[sdiy] Telharmonium motors, perhaps?

[James Patchell]

These days, it is posible to get approx 800,000 cycles onto a 2 inch size 
disk, although, encoders like that are not cheap.

They use a diffraction property to get the sin/cos signal.

http://www.microesys.com/graphics/M2Images/optical-clock.jpg

http://www.microesys.com/


At 02:23 PM 11/23/2004 +1100, Ken Stone wrote:
>Personally, I don't think a single disk could be used successfully - there
>would either be too many inacuracies, or too fine a resolution on the disk
>for easy manufacture. Early Compton units did it with two rotors, according
>to one web site, and they later went for twelve separate rotors anyway. Note
>however, they
>use a single motor with the twelve rotors  - it is the diameter or the
>rotors that they vary.
>
>As for using one as a VCO, the flywheel effect was too great on the one I
>played with, though a really enthusiastic person may consider adding brakes
>(mechanical or by shorting the motor) to encourange quicker speed reduction,
>and whopping great surges to rapidly speed it up.
>
>Have fun!
>
>Ken
>
> >A TOG (top octave generator) can derive 12 pitches from one master
> >frequency, so I say that yes, one rotating disk could contain 12
> >optical pitch tracks, BUT... the numbers are not very encouraging.
> >Remember that we need high frequencies (we must accomodate the *top*
> >octave, after all). A turntable is way too slow.
> >
> >Take a look at the TOG divisor ratios:
> >    http://www.organservice.com/crm/topdividers.htm#Fig6
> >
> >Visualize a protractor and you can picture 360 divisions per circle.
> >One revolution = 1 cycle.
> >
> >Enough rambling for now...
> >--
> >john
> >
> >
> >----- Original Message -----
> >From: "Glen" <mclilith at charter.net>
> >To: "Michael Baxter" <mab at cruzio.com>; "Gene Stopp" <gene at ixiacom.com>
> >Cc: <synth-diy at dropmix.xs4all.nl>
> >Sent: Monday, November 22, 2004 8:46 PM
> >Subject: RE: [sdiy] Telharmonium motors, perhaps?
> >
> >
> >> At 08:09 PM 11/22/04 , Michael Baxter wrote:
> >>
> >> >This then leads to a motor speed controller and phase-locked loop,
> >and
> >> >then eventually 12 motorized speed controllers for an
> >equal-tempered
> >> >octave, with 12-16 VCAs per voice ...
> >>
> >> I wonder if you would really have to use 12 motors? Perhaps you
> >could get
> >> more than one of the 12 notes of the scale on the same disk? If the
> >disk is
> >> larger, it would be easier to fit more notes on it. If you use
> >opaque
> >> printing with reflective sensors, you can also use printing on both
> >sides
> >> of the disc. If you could manage to cram all 12 notes of the scale
> >onto one
> >> disc, you would automatically guarantee that the unit would always
> >be in
> >> tune with itself, without the need of servos or PLLs. I wonder if a
> >special
> >> disc could be printed and adapted for a common vinyl record
> >turntable?  :)
> >>
> >> It would certainly be a cheap way to experiment with the concept,
> >and it
> >> might be of some research value, even if you eventually decide to do
> >> something far more elaborate.
> >>
> >>
> >> take care,
> >> Glen
> >
> >
>_______________________________________________________________________
>Ken Stone   sasami at hotkey.net.au or sasami at cgs.synth.net
>Modular Synth PCBs for sale <http://www.blaze.net.au/~sasami/synth/>
>Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>

         -Jim
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