[sdiy] DIY slide-bars

[The Peasant]

I would expect that the low resistance of Nichrome would be problematic. The 
best idea that I have heard of for a ribbon is to unroll the internal element 
from a wirewound multi-turn potentiomenter and use that. I certainly would not 
expect to have any drift with this type, although I have not actually tried it 
myself.

Take care,
Doug
______________________
The Electronic Peasant

www.electronicpeasant.com


Quoting "Brett, Bill" <BJB at dolby.com>:

> Nichrome wire seems to be readily available over the web. Has anyone
> tried this stuff?
> 
> -Bill
> -----Original Message-----
> From: owner-synth-diy at dropmix.xs4all.nl
> [mailto:owner-synth-diy at dropmix.xs4all.nl] On Behalf Of Gene Stopp
> Sent: Tuesday, July 27, 2004 5:24 PM
> To: synth-diy at dropmix.xs4all.nl
> Subject: RE: [sdiy] DIY slide-bars
> 
> 
> I've done two experiments with two different types of material.
> 
> First experiment: black antistatic bag material (opaque and rubbery),
> cut into a strip. Second experiment: conductive rubber cord (maybe 1/8"
> dia.) used for EMI gaskets. Both of these materials had a fairly high
> resistance per distance (several K per inch). What this caused is
> non-linear behavior and moving voltage points (i.e. yesterday 2 volts
> may be right *here*, and today it's over *here*, a couple inches away).
> Something like the Moog controller is more stable and repeatable,
> meaning you could mark the fingerboard with the voltages and they'll
> always be at the same places. I think it's because the resistive element
> was a pretty low resistance, driven by higher current. This would imply
> some kind of heating element wire, like in an electric heater. It may be
> only a couple of ohms so something like a power regulator might be
> needed, perhaps configured in constant current mode.
> 
> I've not run across such an element yet but I do have a note to self to
> be on the lookout for the next trashed bathroom heater or hairdryer.
> 
> - Gene
> 
> 
> -----Original Message-----
> From: owner-synth-diy at dropmix.xs4all.nl
> [mailto:owner-synth-diy at dropmix.xs4all.nl]On Behalf Of Rainer Buchty
> Sent: Tuesday, July 27, 2004 6:57 AM
> To: Magnus Danielson
> Cc: synth-diy at dropmix.xs4all.nl
> Subject: Re: [sdiy] DIY slide-bars
> 
> 
> >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
> 
> 
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