Detect green (but not red) LED lighting up?

My Motorola Triumph phone (in fact lots of people’s Triumph phones) has this mysterious behavior where the green notification LED will sometimes flash (there are never any actual notices to be found when this happens). I’m wondering what the simplest way might be to detect it (and distinguish it from the red LED which does all sorts of legitimate flashing I’d want to ignore).

I’m thinking if I get curious enough someday, I might want to have an arduino watch for the green LED then tell my computer to capture the log from the phone as soon as it lights up :-). Maybe I’d be able to find a pattern and discover what is behind these mysterious green flashes…

For some indubitably strange reason Green LED's will have a much higher output voltage when exposed to green light BUT it takes an Op-Amp and some minor experience to use them for that purpose as the output is a current rather than a voltage and needs a lot of gain to turn it into a real signal for an Arduino.


Take a look at Arduino Playground - HomePage

Similar to what Doc said above a green LED should respond differently than a red.

Put a filter over a photocell (green) then only the green light will excite the photocell which you use to trigger a transistor which, in turn, triggers the arduino input