Despite not being inherently any better at converting electricity into heat, induction-heated soldering irons often considerably outperform conventional irons with an identical power rating. They manage this by directly heating the iron tip with an internal induction coil, rather than conducting heat from a heater cartridge farther back — a design which makes induction irons very responsive, stable, and, unfortunately, expensive. [Frank Zhao], though, managed to design and build two induction soldering irons of his own.
In some ways, the handpiece of an induction-heated soldering iron is simpler than a resistive iron. Induction-powered soldering irons don’t have temperature sensors or any kind of electronic temperature control. Instead, the tip’s temperature is set by the cartridge material’s Curie point; once the cartridge reaches this temperature, the heating efficiency drops off sharply. This self-regulation means that most of the project’s complexity is contained in the power supply, which supplies an RF signal to the induction coil.
Here, [Frank] had two previous projects to work off of, and he based one design on each. The first was the work of [SergeyMax], who’d reverse-engineered a Metcal soldering iron and built his own induction iron based on it. This relied, however, on components hard to find outside of Russia, so [Frank] updated it to use parts available in America. It uses a frequency of 13.56 MHz and an F-type connector, making it compatible with the handpiece assemblies from a number of commercial manufacturers, including Hakko and Metcal. For a measure of portability, it can be powered through an XT30 connector or USB-PD and fits in a compact case.
[Frank]’s second, more inexpensive design was based on the open-source RadioThermal project, but adds the same XT30 and USB-PD power options, allows power level selection with external jumpers, and protects the circuit with a fuse. This design operates at 470 kHz, and uses a custom-built handpiece designed around a commercial soldering iron tip.
We’ve seen induction irons here before, albeit in a considerably less polished form. Alternatively, if you’re interested in seeing what’s inside a normal soldering iron tip, check out this teardown of a T12 tip.
