He reads a voltage from a 555 timer using the ADC on the microcontroller. At first glance it may not seem like a great source of randomness, but he performed some testing and the results look ...

If they use an Arduino, it should have been an ATtiny. And of course, if an ATtiny was used, there should have simply been a 555 timer. This time, however, [Tim] decided to actually show how this ...