[Doug] pulls a signal from the 9V AC power before it hits the bridge rectifier, using a 100K resistor and a zener diode to protect the microcontroller pin. The code for that project comes as a hex ...

Using N-Channel MOSFETs to switch AC, sensing temperature changes with signal diodes, and even replacing a 555 with a blinking LED are just a few of the hacks covered in the video below the break.