[sdiy] Tonewheel questions

[fmg]

With a bit of patience (and a stable pair of hands) it could be made in
a broken hard disk. The 3-phase disk motor driver IC never blow (almost)
It should be a matter of time and a good pair of eyes to locate which
pcb traces to cut and which to pull up to keep it turned ON all the time.
I think the older the HD the better (more ICs - separated tasks, as
those 20...40MB ones).

I think that 12 sensors shouldn't be a problem once the heads were
removed. An X structure over the disk could house them, 3 by segment. Or
3 groups of 4 long screws with the sensors on them attached to the HD
sides (tracking would be a matter of turning screws).

For the drawn pattern... well well... I wouldn't do it, for sure.
That's a job for a vector drawing software and a good printer.

What follows is a small list of (possibly) other peripheral to
experiment with:

5 1/4 and 3 1/2 FDDs:
Good: Motor driver easy to hack. Steeper motors (reacts fast to speed
changes even for starts/stops). Easy to mod for CV ("motorized" VCOs).
Bad: Too low rpms for a TOG. Hard to work (specially for 12 sensors -
perforated disks? )

CD drives:
Good: Motor driver easy to hack. Good rpms for a TOG. Spacious to work.
Bad: Very fragile. Last less than the overall project. Very fragile.
Electronics dies at 70...90% of the project. Machanics dies at 30%
Did I said before they're very fragile?

Printers (platen part):
Good: The platen is big enough for a lot of weird experiments.
Sensors could act as synchros for free running VCOs (to stablish the TOG
frequency-relationship rules periodically, or alter them dramatically).
Multiphase multiwaveforms LFO. Steeper motors reacts fast enough to
speed changes, start/stops, change in direction. Motors drivers can be
made to accept CVs (vibrato, LFO)
Bad: Too low rpms for a directly usable oscillator (except for a LFO).
The built-in electronics (except PS) is generally useless. Motor
drivers and logic have to be made from scratch.


Fabio


Harry Bissell Jr wrote:
> 
> My method would be to use retro-reflective optical
> sensors on a 12" diameter cardboard disk carried on
> a turntable platter.  speed control would be
> excellent.
> You could use white cardboard and black magic marker.
> Different frequencies could occupy different positions
> on the disk
> 
> H^) harry  (remember- the name "plastic
> scratch-o-graph"
> is my trademark :^)
> 
> --- Ingo Debus <debus at cityweb.de> wrote:
> >
> > Am Freitag, 28.05.04 um 10:43 Uhr schrieb Ken Stone:
> >
> > > For a simple way to experiment, take a look at old
> > video players. In a
> > > lot
> > > of them you will find some kind of feedback
> > mechanism on the capstan
> > > motor
> > > or video drum motor. These sometimes take the
> > physical structure of a
> > > tone
> > > wheel.
> > >
> >
> > That's a great idea. I once ripped a video drum
> > (that thing the
> > rotating heads are mounted on) apart, and it
> > contained a ring shaped
> > magnet. This magnet was polarized in a way that
> > there were many north-
> > and south-poles around its circumference. This would
> > make a tonewheel
> > that is already magnetized, you just could use a
> > coil as pickup. Hmmm,
> > there were even some coils already in it, these and
> > the magnet were the
> > motor.
> >
> > Ingo (imagining a tone wheel generator made of 96
> > video drums)
> >

-- 
Fabio Gonzalez
Posadas, Argentina