> You may have already thought of using a rotary potentiometer with
> a ~100mm diameter pulley on it, and use a string attached to the slide,
> in the style of a dial cord in old radios.

If it's robust enough in the long term (got a bit of a downer on carbon pot
tracks but you can get conductive plastic, at a price) that might be a goer

The client has indicated he'd like the slider moved by a brass crank. !!!!
This probably means that the slider will be on a lead screw and several
turns of the crank will move the pointer from one item to the next

The reason being that this is a museum exhibit of a 1906 Edison cylinder
player, which has been motorised but originally was wound up with a
crank, so he wants to keep some of that feel to it. The selector is to pick
a song to play from a bank of WAV files

If the resolution proves too fine for the ADC to differentiate 20 positions
reliably I should be able to come up with a scheme to divide the pot travel
across more than 1 ADC

As the slider has to move a great deal further than the pot shaft some
step-down gearing would be needed to convert 200mm linear movement
via a lead screw to 270 degrees of pot rotation

I even thought of a stepper motor as a pulse-emiting encoder but can't
guarantee that it will keep track or be returned to an end stop to reset the
pulse count

My idea with a long PCB is that it would have fixed resistors and solid
detentes, thus turning the crank is a WYSIWYG. It's for public use and
something I'd rather not have to service or field complaints about

wbr 

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