3D-Printed Spectrometer Using a DVD Diffraction Grating for Smartphone

Portable Smartphone Spectrometer

1. 3D-printed spectrometer parts (body, rotary axis, knob);
2. DVD (better resolution compared to CD);
3. Double-sided tape or glue;
4. Ethanol (alcohol) for cleaning;
5. Smartphone with camera.

This DIY project is a portable spectrometer that attaches to your smartphone. It uses a DVD diffraction grating to split light into its respective wavelengths, allowing you to view and analyze visible light spectra using your phone's camera.

Parts to print (STL files attached):

1. Spectrometer body;
2. Rotary axis;
3. Knob.

Printing tips:

1. Use black filament to avoid light reflection inside the chamber;
2. Use 4 perimeter walls for the body to strengthen the arc that secures the spectrometer to the smartphone;
3. No support is needed for the body or knob;
4. Only the rotary axis requires support.

Use a DVD (not a CD), as DVDs have more grooves (lines) per millimeter and provide better spectral

resolution.

Instructions (for DVD+R):

1. Cut the DVD in half with scissors;
2. Gently separate the two layers (transparent and reflective);
3. Clean the reflective layer with ethanol. DO NOT rub it, but let it drain and dry freely. This is needed to remove a dye layer;
4. Cut a rectangular piece for use as the diffraction grating, following the orientation shown in the photos.

Important:

1. Avoid touching the reflective surface to preserve clarity;
2. If you are using a different type of DVD, the method for preparing/cutting the diffraction grating from it can vary;
3. Link to CD/DVD diffraction theory: http://www.ikes.16mb.com/physproj/CD_diffraction2.pdf

1. Attach the DVD piece to the rotary axis, aligning the grooves (the longest side of the rectangle) parallel to the axis. Use double-sided tape or a small amount of glue;
2. Insert the rotary axis into the spectrometer body;
3. Fit the knob on the rotary axis. If printed accurately, no glue should be needed.

1. Before attaching the spectrometer, open your camera app;
2. Focus to the light source and lock the focus;
3. Attach the spectrometer in the phone;
4. Adjust the rotation angle in the knob (around 14 degrees) for the best spectral view;
5. Adjust screen brightness for better clarity.

Analyzing various light sources:

1. RGB LEDs: separated red, green and blue colors;
2. Incandescent or halogen lamp: continuous spectrum;
3. Fluorescent lamp: lines;
4. UV lamp: lines; ATTENTION: Protect your eyes with proper goggles;
5. High-pressure sodium lamp (street illumination): lines and broad spectrum.

Curiosity: The yellow street lamps commonly use high-pressure sodium vapor, and their spectra are dominated by strong emission around 589 nm. However, at high operating temperatures, a self-absorption line can appear near 589 nm, caused by absorption of emitted light by the cooler outer layers of sodium vapor in the discharge.