A rotary subwoofer made out of a speaker coil, a medium-size fan an a grey wooden box to stand on.

Tear Apart Your House For $200 With This Rotary Subwoofer

September 8, 2023 by Julian Scheffers 44 Comments

Many movies and songs use a lot of of bass to make it feel more real to the viewer or listener. Because of this, subwoofers are common in high-quality audio setups, often costing a substantial part of the budget. [Daniel Fajkis] takes the subwoofer to it’s logical extreme by building a rotary subwoofer on a $200 budget.

The principle of a rotary subwoofer is that a normal subwoofer physically moves the air, and so does a fan. If you could make a fan oscillate the air instead of only pushing it, you could turn it into such a subwoofer, which is exactly what [Daniel] did. [Daniel] mounts a large electric motor on the case of an ex-subwoofer to spin the fan. Then, he uses the rotor linkage of a model helicopter and a modified subwoofer speaker to pitch the fan blades, spinning around to create a truly impressive gust of air oscillating at as low as 1 Hz.

The video, after the break, is well made with some good humor, including the legendary quote: “It’s gonna tear apart my household, there’s no way we’re surviving this one.”
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Tiny PCB Banishes Soldering Fumes, Automatically

February 19, 2023 by Donald Papp 28 Comments

A fan to remove fumes is a handy thing to have when soldering, even better is a fan furnished with a filter. Better still is a fan that activates only when the iron is in use, turning off when the iron is in its stand. Now that’s handy!

[Petteri Aimonen] made exactly such a device when he noticed his JBC BT-2BWA soldering station could detect when the iron is removed from its stand, and indicate its operating mode via status LEDs. Broadly speaking, when the iron is removed from its cradle the green “in use” LED is on. By turning the fan on whenever that LED is lit (and turning it off when it becomes unlit), fume extraction gets a little more elegant and efficient.

Instead of tapping directly into the soldering station’s hardware to detect the LED’s state, [Petteri] went for a completely noninvasive solution that made good use of a few spare parts and a small bit of copper-clad board. The PCB is nothing more than piece of copper-clad board with lands scratched out with a hobby knife.

This tiny board sits atop the soldering station, parking a photodiode directly above the “in use” LED. The circuit is a simple comparator whose output controls fan power via a MOSFET, and a top-facing LED provides as a duplicate “in use” indicator, since the original is hidden under the tiny board.

Even for one-off designs like this, creating a PCB layout in an EDA program like KiCad is still worth doing because one can use it to scratch out lands on a copper-clad board, a technique with similarities to Manhattan-style circuit construction.

Spy Drone Propeller Makes For A Quiet PC

February 6, 2023 by Al Williams 45 Comments

MIT recently announced its research on toroidal propellers to create quieter drones. That got [Major Hardware] thinking about noisy PC fans. The obvious solution was to adapt the toroidal shape for a PC fan. He was familiar with the idea from similar screws on boats that are commercially available. You can see his tests in the video below.

The shape of the blades on the MIT drones is visible in video and pictures, but there were no available 3D models. [Major] did a design and 3D printed the blades. Watching the comparison with a conventional fan using smoke was pretty impressive.

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Flapping PCB Fan Blows A Little Bit

August 23, 2022 by Danie Conradie 24 Comments

Moving air with spinning blades is the most popular way, but it is not the only way. Using the PCB actuator technology he has been working on for the past few years, [Carl Bugeja] built a small electromagnetic flapping fan using a custom flexible PCB.

Inspired by expensive piezoelectric fans ($400 for a 30mW fan), [Carl] wanted to see if a cheaper alternative could be made. Using a similar design to his other PCB actuators, he had a custom flexible PCB made with an integrated coil, which can flex on two thin supports. These supports also contain the power traces for the coil. By sticking the base of the PCB between two neodymium magnets, it can flap back and forth when driven by an alternating current. It produces a bit of airflow, but nearly enough to be useful. The power traces in the thin supports also break after an extended period of 180° flapping.

Although this probably won’t be a viable replacement for a rotary fan, it would be interesting to see how far one can push this approach by optimizing the design and magnet arrangement.

