[sci.electronics] Laser show controllers?

mrapple@quack.sac.ca.us (Nick Sayer) (06/09/91)

Let's say I was crazy enough to want to design and build a lazer-show
controller.

It's obvious that you use a pair of mirrors - one to shift the beam
along the X axis, one to shift the beam along the Y axis. Fine.
But those shows achieve fast shifting around. So they must have
very fast, yet precise motors. Those motors aren't doing a raster
scan, they use vector graphics - hence the fine control. So it's
likely that a stepper motor would do the trick, perhaps something
along the lines of those used as cylindar select motors in hard
disks.

So now the $64 questions:

What sort of motors are capable of going that fast? Where can I get
them? How much do they cost?

-- 
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mcovingt@athena.cs.uga.edu (Michael A. Covington) (06/09/91)

How about moving the mirrors with a loudspeaker that has been modified
in some way, e.g., pinioned in a particular place so that you will get
angular rather than linear motion?

-- 
-------------------------------------------------------
Michael A. Covington | Artificial Intelligence Programs
The University of Georgia  |  Athens, GA 30602   U.S.A.
-------------------------------------------------------

gandrews@netcom.COM (Greg Andrews) (06/09/91)

In article <kWhnZkR@quack.sac.ca.us> mrapple@quack.sac.ca.us (Nick Sayer) writes:
>Let's say I was crazy enough to want to design and build a lazer-show
>controller.
>
>It's obvious that you use a pair of mirrors - one to shift the beam
>along the X axis, one to shift the beam along the Y axis. Fine.
>But those shows achieve fast shifting around. So they must have
>very fast, yet precise motors. 
>

The REAL ones ($$$) use something my buddy calls "Analog Servomotors", 
which I think means "a beefed-up galvanometer".  The drive rotates a
shaft to turn the mirror.  It reduces parallax in the mirror's movement
over hinged-on-one-side techniques.

If you're not overly concerned with large amounts of deflection, then
you can use audio speakers (as another posting mentioned).  They are
reasonably linear through the central 10-20 degrees of deflection, and
are cheap enough that failed experiments won't break the budget.

Another possibility might be the head positioner mechanisms from hard disk
drives.  Obviously, voice coil types would be preferred over the stepper 
motor ones.  (Guess what technology the "voice coil" drive was borrowed 
from!)


-- 
 .------------------------------------------------------------------------.
 |  Greg Andrews   |       UUCP: {apple,amdahl,claris}!netcom!gandrews    |
 |                 |   Internet: gandrews@netcom.COM                      |
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smasters@gmuvax2.gmu.edu (Shawn Masters) (06/09/91)

	The method of using a speaker to drive a mirror position has
been refined into what is known as a voice coil.  You mount a mirror on
the end of the voice coil, so that when it's extended it has a different
angle of reflection.  This is used in many models of laser disk players
to position the beam on the disc(in fact I got my first x y laser
display unit from a friend that tore down a Dragons slayer(sp?) game).
Another source is the stepper mechanisms out of some hard drives.
	The problems you find is that the coil vibrates, and there is a
bit of jitter if it's making discrete motions(from point to point).  You
can get it to make really neat paterns when hooked up to sinusodial
source on both x and y, but these tend to be fairly easy on the coils,
unlike most animation by laser.
	The other problem is that I've never seen a voice coil fast
enough to draw a diagram that the eye would catch whole.  You can get
them to do circles, but I think that would die on something more
demanding like a square.

	Of course, what you mentioned about the speaker is great for
home stereo systems and certain types of music:-).

Shawn Masters
smasters@cns01.gmu.edu

digex@world.std.com (doug e humphrey) (06/09/91)

What you want are called Galvonometers (galvos for short) and 
where to get them is easy; the number one supplier for such 
things as affordable (sort of) galvos is   General Scanning 
located in Watertown MA.  Their cheapest is something like $330
or so, scans only one axis (you use two of these together to 
get X-Y) runs around 20khz I think (doing this from memory) 
and settling time depends on the setteled accuracy that 
you need.  

Motors do not do this kind of stuff well, and they are no the 
technology that is employed.  GS has the basic pattents of some 
special capacitive coupled techniques that allow for very low 
mass, fast reacting structures to move the mirror structure, and 
good control to make sure that you do not overshoot the position,
etc.

You are about to step off the edge into some pretty expensive 
hardware if you really want to get into this.  A good galvo and 
control setup for laser shows is around $10,000 to start, and 
more than that for something that you would do a "real" show 
with.  Note that this does not count the lasers!  Build your
own can save you some money, though what you build will not 
be up to the standards of the commercially produced gear in all 
likelyhood, but it takes a *lot* of time, and in the end there 
is just no such thing as building your own galvos that can 
perform to the point where they are usable in a laser show.

