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DIY Raspberry Pi Spectrometer Guide

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Re: DIY Raspberry Pi Spectrometer Guide

#21
post #3

Unfortunately, light spectrometer, not mass spectrometer. I'd love a DIY mass spectrometer or liquid chromatograph for biohacking!

https://www.open-raman.org/ You can try building that one. It's a DIY raman spectrometer.

Also a neat write up of a DIY near-IR spec here: https://caoyuan.scripts.mit.edu/ir_spec.html

I'm still holding out hope someone will make an open source FT-IR design. I actually need one for a project I'm working on, and I'd prefer not to shell out thousands of dollars for a used machine.

Re: DIY Raspberry Pi Spectrometer Guide

#22

$70 seems expensive for a diffraction grating, what am I missing?

There's very little use for a general purpose grating, since all commercial uses end up with custom gratings directly from manufacturers. So the ones that are sold in catalogs tend to be more expensive owing due to economies of scale, maintaining an inventory, and probably passing through one or more middlemen. And people willing to pay R&D prices to have something quickly drive up the price as well.

How does it compare to a diffraction grating that costs $2? Quickly Googling this I found: https://www.homesciencetools.com/product/diffraction-grating...

One of the reviews on that page mention implementing a spectrometer:

> The 1,000 lines/mm Diffraction Grating Plastic Film was used to make a high resolution optical spectrometer. First, the film was removed from its paper 2" x 2" card stock. The crystal clear film was next glued to an optical ring that was mounted in front of a very inexpensive 1,920 x 1,080 pixel webcam. The modified webcam was placed in the back oRead more about review stating Using the 1,000 line/mm Diffraction Grating in a Spectrometerf a pinhole camera-box and mounted at an incident-angle to the incoming light beam. In this configuration different light sources could be introduced to the new spectrometer and their light spectrum captured using a USB-computer input. Thus, a wide variety of light sources could be fully analyzed at a resolution of about +/- 2nm. Using this very inexpensive (1,000 lines/mm) grating, coupled with an equally inexpensive webcam, a high resolution optical spectrometer could be built for under $25.00

Re: DIY Raspberry Pi Spectrometer Guide

#24
post #21

Earlier quoted context omitted.

https://www.open-raman.org/ You can try building that one. It's a DIY raman spectrometer.

Also a neat write up of a DIY near-IR spec here: https://caoyuan.scripts.mit.edu/ir_spec.html I'm still holding out hope someone will make an open source FT-IR design. I actually need one for a project I'm working on, and I'd prefer not to shell out thousands of dollars for a used machine.

What are the key hardware differences between near IR and FT-IR? Could they be overcome with some software assisted analysis?

Re: DIY Raspberry Pi Spectrometer Guide

#25

Earlier quoted context omitted.

There's very little use for a general purpose grating, since all commercial uses end up with custom gratings directly from manufacturers. So the ones that are sold in catalogs tend to be more expensive owing due to economies of scale, maintaining an inventory, and probably passing through one or more middlemen. And people willing to pay R&D prices to have something quickly drive up the price as well.

How does it compare to a diffraction grating that costs $2? Quickly Googling this I found: https://www.homesciencetools.com/product/diffraction-grating... One of the reviews on that page mention implementing a spectrometer: > The 1,000 lines/mm Diffraction Grating Plastic Film was used to make a high resolution optical spectrometer. First, the film was removed from its paper 2" x 2" card stock. The crystal clear film…

I'm no optical engineer, but I suspect one issue with those types of plastic gratings is ensuring the flatness of the surface; its just a thin sheet of plastic so I'd expect it to buckle/wave around quite significantly. More serious gratings are solid chunks of glass instead.

Re: DIY Raspberry Pi Spectrometer Guide

#26

OT question: Is it possible to use a wedge-shaped slit (uneven width) to increase the dynamic range of a slit-grating-camera phone spectrograph? Backstory: I've repeatedly encountered deep confusion about color, even among first-tier physical-sciences graduate students. Yet color is widely taught K-2. Apparently without great success. So what might a rewrite, a modern learning progression for color, look like? Perhap…

Why. All models are flawed, some are useful. Kids learn mixing paints, that's useful for arts and crafts. Students learn more advanced models depending on their needs.

