[sdiy] DIY slide-bars

[harrybissell]

I expect that drift would not be much of a problem either way. Rather that contact

resistance vs the element resistance would be an issue.  The voltage drop in solid

nichrome wire must be small, therefore very high impedance pickup and lots of
gain so contact resistance is a small error...

higher currents ??? can you say "toaster element" ???

H^) harry

The Peasant wrote:

> 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
> >
> >
> > -----------------------------------------
> > This message (including any attachments) may contain confidential
> > information intended for a specific individual and purpose. If you are not
> > the intended recipient, delete this message. If you are not the intended
> > recipient, disclosing, copying, distributing, or taking any action based on
> > this message is strictly prohibited.
> >
> >
> >