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Public Lab Research note


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Build a papercraft spectrometer for your phone -- version 2.0

by warren |

After a few years, we're returning to one of our oldest kits to update and improve it, building on lots of community-contributed ideas, improvements, and refinements. This page guides you through assembling this new design; also check out this page for related resources and activities.

Our goals were:

  • more rigid/robust
  • printable on non-black paper
  • easier to cut out with just scissors
  • put more of the instructions on the object itself, like on the Antikythera Mechanism

Keep in mind -- this is the "introductory" design intended to onboard newcomers to the project, so we're trying to make it as easy as possible to build. Once you've made this, you're ready to move on to more complex projects, like scanning, sample preparation, and more robust designs.

We haven't gotten all the way there on every goal -- we'd hoped to make a version that required no glue -- just locking tabs -- but we just couldn't keep it small enough to be printed on a folded-in-half letter sheet. See this note, this, and some of these photos for my process of integrating all these changes, and see this page for some of the many many people who've contributed.

What you'll need

Printing and paper

We're going to carry kits in the Public Lab Store soon, but if you're printing this out yourself on a laser printer, keep a few things in mind:

  • print it on some thick paper, like 80 lb cover or cardstock
  • don't jam up your printer!
  • some printers work better than others - our desktop Brother printer's ink rubbed off, but the office's big Xerox printer worked great
  • black and white is fine
  • print it at 100% scale

Note that if you print or paint black ink over the reverse side, the interior of the spectrometer will be darker; you can also color the back side with a black marker or ink.

You can also print it onto thin white paper and glue it onto a sheet of thicker black paper.

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1. Cut out the outline along the red lines

(these may be grey if printed black & white)image description

2. Use a butter knife or ball-point pen to score the dotted lines

This will make it easier to fold evenly. A dull knife or the back side of a butter knife works well - just don't actually cut the lines! It's more like slightly crushing the paper, ideally.
image description

3. Fold over and cut out the "windows" at A1, A2, & A3

This was our attempt to make it easier to cut out the holes in the center of the page without using an Exacto or box knife or a nail; it's not perfect so if you have a paper knife and mat, go for that. image description

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4. "Mountain" fold along the dotted lines, and "Valley" fold along dashed lines

Mountain folds place the creased edge towards you, while valley folds face away from you. Like mountains and valleys, when you lay the paper on the table:image description

5. Cut, peel, and attach DVD fragment

Now, take a DVD-R and (really!) cut into it as you would cut a wide pizza slice.

Once you have your slice, carefully peel the opaque layer away from the purplish transparent layer; keep the transparent one. Try to get a piece with no foil on it, especially near the outer edge.

Firmly tape the slice onto the reverse (blank) side of the large hole you cut earlier.image description

6. Tape the slit over window A2

The kit we sell comes with a slit printed on photographic negative, but there's nothing special about it; it's just a narrow slit for light to pass through.

(You can make your own with two pieces of black paper); trim as needed. See web link for more.image description

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7. Align tabs B, C, D & E and tape them down

Here we've used some adhesive dots; just be sure there's no open seams where light can leak in.

Fold the smaller side over the larger side and tape or glue the side shut.

Now fold over and tape down the two overlapping front flaps -- first the one where you put the slit, then the other to cover and secure it.

image description

Finally, you can tape down the large diagonal flap on the back. This is the surface you'll attach (tape, glue, whatever) to your smartphone or webcam.

In this picture, I've taped the DVD on the outside instead because it kept getting pushed down when it was on the inside; I'm not sure which is better -- what do you think?

image description

Now you're ready to attach it to your phone, webcam, or Raspberry Pi camera, and calibrate it using Spectral Workbench.image description

You're done!

Go to this page to find activities like calibration, different tests you can do, and see the latest design challenges to solve:

PublicLab.org/wiki/paper-spec

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Older versions

As we update the design, we'll try to keep older versions here for the record: https://github.com/publiclab/papercraft-spectrometer


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