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From: cgordon@vpnet.chi.il.us (Gordon Hlavenka)
Newsgroups: sci.electronics
Subject: Kludged Laser Power Supply
Message-ID: <2667547f-214.1sci.electronics-1@vpnet.chi.il.us>
Date: 2 Jun 90 05:55:06 GMT
References: <5395@jhunix.HCF.JHU.EDU>
Lines: 29



>Now all I need are two galvometers...


No, it works well with an old speaker.  The trick is to glue a mirror onto
the voice coil, but just a bit off center.  You also want some "slop" in the
mounting.  I find RTV works very well.  When you play sound into the
speaker, you get wonderful patterns.

For more precision, remove most of the speaker cone and mount the mirror
firmly onto a rigid stick which pivots on the rim of the speaker frame. 
This gives _mostly_ linear response.  With two of these and some playing,
you can do circles.  With LOTS of work you can do small amounts of text or
simple line art.  But I mean _small_ amounts and _simple_.

There are companies that sell positioners for laser drawing.  With these you
could build a laser TV projection system or something...  But that's
probably out of your price range for a $30 laser.

Interesting app:
A friend has a 4-acre lot, and often has unauthorized hunters on the
property.  He bounces the beam around two corners to cover 3 sides of the
lot.  When the beam is broken loudspeakers in the brush tell the hunters to
get lost.  Of course he has to keep the brush trimmed back, the mirrors get
knocked around / dirty, and he warns off a LOT of animals.  But it's fun to
play with, and that's the whole point after all...

Gordon S. Hlavenka            cgordon@vpnet.chi.il.us
DISCLAIMER: He's lying.