Computer-Controlled Hourglass
The USB Hourglass combines a sand timer with a rotating mechanism and an optical beam through the center of the timer to observe the falling sand. The amount of light reaching a detector is digitized at frequent intervals and processed by a microcontroller to determine when to rotate the hourglass.
The digitized light levels are also sent by USB to a host PC where they can be used as a source of random entropy. Power is supplied over the USB cable.
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