Set Your Nuts (and Bolts) Free With This Induction Heater

[Amon] built an induction heater to break stuck bolts loose. If you work on cars, machines, or anything big and metal, sooner or later you’re going to run into stuck nuts and bolts. Getting them unstuck usually involves penetrating oil, heat from a torch, and cheater bars. Heat usually works well, as heating the bolt makes the metal expand, helping it to break free. Torches aren’t exactly precision instruments though, and things can get interesting using one in tight spaces.

Fire isn’t the only way to heat a bolt through. Electricity can do the job as well. But why use a heating coil when you can grab an induction heater. Mechanics have had induction heaters in their toolboxes now for a few years, under names such as Bolt Buster or Mini Ductor. These devices cost several hundred dollars. However, you can purchase a 1000 watt induction heater from the usual sources for around $30. These are open frame Zero Voltage Switching (ZVS) power supplies, with uninsulated copper coils.

[Amon] bought one of these induction heaters, along with a beefy 24V, 40 amp switch mode supply to power it. He built the two into a plastic enclosure. A relay energizes the induction heater, so it isn’t always running. The key to this build is the handle. Rather than mount the induction coil directly on the supply, [Amon] ran two extension wires to a 3d printed gun style handle. This keeps the bulky part of the heater away from the work. The copper tube coil was re-shaped to better work with the gun. Some fiberglass sleeve keeps everything insulated, even at extreme temperatures.

The result is a very useful heater, ready to bust loose some bolts. We’ve seen homebuilt ZVS supplies powering induction coils before. It will be interesting to see how well these commercial units hold up.

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Making S’mores With 50,000 Volts

[Skyy] sent us a video of him cooking s’mores with an electric arc. He’s using a flyback transformer with a zero voltage switching (ZVS) driver. This produces about 50 kV, which is more than enough to toast the marshmallow.

ZVS is a technique that triggers the semiconductor switches when they have zero voltage across them. This ensures that there’s minimal heat created by the switches, since they are not interrupting any current at the time they are toggled. ZVS is also used in lighting dimmers to switch off power without creating interference.

If you’re interested in the details, there’s a great tutorial on building the driver. If you’re interested in learning how it works, check out this simulation video.

[Skyy] admits that his setup isn’t terribly safe since it uses a breadboard, which isn’t rated for the high voltages and currents. Keep in mind that these circuits could kill you. After the break, watch a marshmallow fry in a 50 kV arc.

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