OK...back to playing with my QRD1114 circuit!!!

  I'm a little bit confused. No issus on turning it on, its just a LED so
  3.3V, using a 120ohm resistor, gives me a lil over 21mA drive, within
  spec.

  Now, on the output side ive seen several different applications, some 
  make sense, others don't. I had just simply tied the emitter to ground
  and used a pup on the collector so the harder the transistor turned on, 
  the more current flow and the higher the voltage across the resistor
  (feeding to the A/D of the PIC).

  But, this application.... http://roborific.com/node/73 has the collector
  tied to ground, and the emmiter to the "detector" circuit. I can't see 
  how that works ? I suppose its all to do with the current into the detector
  if its a positive flow?

  And then on http://www.parallax.com/dl/docs/prod/compshop/qtilinesensorrev1.pdf
  it has a cap tied from the Vcc rail to the collector, to give a positive reference (?)
  and then a series resistor to the PIC input. Again, this is a current limit for how 
  hard the transistor is turned on?


  So whats the best method to give the best response?  I'm going to experiment some
  just want some opinions


  JJ 


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