> Is there a simple or at least an inexpensive way to measure the spectrum
> of a light source?

Yes - and it's the same method used in some real and often expensive
instruments/
Use a diffraction grating to split the light into a spectrum and move
a photo detector across the output (or use a moving mirror) or use a
linear multi element detector.

Diffraction gratings of acceptable performance for playing may be
produced by using part of an unrecorded recordable CD.
"Real" gratings can be had for prices from about nothing through forget-it.

Much on web under spectrometer and diffraction grating.
Various DIY designs.

_____________

Yee Ha / Wow

https://www.google.co.nz/search?q=3Dspectrometer+diy&hl=3Den&tbo=3Du&tbm=3D=
isch&source=3Duniv&sa=3DX&ei=3DDOn1UNWXKvCwiQeV7YGoDA&ved=3D0CFgQsAQ&biw=3D=
1536&bih=3D840

______________

Digital camera, piece of CD, cardboard and tape.
Impressive results considering.
http://blizzard.rwic.und.edu/~nordlie/spec/

___________

Kickstarter
$35 kit
That tells you how hard it isn't
This analyses a sample that is filtering a light source BUT the
extension (or subset) related to LEDs is obvious

http://www.kickstarter.com/projects/jywarren/public-lab-diy-spectrometry-ki=
t

http://publiclaboratory.org/tool/spectrometer

http://www.engadget.com/2012/08/28/insert-coin-public-lab-diy-spectrometer-=
wants-to-be-the-shazam/

__________

Open hardware
Free software
And/or buy now
http://myspectral.com/

______

Spectra glasses + webcam / cellphone cam
http://www.wired.com/wiredscience/2012/07/diy-spectrometer/



          Russell McMahon
--=20
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