[sdiy] Making a log pot into a linear with precision

[David G. Dixon]

Karl,

According to my calculations, a 100k log-taper pot wired as a variable
resistor (one end tied to the wiper), in parallel with a 47k resistor, would
make a pretty decent 32k linear variable resistor.  Values scale with the
total pot resistance.

Any other opinions?

David G. Dixon
Professor
Department of Materials Engineering
University of British Columbia
309-6350 Stores Road
Vancouver, B.C. V6T 1Z4
Canada
 
Tel 1-604-822-3679
Fax 1-604-822-3619
 
"PERFECTA FINGAMUS SERVIAT NATURA"
 
The information in this email and in any attachments is confidential and
intended solely for the attention and use of the named addressee(s).  It
must not be disclosed to any person without the writer's authority.  If you
are not the intended recipient, or a person responsible for delivering it to
the intended recipient, you are not authorized to and must not disclose,
copy, distribute, or retain this message or any part of it.
> -----Original Message-----
> From: synth-diy-bounces at dropmix.xs4all.nl [mailto:synth-diy-
> bounces at dropmix.xs4all.nl] On Behalf Of Karl Ekdahl
> Sent: Friday, February 13, 2009 8:41 AM
> To: synth-diy at dropmix.xs4all.nl; Matthias.Herrmann at jeppesen.com
> Subject: [sdiy] Making a log pot into a linear with precision
> 
> 
> Hi list
> 
> I'm currently modifying a Digitech Whammy to accept control voltage over
> it's pitch shifting and i need the pitch amount to be controlled with a
> slider and be precise. Turns out tho that all nice slide-pots are
> logarithmic and the Whammy is inherently linear in its response so i'm
> wondering if there's a precise way of linearizing the output of the slider
> without going digital? I'm unsure whether the trick of putting resistors
> around it would cut it since these sliders never have a true log-curve,
> but perhaps it'll be precise enough?  Any input highly appreciated, i'm
> going to publicize all my mods once their finished.
> 
> Karl
> 
> 
>       __________________________________________________________
> Ta semester! - sök efter resor hos Kelkoo.
> Jämför pris på flygbiljetter och hotellrum här:
> http://www.kelkoo.se/c-169901-resor-biljetter.html?partnerId=96914052
> 
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at dropmix.xs4all.nl
> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy