With a little help from the junkbox and a couple of minutes time, you can fabricate a very usable optical quadrature shaft encoder that has 256 counts/revolution (64 windows on the encoder wheel).
http://members.shaw.ca/swstuff/mouse.html I used the above encoder on a vector network analyzer project detailed at http://members.shaw.ca/swstuff/vna.html The local thrift store sells PC mice for $0.49. This will yield 2 or 3 encoder channels worth of parts. Have fun. -- ===================================================================== Lawrence Glaister VE7IT
