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! ##Specs## (these are approximated but we should soon post a page with calibration information) * ~400-900nm, maybe wider * 5-10nm spectral resolution * ~20-30 samples per second * ~$30 in materials, drops to ~$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](http://publiclaboratory.org/notes/warren/8-5-2011/uv-visible-spectral-features-benzine-and-some-pahs). Tetracene has absorption bands well into the visible range. * Identify a plant species by its spectrum. (see [this helpful paper by Zomer et al](https://publiclab.org/sites/default/files/Zomer_2009.PDF)) Or perhaps a mineral, using the [ASTER spectral library](http://archive.publiclaboratory.org/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, may work in Mac or Windows with a little work) here: http://github.com/jywarren/spectral-workbench ###Build instructions### You'll need: * a black VHS box, like from Blockbuster * a letter or A4-sized sheet of stiff black card paper * a USB webcam, preferably over 640x480/VGA resolution, 780 HD is best. * an old but relatively unscratched DVD-RW (a CD can work too) * white glue and scissors/X-acto knife, some tape _more plans coming soon, but see this image for starters:_ ##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 ##To do## * find a way to find a spectrum similar to a recorded sample spectrum, from a library of spectra like the [ASTER library](http://archive.publiclaboratory.org/aster-spectral-library/) or the [HITRAN library](http://archive.publiclaboratory.org/hitran-spectral-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](http://github.com/jywarren/spectral-workbench) for where we've started work ##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: