Two 3D-printed enclosures, one blue and one red, sit on a workmat. In front of the blue enclosure, a soldering iron sits in a blue-and-yellow soldering iron stand.

Building A Homemade Induction Soldering Iron

November 7, 2026 by Aaron Beckendorf 2 Comments

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.

Magnetic Induction Heats Water

May 1, 2026 by Bryan Cockfield 51 Comments

Producing hot water off-grid is a surprisingly energy-intensive activity, and although it looks simple on its surface it can get quite complicated especially when used in large scale for something like providing hot water for an entire home. When using combustion to heat the water there needs to be proper venting as well as control of the fuel, and even storage of the hot water needs to be meticulous to avoid certain pathogens. [Greenhill Forge] has built an off-grid solution for heating hot water that doesn’t necessarily rely on any combustion, though, provided he can find something to spin his custom electric machine.

The machine in question is, of course, an induction heater. It works similar to any simple electric motor, generator, or transformer except in this case the eddy currents generated are exploited rather than minimized. Normally these currents, generated when a magnet passes by a metal, are wasted heat in other machines but in this induction heater it’s the goal. The machine’s stator is built from copper tube wound in a spiral which allows water to flow through and absorb heat. The tube is soldered into one electrically solid mass to maximize the eddy currents. The rotor is taken from a previous generator built by [Greenhill Forge] which holds the permanent magnets.

During the initial tests using a power drill to drive the generator, he was able to heat 1.5 liters of water from 7.9C to about 24.4 C in three minutes. The math works out to providing 575 watts of power to the heater, and with something that could spin the generator faster it might have the potential to provide around 14.5 kW. Provided that there’s a source of energy around, such as a wind or water turbine, this could be a fairly sustainable way of generating hot water in off-grid situations. Some of [Greenhill Forge]’s other projects are centered around this idea as well, like one of his builds which uses waste sawdust to heat his workshop with a custom-built stove.

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AC Motor Converted Into DC EBike Powerplant

January 15, 2026 by Bryan Cockfield 12 Comments

AC induction motors are everywhere, from ceiling fans to vehicles. They’re reliable, simple, and rugged — but there are some disadvantages. It’s difficult to control the speed without complex electronics, and precisely placing the shaft at a given angle is next to impossible. But the core of these common induction machines can be modified and rewired into brushless DC (BLDC) motors, provided you have a few tools on hand as [Austin] demonstrates.

To convert an AC induction motor to a brushless DC electric motor (BLDC), the stator needs to be completely rewired. It also needs a number of poles proportional to the number of phases of the BLDC controller, and in this case the 24-pole motor could accommodate the three phases. [Austin] removed the original stator windings and hand-wound his own in a 16-pole configuration. The rotor needs modification as well, so he turned the rotor on a lathe and then added a set of permanent magnets secured to the rotor with JB Weld. From there it just needs some hall effect sensors, a motor controller and power to get spinning.

At this point the motor could be used for anything a BLDC motor would be used. For this project, [Austin] is putting it on a bicycle. A 3D printed pulley mounts to the fixed gear on the rear wheel, and a motor controller, battery, and some tensioners are all that is left to get this bike under power. His tests show it comfortably drawing around 1.3 kW so you may want to limit this if you’re in Europe but other than that it works extremely well and reminds us of one of our favorite ebike conversions based on a washing machine motor instead of a drill press.

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A man is shown standing in a wooded area, in front of a stone wall, facing toward the camera. To the left of him, on a rock, are a selection of compasses. Further to the left, another scene is shown, of two compasses. One has a brass-colored metal ring around it, and a timer above it reads 00:04:19. A timer above the other reads 01:47:02.

A New Kind Of Inductively-damped Compass

January 11, 2026 by Aaron Beckendorf 42 Comments

At some point during our primary school careers, most of us probably constructed a simple compass, often by floating a magnetized needle on a cork in a cup of water. The water in such a configuration not only lets the needle spin without friction, but also dampens out (so to speak) the needle’s tendency to swing back and forth across the north-south line. Liquid-filled compasses use the same principle, but even well-made compasses can develop bubbles when exposed to temperature or pressure variations. Rather than accept this unsightly state of affairs, [The Map Reading Company] designed a new kind of liquid-free, inductively-damped compass.

It’s hard to design a compass that settles quickly, even if it uses a strong magnet, because the Earth’s own magnetic field is just so weak, and the stronger the internal magnet is, the more likely it is to be thrown off by nearby magnetic objects. As a result, they tend to swing, overshoot, and oscillate around their final orientation for some time. Most compasses use liquid to damp this, but a few, mostly military compasses, use a conductive baseplate instead: as the magnet moves, it induces eddy currents in the baseplate, which create a weak magnetic field opposing its motion, slowing the magnet down. Inductively-damped compasses don’t get bubbles, but they don’t let you see a map through the baseplate. [The Map Reading Company] dealt with this by making the baseplate transparent and surrounding the compass needle with a ring of high-conductivity copper alloy. This gave him a clear baseplate compass for easy map reading which would never develop bubbles. It’s a simple hack, and should be easy to replicate, but it still seems to be a new design. In fact, [The Map Reading Company] is releasing most of the design to the public domain. Anyone can build this design.

