Lab-on-an-Arduino Spectral Absorbance Shield aka Optical Density Meter

This Arduino Shield allows to measure the optical density (OD) aka turbidity through a standardized cuvette. 3-Channels for different wavelengths, using 5mm LEDs. The design fits nicely a TIL-99 phototransistor.

see details on: http://hackteria.org/?p=2194