Public Lab Research note

a paper spectrometer design, pt 2

by mathew | December 06, 2014 02:34 06 Dec 02:34 | #11440 | #11440

mathew was awarded the Basic Barnstar by Francis for their work in this research note.

What I want to do

This is a substantial revision to an earlier design, which integrated a bunch of other earlier design concepts.

The earlier version came back from the Barnraising a little crunched. While the idea of being able to print the whole thing out on 8.5"x11" pieces of paper is something I really like, the three-piece design was a little fragile.


I figured that a stiffer material was needed, with fewer exposed tabs. I also wanted to introduce more flexibility and modularity into the design.

My attempt and results

Finishing what I started

I started out by finishing up and revising the files for the printable version and integrating everyone's comments. Now the fold lines are dashed, the tabs are more protected, and the grating is at a 65 degree angle. @fastie was right that the 65 degree angle gets a slightly clearer spectra. See my earlier note for assembly instructions.






A New Case

Then I designed a new box, with a little trial and error and a a good bit of patience. I started with cardboard, but that was too thick.


So I went to paperboard, essentially a black card stock about the thickness of a cereal box, and reworked the cardboard into to this pattern:



you will also need a board 5mm x 40mm x 235mm, some velcro, and this mounting angle for the grating:


I couldn't fit the box design all on one sheet all at once, and had to cut it up a bit.


I crimped the folds into the material by running over the fold lines with a ball point pen really firmly. This makes great creases and destroys ball points.

IMG_20141204_173356.jpg IMG_20141204_174649.jpg


Then I started putting the parts together. The mounting board is masonite, 5mm x 40mm x 235mm, and covered in velcro. The block is a 45 degree angle block that ships with the existing desktop spectrometer. It is attached with velcro, as is the angle for the diffraction grating.


The collimation slit mounts on a 4cm x 6cm card and slides into a pocket in the front, locked into place by the top of the boxes' tabs. The idea of a little pocket for collimation slit cards was @amysoyka's.




The double-folded walls of the spectrometer make it really stiff and durable, and quite crunch-resistant, the velcro means that the distances can be changed, and the grating can be changed or re-mounted on a new angle, and the slit can be easily interchanged. The front tabs will also allow it to click into an oil testing kit sample station (more to come).

I haven't had a chance to really play around with this one as a spectrometer, but the initial spectra I captured (there was some weirdness on spectralworkbench today owing to a server switch) looked very clear.

Questions and next steps

Tell me what you think!

The mount for the grating needs to be a little narrower, as opening and closing the lid can sometimes tork it a bit.

also: Me and @warren brainstormed some ideas as to how to give credit to all the contributors to the oil testing kit in the design, and I asked if we could print the names of people's notes directly on the kit. Jeff said that there are shortened URLs that are just numbers for research notes. I'm going to put some printing on the outside of the different parts.



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Also, i made the shortlink feature -- see in the subheader "shortlink" -- for example this page's is:

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Great job Mathew!

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This is SUPER, can't wait to fold one myself

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new top and bottom: I split this into two pieces for printing reasons. specbox-top.pdf spec-box-bottom.pdf



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<3 This is awesome. Thanks for the tag.

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refined the tabs so they are die-cuttable, more refinements after a first round of laser cut versions. I switched to blue fold lines for the laser cutter.





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a lot of small revisions based on the die-cuttable tabs.



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PDFs for images in previous comment.



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Looks amazing. I recently saw some neat ideas for cardboard construction from Nadya Peek and James Coleman, and also was just impressed at their documentation:

They also had some ideas for connective technologies:

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I love their HTML 5 video stuff in there. really nice. The fold-up GIF is also stellar.

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