There are two, maybe three LEDs emitting blue light at slightly different wavelengths - It would help if there was a decent spectral response graph available so that "we" could say "to get grade N, you need wavelength Y" for the average VC paper.
Originally Posted by cnmne
But, but... You already have a computer in front of you. A little bit of code, and a few extra minutes with a soldering iron, and you have a high precision timer
Originally Posted by ic-racer