70W soldering iron controller
smdprutser.nl build a soldering iron controller based on PIC16F1823:
In series thermocouple soldering iron have a thermocouple in series with their heating element and thus only have two connections (actually one more which is electrically connected to the tip for ESD purposes). When a voltage is applied to the two terminals the tip heats, when unpowered the thermocouple voltage can be read.
70W soldering iron controller – [Link]