Hi All,  I find myself becoming distracted by the people discussing
reading music rolls.  I am in the middle of building a roller organ
when I see some neater ideas come floating by.

To Craig Brougher:  Lets say we buy a three foot piece of hard plastic
tubing the diameter of a fuse.  This stock can be found in tropical
fish stores.  We allow a metal ball to float in the tube.  We melt two
pins in the tube so the ball can only move up and down one inch or
less.  We can send light via a photo sensor through the sides of the
tube (file the sides flat and polish them).  We could set it up so the
signal goes on or off when the ball is pulled up.  A small spring could
also be used to dampen the movement of the ball (a variation of your
bubble idea).

To Horst Mohr: Your fiber optics is a great idea.  The only change I
would make is to add op-amps [operational amplifiers] to the output of
each fiber.  The op-amps can be setup to read a wider range of light
intensity and turn it into a cleaner on and off signal.  This would
eliminate the need to make adjustments due to the different in trans-
lucent properties of paper.  If you could see how the infrared is
lighting up the paper you would quickly switch to incandescent bulbs.
I made a spinning drum scanner years ago and the infrared diode was
reading the drum under the picture.

Okay,  now I can go back to my project! <Grin> Keep those ideas
coming.

John Conrad Kleinbauer
Kleinbauer@juno.com

 [ Good ideas, John.  My biggest headache with the infra-red emitters
 [ and detectors was the stability.  Both the gain and the bias drift
 [ slowly.  I guess that the IR emitting diodes are better nowadays,
 [ but I've learned that photo-transistors are no better than twenty
 [ years ago.  A better device is a photodiode with a separate ampli-
 [ fier, as you suggest, but that adds even more parts. -- Robbie