Color-Changing Pens, LEDs

There are some clear plastic pens around, being given away as premiums, They contain Red, Green and Blue LEDs that slowly
turn ON and OFF, creating amazing color combinations.
What sort of LED controls can fit into such a small space?
Thanks for any help in finding out how this is done.
Bob snipped-for-privacy@yahoo.com
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Probably a PIC chip die under a droplet of epoxy.
Cheers!
Chip Shults My robotics, space and CGI web page - http://home.cfl.rr.com/aichip
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It's part of the LED itself, not a separate circuit. You can buy these LEDs "raw" for a dollar or two. All Electronics has them, as I recall, as do many others. They differ in the sequences, but they're all basically the same -- three colors that flash in different combinations. Popular in the rave world as belly-button ware, that sort of thing.
-- Gordon Robots for Less at Budget Robotics: http://www.budgetrobotics.com/ Author: Robot Builder's Sourcebook & Robot Builder's Bonanza
Bob wrote:

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