GS locks their dumpsters up, because they know that there are
people in the Boston area lurking around trying to get the old, broken, 
maybe out-of-spec galvos that they no doubt throw away.  Not for 
industrial spying, but because some of us can not afford to pop
real bucks for galvos for our lasers.

By the way, what are you going to do for lasers?  I might have a 
nice Spectra Argon for sale, pumps easily 100mw, I can give you plans
for a good power supply, or you could buy from MKW and pay some real 
money!

Good luck.

Doug Humphrey

grege@gold.gvg.tek.com (Greg Ebert) (06/10/91)

In article <kWhnZkR@quack.sac.ca.us> mrapple@quack.sac.ca.us (Nick Sayer) writes:
>Let's say I was crazy enough to want to design and build a lazer-show
>controller.
>
[...]

Some off-perpendicular mirrors mounted on several (inexpensive) DC motors
work great. You 'cascade' the motors so that the beam strikes 3 or 4
motors before projecting onto your wall. We used some smashed mirror
pieces (about 1/2" diameter). Get some pots so you can vary the motor speed.
For $10 at Radio Snack you can make a pretty good display. To mount the
mirrors, cut some 3/8" dowel, sloppily drill a hole through the center,
press onto motor shaft, and glue-on the mirror. Very easy.

The shapes resemble something made with a Spirograph (remember those ?) :
complex elliptical forms. Subtle changes in motor speed make vivid changes
in patterns. The smoothness and patterns are especially pleasing to the eye,
even more-so if you are a bit inebriated.

We also glued mirror fragments to speakers in an attempt to syncronize to
music, but the motion is too random.

(Optional) Pink Floyd backgound music, perhaps a few 6-packs....

bame@hpfcbig.SDE.HP.COM (Paul Bame) (06/11/91)

Meridith Instruments (a semi-surplus laser-supply company) often has
galvos for sale - check out the advertiser index in Radio Electronics
or Circuit Cellar Ink magazines.

			-Paul Bame
			bame@hubble.sde.hp.com	N0KCL

mzenier@polari.UUCP (Mark Zenier) (06/11/91)

In article <kWhnZkR@quack.sac.ca.us> mrapple@quack.sac.ca.us (Nick Sayer) writes:
>Let's say I was crazy enough to want to design and build a lazer-show
>controller.

See "Elektor Electronics USA" for May and June 1991.  

These magazines have a two part construction article on a laser
light show using mirror galvanometers.  

(Of course it's probably a different date for one of the other
editions of Elektor.)  Elektor Electronics is a european electronics 
magazine, and Elektor Electronics USA is a new edition published by 
the "Audio Amateur" and Old Colony Sound Lab folks.

The kit is from

ELV France
B. P. 40
F-57480 Sierck-les-Bains
FRANCE

Elektor Electronics USA
P. O. Box 876
Peterborough, New Hampshire 03458

Mark Zenier  markz@ssc.uucp  mzenier@polari.uucp

Mike_Diack@kcbbs.gen.nz (Mike Diack) (06/12/91)

How about the focus/tracking mechanism out of a CD player ? good 2 axis 
movement & very fast.

frankb@hpsad.HP.COM (Frank Ball) (06/12/91)

/ Mike_Diack@kcbbs.gen.nz (Mike Diack) /  1:23 pm  Jun 11, 1991 /
*How about the focus/tracking mechanism out of a CD player ? good 2 axis 
*movement & very fast.
----------
I bought an old laser disc player surplus for $70 (no there aren't any more).
It has a He Ne laser and X-Y deflection mirrors.  The mirrors were controlled
by a complex feedback loop, but that circuitry that is not usable (for anything
but the origional function as a laser disc player).  There were some polorizers,
splitters, and lenses that I ripped out.  The mirrors have voice coils on them
(8 ohms), and I was able to use the origional deflection amplifiers.  I can get
about 200 Hz (it's rolling off by this point) of bandwidth out of the mirrors.
It looks ok with music, more bandwidth would be nicer with some types of music,
it's plenty for other types.  The bandwidth is much to limited for any type
of fancy graphics displays.

Frank Ball   frankb@hpsad.HP.COM   pyramid!hplabs!hpsad!frankb

hbg6@citek.UUCP (John Schuch) (06/13/91)

In article <kWhnZkR@quack.sac.ca.us> mrapple@quack.sac.ca.us (Nick Sayer) writes:
>Let's say I was crazy enough to want to design and build a lazer-show
>controller.
>
>scan, they use vector graphics - hence the fine control. So it's
>likely that a stepper motor would do the trick, perhaps something

Nope, not fast enough.

>What sort of motors are capable of going that fast? Where can I get
>them? How much do they cost?

You are looking for galvomotors. They are basicly a high horse-power
meter movement. Meridith Instruments in Phoenix sells used ones for
about $75 each. ( quite cheap compared to new ones ). Email me
if you need the address. They also have a lot of neat used
laser stuff.