Re: DIY Raspberry Pi Spectrometer Guide

#27

Earlier quoted context omitted.

There's very little use for a general purpose grating, since all commercial uses end up with custom gratings directly from manufacturers. So the ones that are sold in catalogs tend to be more expensive owing due to economies of scale, maintaining an inventory, and probably passing through one or more middlemen. And people willing to pay R&D prices to have something quickly drive up the price as well.

How does it compare to a diffraction grating that costs $2? Quickly Googling this I found: https://www.homesciencetools.com/product/diffraction-grating... One of the reviews on that page mention implementing a spectrometer: > The 1,000 lines/mm Diffraction Grating Plastic Film was used to make a high resolution optical spectrometer. First, the film was removed from its paper 2" x 2" card stock. The crystal clear film…

Most spectrometers use either reflection gratings, or holographic transmission gratings that are tailored for optimal efficiency to the wavelength range of interest, and also have exceptional flatness, surface quality, and so forth. "High resolution" is relative, and there are a lot of other figures of merit for spectrometers.

This is a prominent US supplier, and they offer a lot of useful info at their site:

https://www.gratinglab.com/Home.aspx

With all that said, the plastic grating is a very cool thing, and with it you can demonstrate pretty much all the basics of gratings and spectrometers.

Re: DIY Raspberry Pi Spectrometer Guide

#28

OT question: Is it possible to use a wedge-shaped slit (uneven width) to increase the dynamic range of a slit-grating-camera phone spectrograph? Backstory: I've repeatedly encountered deep confusion about color, even among first-tier physical-sciences graduate students. Yet color is widely taught K-2. Apparently without great success. So what might a rewrite, a modern learning progression for color, look like? Perhap…

Why. All models are flawed, some are useful. Kids learn mixing paints, that's useful for arts and crafts. Students learn more advanced models depending on their needs.

> Why. All models are flawed, some are useful. Kids learn mixing paints, that's useful for arts and crafts. Students learn more advanced models depending on their needs.

:) Partly-in-jest paraphrase: Most all models used in science education are needlessly ghastly flawed, leaving students and their teachers steeped in misconceptions. Some are useful - for important exams, or for collaborating with teachers in pretending topics are understood, though vanishingly few provide transferable or operational understanding, let alone integrated or interdisciplinary or rough-quantitative understanding. Students develop less dysfunctional understanding depending on their needs, which can be surprisingly limited. For examples, students empirically don't need to know the color of the Sun to be first-tier astronomy graduate students, nor the order-of-magnitude size of cells to be first-tier medical graduate students, so teaching the wrong color for the Sun, starting in K and continuing into undergrad intro astronomy, and teaching size/scale unsuccessfully from middle-school through undergrad, are in some sense not failing to meet student needs.

Shrug, ok. Also, it's unclear society needs, wants, or would appreciate, or even tolerate, students making sense of the physical world.

But... it can be fun, to at least discuss and explore, how we might go about it, were that an objective to be intensively pursued. No?

Re: DIY Raspberry Pi Spectrometer Guide

#29
post #7
post #2

What would happen to the quality if the diffraction grating spectroscope were replaced with a prism?

That can work too. You have to work out the range of angles that a given prism produces, not an unsolvable math problem.

Adding one more thought, an efficient prism can be more efficient than an inefficient grating. Gratings tend to be preferred in commercial spectrometers because the grating equation has fewer parameters that can fluctuate, and reflection gratings can cover wavelength ranges where there are no convenient optical materials with sufficient dispersion to be practical.

Re: DIY Raspberry Pi Spectrometer Guide

#30

Earlier quoted context omitted.

Why. All models are flawed, some are useful. Kids learn mixing paints, that's useful for arts and crafts. Students learn more advanced models depending on their needs.

> Why. All models are flawed, some are useful. Kids learn mixing paints, that's useful for arts and crafts. Students learn more advanced models depending on their needs. :) Partly-in-jest paraphrase: Most all models used in science education are needlessly ghastly flawed , leaving students and their teachers steeped in misconceptions. Some are useful - for important exams, or for collaborating with teachers in preten…

There are many intentional omissions because people can't afford to study too many years on a curriculum. If you're interested in exploring this issue, perhaps consider what priorities an education ministry would have. For most, knowledge is a means to an end, not an end unto itself.
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