Carousel 5 – Studless

This Lego Mindstorms NXT robot uses two synchronised
motors to power the large outer ring (the outer ring 
is from Lego Set 4481 Star Wars Hailfire Droid), this 
in turn rotates the four turntables. 

A light sensor checks the position of one of the
platforms that carry the marble cups, the turntables 
are rotated a fixed distance from the light sensor to 
be in the correct position for the reciprocating heads 
to pick or drop a marble as appropriate. The platforms
are then rotated again into position for the next marble.

A third motor powers the reciprocating heads. A light 
sensor is used to detect a 360 degree rotation.

See the Video:
http://video.google.co.uk/videoplay?docid=-5059369289912512581