Making A Nichrome Wirewound Power Resistor

March 28, 2026 by Maya Posch 19 Comments

Although not really a cost-effective or a required skill unless you have some very specific needs not met by off-the-shelf power resistor options, making your own own wirewound power resistor is definitely educational, as well as a fascinating look at a common part that few people spare a thought on. Cue [TheElectronBench]’s video tutorial on how to make one of these components from scratch.

The resistance value is determined by the length of nichrome wire, which is an alloy of nickel and chromium (NiCr) with a resistivity of around 1.12 µΩ/m. It’s also extremely durable when heated, as it forms a protective outer layer of chromium oxide. This makes it suitable for very high power levels, but also requires the rest of the power resistor assembly to be able to take a similar punishment.

For the inner tube of this DIY power resistor a tube of alumina ceramic was used, around which the nichrome wire is wound. This resistor targets 15 Ohm at a maximum load of 50 Watt, this means a current of about 1.83 A is expected at 27.4 V. The used nichrome wire has a measured resistance of 10.4 Ohm, ergo 1.44 meter has to be cut and wound.

This entire assembly is then embedded in refractory cement (fireproof cement), as this will keep the wire in place, while also able to take the intense temperature cycling during operation. As a bonus this will prevent toasting the surrounding environment too much, never mind lighting things on fire as the nichrome wire heats up.

As explained in the video, this is hardly the only way to create such a power resistor, with multiple types of alternative alloys available, different cores to wind around and various options to embed the assembly. The demonstrated method is however one that should give solid results and be well within the capabilities and budget of a hobbyist.

An important point with nichrome is that you cannot really solder to it, so you’ll need something along the lines of a mechanical (crimping) connection. There are also different winding methods that can affect the inductance of the resistor, since this type of resistor is by its design also a coil. This is however not covered in the video as for most applications it’s not an issue.

Overall, this video tutorial would seem to be a solid introduction to nichrome power resistors, including coverage of many issues you may encounter along the way. Feel free to sound off in the comment section with your own experiences with power resistors, especially if you made them as well.

Power Resistance Isn’t Futile

May 14, 2024 by Al Williams 17 Comments

As [Electronoobs] points out, everything has resistance. So, how hard can it be to make a high-power resistor? In the video below, he examines a commercial power resistor and how to make your own using nichrome wire.

Sure, in theory, you can use a long piece of wire, but normally, you want to minimize the amount of space occupied. This leads to winding the wire around some substrate. If you just wind the wire, though, you get an inductor. This can cause nasty voltage spikes when there is a change in current through the resistor. You can get “noninductive” wire wound resistors that use either two opposing windings or alternate the turn direction on each turn. This causes the magnetic fields to tend to cancel out, reducing the overall inductance.

Nichrome wire has more resistance per millimeter and can dissipate more power. Modern digital meters can measure the resistance of a wire if you account for the test leads. To make a substrate, [Electronoobs] got creative since he anticipated generating a lot of heat. The final product even uses water cooling.

Why do you want a big resistor? Maybe you need a dummy load, or you want to drain some batteries. If you want to recycle nichrome wire, it is much more common than you might expect.

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Handy Tool Drains 18650 Cells So You Don’t Have To

February 1, 2021 by Tom Nardi 29 Comments

Draining a battery is easy. Just put a load across the terminals, maybe an incandescent bulb or a beefy power resistor, and wait. What’s quite a bit trickier is doing so safely. Put too large a load on, or leave it connected for longer than necessary, and you can end up doing damage to the cell. Not convinced he’d always remember to pull the battery out of his jury-rigged discharger at the opportune moment, [Jasper Sikken] decided to come up with a simple tool that could automatically handle the process with the cold and calculating precision of silicon.

V4 used the protection module from a pouch battery.

At a glance we can see the major components you’d expect in a discharger: a fairly simple PCB, four ceramic power resistors, a holder for a single 18650 cell, and a rocker switch to connect it all together. But wait, what’s that a TP4056 charging module doing in there?

While its presence technically makes this device a battery charger, [Jasper] is actually using it for the onboard protection IC. With the charging module between the cell and the power resistors, it will cut the connection when the voltage drops to 2.4 V. Oh yeah, and it can charge the battery back up if you connect up a USB cable.

[Jasper] says his little tool works great, with the resistor array putting just enough load on the battery to pull it down quickly without getting so hot that they’re dangerous to have exposed. He estimates the BOM for this gadget runs around $2 USD, and is considering offering it as a kit on Tindie in the near future.

If you’re looking for something a bit more advanced, [Jasper] built a programmable load a few years back that can discharge batteries and test power supplies all while logging the data to your computer for later analysis.

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Building A Heat Sealer For Anti-static Bags

November 17, 2011 by Mike Szczys 22 Comments

[Raphaël Assénat] needed anti-static bags for some boards he is selling. He had a lot of leftovers on hand (presumably from the components he ordered to assemble these boards) and wanted to reuse them. Instead of buying a heat sealer he built his own to cut them down to size.

His build starts with a transformer to drop mains voltage down to 9 Volts. From there, you can see the two power resistors used in series to limit the current. Without these, the wire would get way too hot. Just in front of those resistors is a momentary push switch which cuts the power by default. Here we can see that [Raphaël] is using a wood block to press the bag against the wire as it heats up.

The wire itself is a piece of straightened tension spring. Apparently this spring material is a poor conductor, which is why it gets hot enough to melt the plastic bag when you run current through it.