After trying out the TS100 portable soldering iron, hacker “Electronoobs” decided to build his own PCB-based version. It appears to be slightly larger than the TS100, but also quite functional, with a 3D-printed case and an OLED display. User interface is provided by a pair of buttons just like the original.
To keep the temperature at the proper range, a type K thermocouple inside the iron tip is read by a MAX6675 amplifier IC, which passes temperature data along to an ATmega328P chip. This then regulates power to the heater using the onboard MOSFET under PID control.
More details on the project can be found in Electronoobs’ write-up.