[sdiy] Endless pots?

[karl dalen]

Sorry, it should be 90 and 180deg.

Reg
KD

--- Den tis 2010-12-07 skrev karl dalen <dalenkarl at yahoo.se>:

> Från: karl dalen <dalenkarl at yahoo.se>
> Ämne: Re: [sdiy] Endless pots?
> Till: synth-diy at dropmix.xs4all.nl, "Mike Pepper" <profpep at hotmail.com>
> Datum: tisdag 7 december 2010 02:27
> 
> 
> --- Den sön 2010-12-05 skrev Mike Pepper <profpep at hotmail.com>:
> 
> > Från: Mike Pepper <profpep at hotmail.com>
> > Ämne: Re: [sdiy] Endless pots?
> > Till: synth-diy at dropmix.xs4all.nl
> > Datum: söndag 5 december 2010 18:39
> > I can see a couple of snags in the
> > endless pot idea; when the slider hits
> > the deadband the output voltage is indeterminate, and
> as
> > the slider crosses
> > the deadband, the output jumps from one end of the
> scale to
> > the other,
> > depending upon the direction of rotation.
> 
> > Basically it's this: you have a knob with a disc of
> > polariser film on it's
> > shaft. The disc endlessly rotates, when the knob is
> turned.
> > Above the disc,
> > set at 90 degree angles, you have two Light Dependent
> > Resistors, (LDRs),
> > each which has another piece of polariser film over
> it, the
> > films aligning
> > to 90 degrees also. Under the disc are two LED's
> pointing
> > at the LDRs. When
> > the disc rotates, the effect of the crossing and
> uncrossing
> > of the polariser
> > films is to vary the light falling on the cells, in a
> > roughly sine/cosine
> > fashion. This means the voltages derived from the
> cells go
> > smoothly from min
> > to max and down again as the disc rotates, and there
> is no
> > sudden jump at
> > the dead-band as there would be with an endless pot.
> 
> I had the idea of 360 deg pot cabon/plastic just the
> regular
> P160 model design where at 90deg one had a tap/leg out of 0
> ohm
> and at 270deg a tap/leg of e.g 10Kohm, and the regular
> circular
> center tap. E.g apply AG at 90deg and +5V DC at 270deg and
> 
> variable DC at center tap. So one gets two sides with
> equal
> value and no jumping and no dead zone but only a variable
> range of 180deg. Full rectified sinus pot!
> 
> Reg
> KD
> 
> 
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