[sdiy] Telharmonium motors, perhaps?

[Michael Baxter]

Well ... decided watching the traffic go by that there's another excellent
way to approach this problem in the SDIY context ...

1. Print tone wheel with laser or ink jet printer onto a CD label.

2. Paste label onto a garbage or blank CD.

3. Hack a cheap CD player to act as the mechantronics.

4. (Per this post) Use photo transistor array for pickup of transitions or 
waveforms.

5. Augmentation of idea: use COLOR inks and COLOR LED illumination, and 
COLOR filters to change transfer functions of printed disk for tone 
production. Allows a kind of spatial compression to pack in more sound per 
disk, possibly with the subtractive inks overlaying each other.

6. Second augmentation -- have several possible CDs to use as application 
specific tone wheels.

"It's almost too easy..."

Arghh!

Best,
Michael

On Tue, 23 Nov 2004, Tim Parkhurst wrote:

> > -----Original Message-----
> > From: john mahoney [mailto:jmahoney at gate.net]
> > Sent: Tuesday, November 23, 2004 3:17 PM
> > To: Gene Stopp; synth-diy at dropmix.xs4all.nl
> > Subject: Re: [sdiy] Telharmonium motors, perhaps?
> > 
> > From: "Gene Stopp" <gene at ixiacom.com>
> > 
> > > Random thoughts which keep popping into my head despite my attempts
> > > to suppress them...
> > >
> > > Smaller motor = less portamento?
> > 
> > Maybe. The ratio of torque to rotational mass seems pretty important.
> > 
> 
> What you want to do is reduce the rotational inertia. Ideally, you would
> make the motor as small in diameter as possible, but longer to increase the
> magnet / rotor area. There are "low inertia" servo and stepper motors which
> are designed like this (remember the spinning figure skater with her arms
> pulled in... =lower polar moment of inertia).
> 
> > 
> > > Tone wheel idea - metal disk with "waveform" around the edge, again the
> > > smaller the better for inertial reasons?
> > 
> > Smaller = less precision.
> > 
> > > Disk can be made with Dremel tool - any accidental (or intentional)
> > > asymmetry would be a subharmonic?
> > 
> > You'll get "wow" (subharmonics), flutter, and jitter, I think.
> > 
> 
> I would have to think that an optical approach would be much superior.
> Printing the disks on a laser printer should be a snap, and the response
> time of a good opto sensor (i.e. a phototransistor) would be much better.
> Nice sharp transitions would be a breeze. 
> 
> 
> > > Optical disk may have less weight, less momentum, sharper possible
> waveform
> > > edges?
> > 
> > I guess "yes."
> >
> 
> I second that emotion...
>  
> > 
> > I favor the polyphonic approach, in theory, especially with such small
> > motors. Cherish the minor tuning imperfections!
> > --
> > john
> >
> 
> I think this could be a really fun little project. We can all thank (or
> blame) John M for finding these motors...
> 
> 
> Tim (less momentum, sharper edges) Servo
> 
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