Homemade (IE cheap!) galvos:

  Glue a front surface mirror (a broken fax machine has lots of this)
onto the top flat of a plastic bottle cap from coke etc.  Wrap 30-50
turns of #30 magnet wire (RS has this) around the cap near the upper
flat surface, so it's about inline with the mirror looking edge on.
Push a needle through the cap just below the mirror so the needle is
running just below the flat surface/mirror so the needle becomes your
axis.  (Actually, do the needle before the wire.)  I forget what to use
as the bearing for the needle points but you should be able to get it
from here.  Use a strong magnet on either side for the field and apply
voltage to the coil.  Voila, a galvo for a few bucks or less, vs. $100+
for anything commercial.
  Of course this is on the net somewhere, just don't have the URL handy.

Alan


Tim Kerby wrote:
>
> Hi
> I think by this tou are meaning galvanometers.  They cost more than servos
> to get decent ones and I am not planning any serious shows with the
> equipment.  As I said before, it is mainly a demo of computer control of
> the beam.  By using servos, I can turn the project into something else when
> I am finished.  As for raster and other scanning methods, it is way too
> complex for a short project.  I saw the tomorrows world program a while
> ago.  They projected a flower didn't they?
>
> Tim Kerby
>
> At 10:51 12/12/97 +0000, you wrote:
> >I believe that for the kind of thing you describe, the lasers are
> deflected by
> > cunning gadgets.
> >
> >You know how a simple ammeter works: they're like that except the needle is
> > replaced by a tiny mirror.
> >The laser shines at a mirror, and angular deflection is proportional to
> current.
> >The light beam becomes a very long zero-mass needle!
> >You still have the inertia of the coil and mirror, but this is still a lot
> > faster and simpler than steppers
> >
> >You use a pair to scan in x and y directions.
> >
> >What kind of show did you have in mind?
> >The arrangement above can generate nice Lissajous figures.
> >
> >If you want to do some kind of raster scanning, then typically you'd use a
> > rotating octagonal mirror to do the
> >repetitive sweeps. Tomorrow's World showed this principle with a mix of red
> > green and blue lasers to produce a
> >cinema type of display. Always focused too.
> >
> >
>
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