://www.youtube.com/watch?v=e9Ja7LYqQIM
45 Upvotes

95% Upvoted

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u/avrguy004 5d ago

op, if you added a relatively white light source and then focused the light into a tiny beam, a prism/diffraction grating with a way to move the split beam into its relative colors and a ldr or a linnear ccd array to measure its value it could offer better precision, lastly to be more accurate you could instead of a tube use a cell that has 1cm from wall to wall, because of a math formula to calculate the absorbance of the material you test * (something like spectrophotometer cell or similar to its dimensions that will allow the flow of the liquid too)

edit: *Beer-Lambert law

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u/codiciltrench 5d ago

I love this sub, I’m not an engineer, I have no idea what a single sentence meant.

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u/avrguy004 5d ago

Its how to make a basic spectrophotometer (knowledge from various yt vids and actual reshearch) 

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u/International-Net896 5d ago

Yes, I know. But I wanted to try a new approach with no optics like a prism, diffraction grating, slits, lenses, and mirrors and compensate for the low resolution with different interpolation methods like Lagrange or cubic spline interpolation. Furthermore, to get the full UV/VS spectra you need a deuterium lamp and a tungsten/halogen lamp when using a prism or grating. Btw., with 6 LEDs and 9 photodiodes in the AS7341 sensor, which are individually addressable, you could reconstruct a possible shape of the actual spectrum with up to 54 degrees of freedom.

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u/avrguy004 5d ago

With a set of rgb leds you can play also with pwm to make various color combinations, forthe previous i just suggested all these for accuracy and as light source i meant simply a white led lamp nothing expensive, also i saw you tried to measure chlorophyll for that you could used a 400-430nm, a 600nm and a 650-680nm peak led for a approximate chlorophyll consentration

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u/International-Net896 5d ago

The colors produced by pwm and RGB Leds wouldn't be monochrome:) For the next iteration, I want to make the LED ring easily replaceable and add many more LEDs.

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u/FrontStriking3042 4d ago

I love DIY scientific equipment projects like this! Will you be posting schematics/documentation?

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u/International-Net896 3d ago

I will publish all files on github but it can take a while.

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u/FrontStriking3042 2d ago

Much appreciated, and certainly understood. People willing to share these sorts of things are heroes for everyone.

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u/nebulous_eye 3d ago

May you please share the CAD files for the parts you printed?

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u/International-Net896 3d ago

I will share all files, STL, gerbers, source code, etc. But it can take a while.

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u/[deleted] 2d ago

[removed] — view removed comment

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u/aprilla2crash 2d ago

Please you forgot the word please. This person put probably weeks/months of work into this

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u/WebAffectionate9131 2d ago

looks good!!

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u/antiduh Software Engineer 5d ago

I can't watch videos at the moment, can you summarize your work? I'm very interested.

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u/International-Net896 5d ago

I just copy-paste the video description if that is ok for you:

In this video, I show the building and operation of an experimental 3-D-printed spectrometer. It is based on discrete LEDs with specific wavelengths placed on a ring rotated by a stepper motor. The measured values are then used as supporting points for three interpolations (Lagrange, linear, and cubic spline). Another possibility of the spectrometer is to combine the spectral emission of the LEDs with the spectral sensitivity of the sensor's photodiodes (the AS7341 has 9 photodiodes that can be addressed individually). I also use a flow-through cell for continuous measurements, which are used, for example, in a flow injection analysis device.

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u/Medical-Bake-9777 20h ago

Damn that’s cool