🚀 go-pugleaf

I've been wondering lately about how one might build a very simple and
cheap color sensor.  I have in mind something that would be fairly
reliable in providing 3 or perhaps even 4 bits of discrimination and
which would be fairly reliable given good input, e.g., having a
well-lit piece of colored construction paper put in front.

A photoresistor alone might seem to be enough, given that different
pieces of paper will reflect different amounts of light.  So as a
control, imagine that the sheets have been chosen so that a single
photoresistor gets close to the same reading for each sheet, yet they
are easily distinguished by color.

My first thought was to use three photoresistors with R, G and B
filters (just cellophane, perhaps).  Or perhaps there are tuned
versions that would give the same effect.  Better yet, a single
tunable photoresistor could be used with 3 consecutive readings.  
Are there cheap ways to measure dominant frequency directly?  Etc...

kbasye@black.clarku.edu     
Ken Basye
Dept. of Math and CS
Clark University
950 Main St.
Worcester, MA  01610