Yes, that's a good suggestion.  Alternately, if you have a lead screw, then the 
slider could activate a set of microswitches, which should give excellent 
longevity, and be quite eay to construct and be eraltively inexpensive.    

David

 with a crankQuoting Bob Ammerman <rammerman@verizon.net>:

> Well if you have a brass crank, why not just a rotary encoder on its shaft 
> and a zero position sensor at one end of the travel of the pointer.
> 
> -- Bob Ammerman
> 
> ----- Original Message ----- 
> From: "ivp" <joecolquitt@clear.net.nz>
> To: "Microcontroller discussion list - Public." <piclist@mit.edu>
> Sent: Friday, February 05, 2010 6:29 PM
> Subject: Re: [EE] Material suggestions for slide switch
> 
> 
> >> 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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