If you don't mind long latency, and you can ensure a clean environment,
then stacks may be a good solution.  Each stack requires either once
center rod, or three edge rods.  The robot can be in the center of a
circle of stacks, with one 'stack space' taken up by one or more reader
devices.

If you use a 3 foot square area then you should be able to manage 16
stacks, with each stack holding about 30 discs.  If it takes 5 seconds
to pick a disc up and move it to any other stack or to a reader then
your average latency for any disc should be under 1.5 minutes.  For
music jukebox it isn't an issue if you have two readers since you can
pick up the next play disc while the current one plays.

Optimizations would include algorithm enhancments so the 'maintenance'
of the stacks is tailored to favor more frequently accessed items, or
items in which the latency is an issue (DVDs near top so that selection
to play time is under a minute).  Another option is to double stack the
stacks - have two or more levels of stacks.  The robotics becomes a bit
more involved, and there must be a pass-through spot for the robot (ie,
one or more missing stacks so the robot can move between levels).  Since
the stacks would be small, you could easily fit 2-4 levels of 16 stacks
each into a 3' cube.

Of course, this, and most other solutions, would take so much time and
money that you may as well buy a cheap computer, and throw $600 worth of
drives into it for a total storage capacity of 1 TB (where TB = 1x10^4,
not 1x2^10^4).

1 TB will hold at least 100 DVDs, or well over 1500 CDs.  (350CDs and
75DVDs simultaneously)  The system would take up the space of a full
tower, and consume more power than the robotic system, but it would be
more reliable, faster, and less fiddly.  It could be placed anywhere
with a network connection and either the audio/video can be routed, or
you can place a silent computer on the network elsewhere to read the
audio/video off the server.  You also wouldn't risk a malfunction or
breakdown which may damage or destroy discs which are not cheap to replace.

-Adam

Koen van Leeuwen wrote:

>Hi all,
>
>I'm brainstorming for my next (hobby) project, an automatic CDROM-changer for
>my entire CD collection, total ~450 CD/CDROM/DVDs. In these quantities it is
>mostly called a jukebox. I was thinking of a PIC controlling the robotics,
>interfaced via RS232 to my computer, and an external disk drive.
>But I can't find a way to pack the cd's efficiently (the main reason to do
>this) and pick them up in a non-complicated manner.
>In professional jukeboxes, all CD's are in small trays but I don't like the
>idea to make 500 complicated trays myself.
>Do any of you have a good idea?
>
>Thanks in advance,
>
>Koen van Leeuwen
>
>--
>http://www.piclist.com hint: To leave the PICList
>mailto:piclist-unsubscribe-request@mitvma.mit.edu
>
>
>
>
>

--
http://www.piclist.com hint: To leave the PICList
mailto:piclist-unsubscribe-request@mitvma.mit.edu