I designed this arm for a DIY Useless Machine. The useless machine is a simple box with a switch and motor, when you turn on the switch the lid opens and the arm swings out and turns off the machine and then retracts. It is so simple but brings a smile to the face of everyone that tries it. The Useless Machine was not created by me, it can be found in Make Magazine and in numerous instructables.

You can find the youtube video here showing the complete device! http://www.youtube.com/watch?v=kWip--0hRCI&feature=youtu.be