Re: Apple II's paddle 3 button

[mjmahon@aol.com (Michael J. Mahon)]

Dave Althoff Jr replied:

<snip>

>It is most certainly not a mechanical bounce, as you suggest.  I suspect
>the problem is with the edge of the target, complicated further by the
>fact that I am shooting through a Ferris wheel structure with *two* spokes
>between the emitter and detector.  I'm getting multiple state changes
>every time a spoke goes by.  I'm wondering if I should add a cap to the
>circuit to slow the hardware response time just a little.
>
>It has been a while since I looked at the program, too.  Conveniently, the
>Wheel has 16 seats (identified, of course, as 0-F).  Using the single
>detector, I should be able to calculate which seat is approaching the
>boarding platform, and even come up with motor control to bring the system
>to a smooth stop at each seat.  (I already have a PWM motor control
>program...one of the annunciators controls the DC motor switch.  Works
>kinda neat!)

I think I understand--there is a spoke on each side of the wheel, and
you are sensing by shooting a beam of light from one side of the wheel
to a phototransistor on the other side.

You should be able to fix this easily by offsetting the light source
and the photodetector so that the beam passes through the wheel
at an angle, and each spoke produces a distinct pulse.

This will give you 32 pulses per rotation, for twice the angular
resolution.  ;-)

It will be very difficult to use a timing-related method to fix the
double-pulse problem you have now, since what works at one
speed of the wheel will not work at another.  This is why it is
best to simply sense _both_ spokes distinctly.

-michael

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