Hi all,

I got a few replies about just using resistors to scale the voltage with
a 3 X 4 keypad. The reason for the 317 is that I can get a reasonably
linear relationship between resistance and voltage. If you use resistors
the change becomes logarithmic and the voltage difference becomes tight
at one end of the scale. It's quite a tall order selecting appropriate
resistors.

I tried to implement the idea with a single digital IO pin, but I'm not
sure it can be accomplished. The pin would need to monitor for a
keypress to start a conversion (capacitor charge) and then detect the
switching threshold.

It could probably be done with 2 pins, but it may be a waste of time
considering there can be 100's of ohms variation in the keypad due to
manufacture and finger pressure on the keys.

Interesting problem though.

--
Best regards

Tony

Multimedia 16F84 Beginners PIC Tools.
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