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3D-Printed Parts Let You Assemble Your Own Biggest Fan

March 17, 2022 by Dan Maloney 14 Comments

It’s getting close to the time of year when we need to start carefully vetting projects here at Hackaday. After all, nobody likes to get punked by an early April Fool’s joke. But as silly as this outsized PC fan looks, it sure seems like a legit build, if a bit on the pointless side.

Then again, perhaps pointless is too harsh a word to use. This 500-mm fan is by [Angus] over at Maker’s Muse, and it represents a lot of design work to make it buildable, as well as workable and (mostly) safe. Using both CNC-cut MDF and printed parts, the fan is an embiggened replica of a normal-sized case fan. The fan’s frame had to be printed in four parts, which lock together with clever interlocking joints. Each of the nine blades locks into a central hub with sturdy-looking dovetails.

And sturdy is important, as the fan is powered by a 1,500 Watt brushless DC motor. With a 4:1 reduction thanks to a printed gear train, the fan spins at around 3,300 RPM, which makes a terrifying noise. There’s a little bit of “speed-wobble” evident, but [Angus] managed to survive testing. The fan, however, did not — the 3D-printed gears self-destructed after a full-speed test, but not before the fan did its best wind tunnel imitation. And the RGB LEDs looked great.

This one reminds up of something we might see [Ivan Miranda] come up with. In fact, his super-sized 3D printer might have been just the thing to shorten [Angus]’ print times.

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Homemade Toy Wind Tunnel Blows (Really Well)

February 18, 2022 by Adam Zeloof 6 Comments

Sometimes a kid wakes up on Christmas morning and runs downstairs, only hoping to see one thing: a shiny new wind tunnel. This past December, that’s exactly what [SparksAndCode]’s son found ~~under~~ beside the tree, complete with a bag of scarves, ping-pong balls, and other fun things to launch through it (in the name of physics, of course).

The real story here starts about a week before Christmas, when [SparksAndCode]’s son was enthralled by a similar device at a science museum. At his wife’s suggestion, [SparksAndCode] got to work designing a and building a wind tunnel with hardware-store parts, his deadline looming ahead. The basic structure of the tunnel is three rods which support plywood collars. The walls are formed by plastic sheets rolled inside the collars to make a tube. Underneath, a Harbor Freight fan supplies a nice, steady stream of air for endless entertainment.

After finding a few bugs during his son’s initial beta testing on Christmas morning, [SparksAndCode] brought the wind tunnel back into the shop for a few tweaks and upgrades, including a mesh cover on the air intake to stop things from getting sucked into the fan. The final result was a very functional (and fun!) column of air. Looking for even more function (but not necessarily less fun)? We’ve got you covered too with this home-built research wind tunnel from a few years back.

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The Air Multiplier Fan Principle, Applied To A Jet Engine

January 28, 2022 by Jenny List 26 Comments

Many readers will be familiar with the Dyson Air Multiplier, an ingenious bladeless fan design in which a compressor pushes jets of air from the inside edge of a large ring. This fast-moving air draws the surrounding air through the ring, giving the effect of a large conventional fan without any visible moving parts and in a small package. It’s left to [Integza] to take this idea and see it as the compressor for a jet engine, and though the prototype you see in the video below is fragile and prone to melting, it shows some promise.

His design copies the layout of a Dyson with the compressor underneath the ring, with a gas injector and igniter immediately above it. The burning gas-air mixture passes through the jets and draws the extra air through the ring, eventually forming a roaring jet engine flame exhaust behind it. Unfortunately the choice of 3D print for the prototype leads to very short run times before melting, but it’s possible to see it working during that brief window. Future work will involve a non-combustible construction, but his early efforts were unsatisfactory.

It’s clear that he hasn’t created the equivalent of a conventional turbojet. Since it appears that its operation happens when the flame has passed into the center of the ring, it has more in common with a ramjet that gains its required air velocity with the help of extra energy from an external compressor. Whether he’s created an interesting toy or a useful idea remains to be answered, but it’s certainly an entertaining video to watch.

Meanwhile, this isn’t the first project we’ve seen inspired by the Air Multiplier.

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