What I want to do
Make low cost quantitative measurements of the concentration of chemicals in solution. The big problem with using cell phone or webcam based spectrometers is auto-exposure which makes comparing intensities between different spectra basically impossible. Using a LED and battery, a light dependent resistor, multimeter and some laser cut plastic you can measure absorbance quantitatively.
My attempt and results
Check out the blog post I wrote on the experiments http://nznano.blogspot.co.nz/2014/11/low-cost-photon-factory-colorimeter.html I will transfer over some of the notes when I get the design finialised. Basically calibrated the device using nitrate solutions and compared this with a commerical spectrometer.
Questions and next steps
Something I want to explore is how blue LEDs could be used to excite oils fluorescence and green or red LEDs could be used to detect the fluorescence signal. This would allow for the spectrometer to characterise the oil and the colorimeter to determine how much oil is in the sample.