[sdiy] DIY slide-bars

[Rainer Buchty]

>1) How did these classic slide bars work? What materials etc. was there?

In the Elektor magazine they just used graphite, i.e. you literally drew
the slide bar, but then had a metal probe for sliding so your finger
stayed clean :)

>2) How could one make one today? I am looking for a fairly stable design, so
>   antistatic foam is out, OK?

I wonder if recording tape could be used in a setup like this:

	========	cover foil
        --------	recording tape
	________	copper or some other conductor

The copper is attached to some sensible voltage. The recording tape
basically acts as a trimmer, so that touching -- thus closing the
contact -- is equivalent to the wiper. Now you take the difference (or
better: the ratio) between the voltages measured at the ends of the tape
and get the tap position. Could probably be further refined if the tape
is crescendo-shaped.

(I'm quite sure people on this list have done something like this before 
and can tell me why that's a bad idea.)

Rainer