Recently I got a lot of people writing me their soldering iron controller kinda work, but doesn’t heat up. One of the other symptons is that — ZzZZZ — is displayed on the OLED. However this is a feature of the controller, but the documentation is a bit vague about that. Documentation will be updated shortly.
The controller has a small 3×2 .1″ header in the topleft corner. 2 Pins are GND, 2 pins are VCC (+3v3), the other 2 are to detect if the tip is connected (!TP) or if it is placed in the stand/powerdown mode is needed (!PD). Grounding the tip detect pin will get the device out of sleep and will immediately start heating the tip. The powerdown pin will set the tip temperature after a few seconds to about 150 degrees and keeps your iron hot standby 😀
To fix this ‘problem’ short !TP and GND with a jumper.