USB Hourglass with Sand Timer Controlled By Arduino

Overview

This project combines a sand timer with a rotating mechanism and an optical beam through the center of the timer to observe the falling sand as they create a USB Hourglass.

Details

A microcontroller is used to determine when to rotate the hourglass and processes the amount of light reaching a detector that is digitized at frequent intervals. The digitized light levels can be used as a source of random entropy by sending them through USB to a host PC while the USB cable supplies the power. The user can look at the sand falling through the center of the hourglass and monitor the randomness in the USB output data with the USB Hourglass. The mechanical mount for the timer is the prototype board.

The rotation of the USB Hourglass takes about 2secs and it runs about 2mins before it is rotated while the data is continuously produced. The raw analog-to-digital converter readings are outputted by the USB Hourglass as 10-bit non-negative integers in text form at 100 samples per second. The hourglass produces 900 bits/second of true randomness using a conservative estimate of 9 bits of entropy per 10-bit sample.