Introduction: Making an EOS 1 Open-source Spectrometer

About: Erie Open Systems is the maker of EOS 1 (Erie Open Spec v1.0), an open-source spectrometer for measuring nutrient concentrations in water

The EOS 1 (Erie Open Spec v1.0) is a simple, open-source, smartphone-based spectrometer designed to be used by any environment-minded person for measuring nutrient concentrations in water.

Please skip to step 5 if you have the official EOS 1 kit.

Design files (STL, DXF) are also published on our Thingiverse page:

Step 1: Laser-cut Acrylic Housing

  • skip if you have the EOS 1 kit (included in the kit)
  • We used a 40W Epilog Laser engraver and it worked fine.
  • DXF file for Laser cutting is also available on our Thingiverse page:
  • use opaque Acrylic sheet 1/8" thick ( for example, the "scratch-resistant Acrylic sheet" is a good choice: )
  • do not use clear Acrylic
  • do not use PVC sheet (toxic fume may be produced when laser-cutting PVC)
  • an EOS 1 can fit in a 12" X 12" sheet
  • Remove cover paper on one side only

Step 2: 3D-print Sample Holder and Slit

Step 3: Clean Out Support Structures on 3D Prints

  • skip if you have the EOS 1 kit (included in the kit)
  • an exacto knife would help
  • don't forget the supports inside the cuvette slots, and try to make the inner surfaces as smooth as possible

Step 4: Install Reflector, LED, and Slit

  1. skip if you have the EOS 1 kit (included in the kit)
  2. cut a piece of Teflon sheet (1/32" - 1/16" thick) which can fit into the reflector gap
  3. wrap a piece of Aluminum foil only on the outside (back side) of the Teflon sheet
  4. insert Teflon+foil sheet into reflector gap
  5. insert a bright white LED into LED hole
  6. align the slit with guide posts on the front surface of sample holder, fix with superglue

Step 5: Assemble

  1. attach mirror (1" square) onto the holding plate with double-sided tape
  2. put things in place as shown in picture
  3. Make sure the side with cover paper faces inward (anti-glaring)
  4. secure the two side plates with screws

Step 6: Install Battery Pack

  • install a current-limiting resistor (10 - 220 Ohm) into one of the slots inside the battery holder, make sure it's spring-loaded
  • use double-sided tape to secure the battery pack onto the bottom plate (again, cover paper faces inside), make sure the switch on the battery pack is accessible from the outside

Step 7: Connect Battery Pack With LED

  1. put two AAA batteries into the battery pack (check and make sure the polarity is correct)
  2. install bottom plate to EOS1
  3. connect wires from battery pack to LED (red wire to long leg on the LED, black wire to short leg)
  4. try switching on and check that the LED lid up

Step 8: Install Diffraction Grating

  1. skip if you have the EOS 1 kit (included in the kit)
  2. cut out a small (approx. 1cm X 2cm) piece of diffraction grating, make sure the long side align with the vertical axis of the cardboard
  3. align the grating with the axis of the top plate (here we've come up with a simple jig with a laser pointer, see picture attached)
  4. secure the grating on the top plate (inside, again, the side with cover paper) with Scotch tape (here we just happened to run out of Scotch tape, so we used Kapton tape)

Step 9: Install Top Plate and Cover Plate

Step 10: Replace Batteries

  • battery pack can be easily accessed by taking the bottom plate off