Overview

Gem Solder is an STM32-powered soldering iron controller for general-purpose C245 tips. It runs from a PD-compatible USB-C power source or from a DC power source of up to 24V, including 3S–6S battery packs. USB-C power delivery negotiates up to 20V.

Features

• Compact, DIY-friendly, two-layer 80×34 mm PCB.
• Current sensing feature measures the heater element's resistance to derive an accurate power estimate, so the iron works correctly with aftermarket tips whose resistance differs from the 2.4Ω of a genuine C245 tip.
• Resting the metal ring of the handle on a metal plate pulls the stand-sense input low and drops the iron to the sleep temperature, slowing tip oxidation. A quick tap on the plate toggles sleep when Tap to sleep is enabled in the settings menu.
• An adjustable timeout setting returns the iron to the home screen and lets the tip cool down if it stays in sleep mode for too long.
• RGB status LED colour by mode:
• 🟩 green - standby
• 🟥 red pulse - heating
• 🟥 red static - at setpoint
• 🟦 cyan pulse - cooling, still hot
• 🟪 violet - sleeping
• Once the DFU bootloader has been flashed to the device, all later firmware updates can be done over a USB data cable.
• PID temperature control, adjustable power limit, power pulse to keep power banks awake and more from IronOS.
• PD debug menu to read the power source capabilities.
• USB-C PD and an XT60 connector make it workable from a power bank or battery pack, for soldering away from the workbench.
• 20 kHz heater PWM keeps the switching noise of the high-current drive above the audible range.