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AxxAxx/AxxSolder
STM32 Based soldering station for JBC cartridges, 9-24 VDC and USB-PD power
AxxSolder is a DIY soldering station controller for JBC C115, C210 and C245 cartridges, built on an STM32G431 with a 9-24 V DC or USB-PD input and a TFT display. It is aimed at hobbyists who are willing to fabricate the PCB, flash firmware over SWD, and take on the electrical risks of grounded tips.
- JBC cartridges share the same two wires for heater and thermocouple, so the firmware alternates between heating and measuring: the heater is cut for 0.5 ms before each ADC sample, 40 times a second. The README backs this up with scope captures, which is more useful than a prose description.
- The high-side MOSFET with a bootstrap gate driver is a sound choice for this problem. The README explains why a low-side switch would float the thermocouple to the rail whenever the MOSFET is off, which is the moment the measurement has to happen.
- The PID has concrete anti-windup handling: conditional integration above a 75 °C error, a separate integral clamp, a larger integral gain for negative errors to deal with passive cooling, and derivative on measurement. The tuning constants are published with the reasoning behind them.
- Handle identification depends on jumper wires inside the connector, and the README admits that some JBC clones are bridged differently. A wrong bridge selects the wrong calibration polynomial and power limit, which the README says can damage a cartridge. The safeguard is a manual check, not something the firmware verifies.
- Temperature accuracy depends on four fitted polynomials from a few specific cartridges, plus a six-point user offset. Anyone with a different cartridge needs an external reference thermometer such as a Hakko FG-100 to get calibrated readings.
- The grounded-tip safety case rests on the builder choosing the right supply. The README warns clearly about PELV supplies and USB-C shells tied to mains earth, but a mistake there can short the tip through the handle, and the repo cannot enforce it.
- The NT115 detection path means cutting into the PCB of a JBC ADS stand, and the README does not describe any testing beyond a CI build badge. Users have to trust their own bench checks before applying full power.