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2011.04 Optical Hard Drive Shutter

An optical shutter made from an ordinary computer hard drive. The mechanical and electronic driver designs are based on designs by the Atom Optics group at the University of Melbourne, Australia. The idea is simple - take a hard drive, brake it open and take control of its coil-driven read-out arm.

The electronic driver circuit is controlled by TTL pulses and generates a short pulse of high current followed by a much lower “steady state” current - see figures below for examples. The short pulse quickly accelerates the arm and the steady state current keeps it moving. The low steady current reduces the impact speed at the end positions and thereby also the resulting mechanical vibrations. A better vibrational isolation may be achieved using a vibration isolated mount.

The maximum speed of the driver circuit is just above 25 Hz (50/50 duty) where the LMD18200 IC delivers maximal current (3 A) at the peak of the pulse. Running it faster introduces fast oscillations in the driver output signal.

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Performance