If this prompts your interest in compasses, check out the Earth inductor compass. We’ve also seen a visualization of the eddy currents that damp these oscillations, and even seen them used to drive a bike.

Thanks to [Mel] for the tip!

Using The Wind And Magnets To Make Heat

June 25, 2024 by Dan Maloney 53 Comments

On the face of it, harnessing wind power to heat your house seems easy. In fact some of you might be doing it already, assuming you’ve got a wind farm somewhere on your local grid and you have an electric heat pump or — shudder — resistive heaters. But what if you want to skip the middleman and draw heat directly from the wind? In that case, wind-powered induction heating might be just what you need.

Granted, [Tim] from the Way Out West Blog is a long way from heating his home with a windmill. Last we checked, he didn’t even have a windmill built yet; this project is still very much in the experimental phase. But it pays to think ahead, and with goals of simplicity and affordability in mind, [Tim] built a prototype mechanical induction heater. His design is conceptually similar to an induction cooktop, where alternating magnetic fields create eddy currents that heat metal cookware. But rather than using alternating currents through large inductors, [Tim] put 40 neodymium magnets with alternating polarity around the circumference of a large MDF disk. When driven by a drill press via some of the sketchiest pullies we’ve seen, the magnets create a rapidly flipping magnetic field. To test this setup, [Tim] used a scrap of copper pipe with a bit of water inside. Holding it over the magnets as they whiz by rapidly heats the water; when driven at 1,000 rpm, the water boiled in about 90 seconds. Check it out in the video below.

It’s a proof of concept only, of course, but this experiment shows that a spinning disc of magnets can create heat directly. Optimizing this should prove interesting. One thing we’d suggest is switching from a disc to a cylinder with magnets placed in a Halbach array to direct as much of the magnetic field into the interior as possible, with coils of copper tubing placed there.
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Robot 3D Prints Giant Metal Parts With Induction Heat

March 29, 2023 by Bryan Cockfield 36 Comments

While our desktop machines are largely limited to various types of plastic, 3D printing in other materials offers unique benefits. For example, printing with concrete makes it possible to quickly build houses, and we’ve even seen things like sugar laid down layer by layer into edible prints. Metals are often challenging to print with due to its high melting temperatures, though, and while this has often been solved with lasers a new method uses induction heating to deposit the metals instead.

A company in Arizona called Rosotics has developed a large-scale printer based on this this method that they’re calling the Mantis. It uses three robotic arms to lay down metal prints of remarkable size, around eight meters wide and six meters tall. It can churn through about 50 kg of metal per hour, and can be run off of a standard 240 V outlet. The company is focusing on aerospace applications, with rendered rocket components that remind us of what Relativity Space is working on.

Nothing inspires confidence like a low-quality render.

The induction heating method for the feedstock not only means they can avoid using power-hungry and complex lasers to sinter powdered metal, a material expensive in its own right, but they can use more common metal wire feedstock instead. In addition to being cheaper and easier to work with, wire is also safer. Rosotics points out that some materials used in traditional laser sintering, such as powdered titanium, are actually explosive.

Of course, the elephant in the room is that Relativity recently launched a 33 meter (110 foot) tall 3D printed rocket over the Kármán line — while Rosotics hasn’t even provided a picture of what a component printed with their technology looks like. Rather than being open about their position in the market, the quotes from CEO Christian LaRosa make it seem like he’s blissfully unaware his fledgling company is already on the back foot.

If you’ve got some rocket propellant tanks you’d like printed, the company says they’ll start taking orders in October. Though you’ll need to come up with a $95,000 deposit before they’ll start the work. If you’re looking for something a little more affordable, it’s possible to convert a MIG welder into a rudimentary metal 3D printer instead.

New Possibilities From Fading Lighting Technology

February 25, 2023 by Bryan Cockfield 54 Comments

Like the incandescent bulb before it, the compact fluorescent (CFL) bulb is rapidly fading into obscurity as there are fewer and fewer reasons to use them over their LED successors. But there are plenty of things to do with some of the more interesting circuitry that made these relatively efficient light bulbs work, and [mircemk] is here to show us some of them.

Fluorescent bulbs require a high voltage to work properly, and while this was easy enough for large ceiling installations, it was a while until this hardware could be placed inside a bulb-sized package. When removed, the high voltage driver from the CFL is used in this case to drive a small inductive heating coil circuit, which can then be used to rapidly heat metals and other objects. After some testing, [mircemk] found that the electronics on the CFL circuit board were able to easily handle the electrical load of its new task.

When old technology fades away, there are often a lot of interesting use cases just waiting to be found. [mircemk] reports that he was able to find these light bulbs at an extremely low price due to low demand caused by LEDs, so anyone needing a high voltage driver board for something like a small Tesla coil might want to look at a CFL first.