As part of a larger project, Instructables user "thejuggler" has created some very large animatronic tentacles. Each tentacle uses servos that pull speedometer cables to create movement in the tentacle, which is custom made from laser-cut parts. The servos are controlled by a NIntendo Wii nunchuk interfaced to an Arduino board. Although the project is still a work-in-progress, the following video shows a tentacle in action:
Considering something like this would have been outside the scope of the ordinary hobbyist a few years ago - it's a great project. For more information and design files, visit the project page.
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