Americium from a smoke detector and a G-M tube
You might be interested in this recent discussion:http://arduino.cc/forum/index.php/topic,108380.0.html
The legality of that method seems rather questionable to me..
QuoteThe legality of that method seems rather questionable to me.. Can't think of a good reason why it should be, unless dismantling a smoke detector is in some way illegal.
It only produces about 8 bytes per seconds, but if you need more it can be used to seed a pseudo-random generator, either the one built into the arduino library
or perhaps one of the better ones such as blub-blub...
I suppose, while we're on the topic of noise, one could use the noise produced by a broken component that still erratically conducts? Such as a capacitor that's undergone dielectric breakdown, or a diode that's avalanched one too many times?
A good random firing cell I made in the 60s, consisted of a small tube with some cotton wool soaked in Silver Nitrate solution.