This spectrometer is made with cardboard inserts inside an old VHS box, and uses a USB webcam. This allows the user to view the spectrum in real-time, rather than taking a photo and analyzing it later. Please get in touch with jeff@publiclaboratory.org if you'd like to help work on this!

This hardware design will soon be released under the CERN Open Hardware License 1.1. A draft agreement is under development here: http://publiclaboratory.org/wiki/ohl-agreement and should be complete in a few days.

Specs

(these are approximated but we should soon post a page with calibration information)

• around 400-900nm, maybe wider
• 5-10nm spectral resolution
• 20-30 samples per second
• around $30 in materials, drops to around $10 if you use a non-HD webcam
• approx. 1 hour construction time
• Mac and Linux compatible, should work on Windows but untested
• open-source software at: http://github.com/jywarren/spectral-workbench

Goals

Our early goals are to:

• Identify a contaminant in a sample, like Polycyclic Aromatic Hydrocarbons -- like naphthalene, anthracene and tetracene. Tetracene has absorption bands well into the visible range.
• Identify a plant species by its spectrum. (see this helpful paper by Zomer et al) Or perhaps a mineral, using the ASTER spectral library
• Try to identify something in a smokestack plume, like a refinery plume

How to build your own

Software

Download the client software (Linux/Mac, may work in Windows with a little work) here: http://github.com/jywarren/spectral-workbench

Hardware

Instructions on building your spectrometer can be found at:

Video Spectrometer Construction »

Using your spectrometer

You'll need to calibrate it first; the best way is probably to use a known spectrum from a compact fluorescent light bulb, and to compare it to your spectrum like this: http://publiclaboratory.org/notes/warren/7-28-2011/live-spectral-analysis-code-good-resolution

We're starting to compile a listing of spectral databases here: http://publiclaboratory.org/wiki/spectral-libraries

more soon

To do

• find a way to find a spectrum similar to a recorded sample spectrum, from a library of spectra like the ASTER library or the HITRAN library
• create a website to upload spectra to, -- even better, allow them to be sorted into "sets", and allow comments on each spectrum by other users. See the source code for where we've started work
• Investigate the HD camera's spectral response
• Explore how to combine or select the channels for measurements you want to make
  • Implement a technique to do that in the software
• Generalize the methods for others using different cameras (maybe using some kind of calibration parameters that we measure and distribute in the code, or have experimenteers determine the values of the parameters themselves using a sun measurement and some code in the software.

Spectrum gallery

Some spectra captured with one of these devices. If you begin taking spectra, start uploading them to Flickr with the tag #diyspectrometer -- we'll soon have a place to automatically upload them, but this will work for now.

An example spectrum (one of our best yet!):

A Philips "warm" compact fluorescent bulb:

Spectrum of sunlight through water from a puddle at the Gowanus Canal salt lot: