This project has been mostly superseded by a more portable random number generator.
The world's first portable, handheld, electronic, truly random number generator. No more messy and possibly biased dice or coins. Useful for consumers who have trouble making choices.
Noise -- which is supposedly as random as can be -- is generated by a reverse biased diode (in this case the diode is 2/3 of a transistor) and then converted to a TTL level digital signal. The upper end of the output range is set through the buttons on the front and displayed on the bottom line of the LCD. For simplicity, the lower end is always zero.
The noise source is biased so Von Newmann's methodis used. Bits arelooked at in pairs. If they are the same, the bits are discarded. Ifthey are different the second bit is used. Taking in N random bits willresult in a number between zero and 2^N-1. Two numbers between zero and2^N-1 -- where N is the smallest value such that 2^N-1 is beyond theupper end of the output range -- are generated. For kicks, these twonumbers are then XORed together. If the resulting number is outside ofthe desired range, it is discarded and the process is repeated.
Eventually, we end up with a random number in the range we want. It is then converted from binary to binary coded decimal and outputted on the first line of LCD.
Click on the schematic for a larger version.
