Frank Zhao built two working induction soldering irons from scratch, documenting the full designs at eleccelerator.com. Induction irons outperform resistive irons of identical wattage because they heat the tip directly via an internal coil, eliminating the lag of a distant heater cartridge. Temperature regulation requires no sensors or electronics: the tip self-regulates at the cartridge material's Curie point, where heating efficiency collapses. That simplicity shifts all real complexity into the power supply.
Zhao's first design updates SergeyMax's reverse-engineered Metcal circuit with parts available in the US. It runs at 13.56 MHz through an F-type connector, making it compatible with Hakko and Metcal handpiece assemblies off the shelf. It accepts both XT30 and USB-PD power inputs and fits in a 3D-printed enclosure. His second design derives from the open-source RadioThermal project, runs at 470 kHz, adds XT30 and USB-PD support, external jumper-based power selection, and fuse protection, and uses a custom handpiece built around a standard commercial tip.
Read the full writeup for the circuit-level detail on the RF power stage, the specific component substitutions that made the first design viable outside Russia, and the handpiece construction on the lower-cost 470 kHz unit. This is worth your time if you care about how tip geometry, coil design, and operating frequency interact, not just the finished result.
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