Re: CD drive electronics question...

alanganes@xxxxxxxxx wrote:

Hi all,
While disassembling a junk CD drive the other day, it occured to me
that
inside here is a very precise linear positioning system. if one were to
combine 2 of them you could have a small range but very precise X-Y
positioning stage, maybe useful for some really cool stuff, or just for
the heck of it. Looking at the one I have, there is a rack and pinion
setup the moves the head back and forth, driven by a small DC motor
through some anti-backlash plastic gears. The motor dirves a gear that
has a ring of magnetic material attached around its periphary, that
hangs over a tiny PCB with two small 4 pin SMT devices the are just
below the magnet ring. I am guessing that these are some sort of hall
efffect sensors that are used for position feedback to control the
motor, and thus the linear position. For even finer control, one could
actuate the voice coils that move the optical head back and forth and
up and down.

I would like to be able to "manually" position (with a pot or
whatever) the head via the motor that drives the rack and pinion, and
then tweak it with the voice coils. In a few (very) limited experiments
I am able to move the head via the voice coils by applying voltage to
the appropriate points.

Now I am not near smart enough to be the first one to have thought of
this. Anyone know of anybody doing this already? I would like to play
with such a system, but don't really want to "re-invent the wheel". If
anyone has seen anyrhing like this, please point me in the right
direction. A google search has not turned up much, but I may not be
picking my search terms well, either. Could you do this in software
using the existing hardware? I am not a s/w guy, so I would appreciate
some opinions as to wether that is a stupid approach or not.
Anyone know of a place where one could find schematics for one of these
things? Any ideas or comments?

Thanks for any advice!

AL A.

A suggestion, since much of the technologies in making CD's work was
patented, you might try looking through www.uspto.gov patents with the key
words "compact disk".

--
JosephKK
Gegen dummheit kampfen die Gotter Selbst, vergebens.  
--Schiller
.

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