John

.....................................................................
Have fun, Play nice, Don't fight.                             OK Dad.
.....................................................................
John Schuch - Motorola Inc., Computer Systems Division (602)438-3008
All opinions expressed are mine and not Motorolas,        their loss.
.....................................................................

tedwards@aplcomm.JHUAPL.EDU (Edwards Thomas G S1A x8297) (06/15/91)

In article <12530@qisoff.phx.mcd.mot.com> hbg6@citek.UUCP (John Schuch) writes:
>In article <kWhnZkR@quack.sac.ca.us> mrapple@quack.sac.ca.us (Nick Sayer) writes:
>>Let's say I was crazy enough to want to design and build a lazer-show
>>controller.
>You are looking for galvomotors. They are basicly a high horse-power
>meter movement. Meridith Instruments in Phoenix sells used ones for

There is a book called _The Laser Cookbook_ which describes some circuits
for driving galvos (usually just a 741 driving a complimentary pair of
medium-power transistors).

For those of you designing a laser show, I reccommend the AD7226 quad
8-bit D/A converter.  It saves you from having to have a large number of
D/A chips, opamps, and latches since it has all of that built in.
(i.e. voltage mode D/A).

-Tom

miker@polari.UUCP (Mike Ranta) (06/15/91)

In article <1840048@hpsad.HP.COM> frankb@hpsad.HP.COM (Frank Ball) writes:
>I bought an old laser disc player surplus for $70 (no there aren't any more).
>It has a He Ne laser and X-Y deflection mirrors.  The mirrors were controlled

This is a new one to me.  Every CD player I've ever seen uses an infrared 
laser diode.  A HeNe laser would be large, expensive, hot and limited in
life.  Also, there are no real usable mirrors for the purposes of a light
show.  The laser diode, receiver diode, optics and focus/tracking servos
are usually all together in an assembly about .5" square!  The only other
component from a player is the positioning servo that moves the above
assembly along the disk.  It's MUCH to slow for this application.

rainer@boulder.Colorado.EDU (Rainer Malzbender) (06/17/91)

In article <4449@polari.UUCP> miker@polari.UUCP (Mike Ranta) writes:
>In article <1840048@hpsad.HP.COM> frankb@hpsad.HP.COM (Frank Ball) writes:
>>I bought an old laser disc player surplus for $70 (no there aren't any more).
>>It has a He Ne laser and X-Y deflection mirrors.  The mirrors were controlled
>
>This is a new one to me.  Every CD player I've ever seen uses an infrared 

Laser disc player doesn't mean CD player. A friend of mine used an old
laser disc player to make a 3D digitizer, and I'm fairly certain it also
had a HeNe and mirrors in it.

--
Rainer Malzbender 
Dept. of Physics (303)492-6829 
U. of Colorado, Boulder         rainer@boulder.colorado.edu 128.138.240.246

rainer@boulder.Colorado.EDU (Rainer Malzbender) (06/17/91)

In article <4449@polari.UUCP> miker@polari.UUCP (Mike Ranta) writes:
>In article <1840048@hpsad.HP.COM> frankb@hpsad.HP.COM (Frank Ball) writes:
>>I bought an old laser disc player surplus for $70 (no there aren't any more).
>>It has a He Ne laser and X-Y deflection mirrors.  The mirrors were controlled
>
>This is a new one to me.  Every CD player I've ever seen uses an infrared 
>laser diode.  A HeNe laser would be large, expensive, hot and limited in

Laser disc player doesn't mean CD player. A friend of mine used an old LDP
to make a 3D digitizer, and it also had a HeNe and scanning mirrors.

--
Rainer Malzbender 
Dept. of Physics (303)492-6829 
U. of Colorado, Boulder         rainer@boulder.colorado.edu 128.138.240.246

rainer@boulder.Colorado.EDU (Rainer Malzbender) (06/17/91)

Oops. Sorry about the duplicate, News on this machine is approaching senility.
Rainer Malzbender 
Dept. of Physics (303)492-6829 
U. of Colorado, Boulder         rainer@boulder.colorado.edu 128.138.240.246

andywang@power.berkeley.edu (Andy Wang) (06/24/91)

mrapple@quack.sac.ca.us (Nick Sayer) writes:

>Let's say I was crazy enough to want to design and build a lazer-show
>controller.

Silicon Valley Surplus has a "home laser light show" controller in their
~June catalog. In short, the features are: 

2 lissajous oscillators
2 galvos
20 deg vert swing, 180 deg horiz, 10 deg pattern
pattern rate 100hz
2 audio inputs
computer (parallel port) interface with D/A converters

No laser included
Medium-difficult assembly

$99.00

They also have a bunch of other cool stuff, especially stepper motors.

The address is:
1273 Industrial Parkway W.  Bldg. 460
Hayward, CA 94544

Andrew
andywang@power.berkeley.edu