Simplest Speaker Oscillator, Now Even Simpler

It never fails. Lay down some kind of superlative — fastest, cheapest, smallest — around this place and someone out there says, “Hold my beer” and gets to work. In this case, it’s another, even simpler audio oscillator, this time with just a loudspeaker and a battery.

Attentive readers will recall the previous title holder was indeed pretty simple, consisting only of the mic and speaker from an old landline telephone handset wired in series with a battery. Seeing this reminded [Hydrogen Time] of a lucky childhood accident while experimenting with a loudspeaker, which he recreates in the video below. The BOM for this one is even smaller than the previous one — just a small speaker and a battery, plus a small scrap of solid hookup wire. The wire is the key; rather than connecting directly to the speaker terminal, it connects to the speaker frame on one end while the other is carefully adjusted to just barely touch the flexible wire penetrating the speaker cone on its way to the voice coil.

When power is applied with the correct polarity, current flows through the wire into the voice coil, which moves the cone and breaks the circuit. The speaker’s diaphragm resets the cone, completing the circuit and repeating the whole process. The loudspeaker makes a little click with each cycle, leading to a very rough-sounding oscillator. [Hydrogen Time] doesn’t put a scope on it, but we suspect the waveform would be a ragged square wave whose frequency depends on the voltage, the spring constant of the diaphragm, and the spacing between the fixed wire and the voice coil lead.

Yes, we realize this is stretching the definition of an audio oscillator somewhat, but you’ve got to admit it’s simple. Can you get it even simpler?

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apple airtag being opened to remove the sounder

Apple AirTag: Antitheft Or Antistalking?

Occasionally, the extra features added to a product can negate some of the reasons you wanted to buy the thing in the first place. Take, for example, Apple’s AirTag — billed as an affordable way to link your physical stuff to your phone. If some light-fingered ne’er-do-well wanders by and half-inches your gear, you get notified. The thing is, the AirTag also has an anti-stalking measure, which after a while, notifies nearby iPhones, should the tag move but not be near your iPhone!

In a recent video, [David Manning] explains that this feature is great for preventing the device from being used to track people. But it also means that if said thief happens to own an iPhone, they will be notified of the nearby tag, and can find it and disable it. So in the end, it’s a bit less useful as an anti-theft measure!

The solution is to pop the back off the tag and yank out the little sounder module from the rear plastic. You lose the ability to locate the tag audibly, but you gain a little more chance of returning your stolen goods. Apple could easily remove this feature with a firmware update, but it’s a matter of picking your poison: antistalking or antitheft?

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Reggaeton-Be-Gone Disconnects Obnoxious Bluetooth Speakers

If you’re currently living outside of a Spanish-speaking country, it’s possible you’ve only heard of the music genre Reggaeton in passing, if at all. In places with large Spanish populations, though, it would be more surprising if you hadn’t heard it. It’s so popular especially in the Carribean and Latin America that it’s gotten on the nerves of some, most notably [Roni] whose neighbor might not do anything else but listen to this style of music, which can be heard through the walls. To solve the problem [Roni] is now introducing the Reggaeton-Be-Gone. (Google Translate from Spanish)

Inspired by the TV-B-Gone devices which purported to be able to turn off annoying TVs in bars, restaurants, and other places, this device can listen to music being played in the surrounding area and identify whether or not it is hearing Reggaeton. It does this using machine learning, taking samples of the audio it hears and making decisions based on a trained model. When the software, running on a Raspberry Pi, makes a positive identification of one of these songs, it looks for Bluetooth devices in the area and attempts to communicate with them in a number of ways, hopefully rapidly enough to disrupt their intended connections.

In testing with [Roni]’s neighbor, the device seems to show promise although it doesn’t completely disconnect the speaker from its host, instead only interfering with it enough for the neighbor to change locations. Clearly it merits further testing, and possibly other models trained for people who use Bluetooth speakers when skiing, hiking, or working out. Eventually the code will be posted to this GitHub page, but until then it’s not the only way to interfere with your neighbor’s annoying stereo.

Thanks to [BaldPower] and [Alfredo] for the tips!

A 360° View Of A Classic Drive-In Speaker

Readers of a certain vintage no doubt have pleasant memories of drive-in theaters, and we are chuffed to see that a few hundred of these cinematic institutions endure today. While most theaters broadcast the audio on an FM station these days, the choice is still yours to use the chunky, often crackly speaker that attaches to the car window.

Seeking to relive the drive-in audio experience at home, [codemakesitgo] picked up a drive-in theater speaker on eBay and turned it into a Bluetooth device that sounds much better than it did in its weather-beaten days outside.

There isn’t a whole lot to this build — it’s essentially a new speaker cone, a Bluetooth receiver, an amp, and a battery. The real story is in the way that [codemakesitgo] uses Fusion360 to bring it all together.

After 3D scanning the case, [codemakesitgo] made sure each piece would fit, using a custom-built model of the new speaker and a 3D model of a custom PCB. Good thing, too, because there is barely enough clearance for the speaker. Be sure to check out the brief demo video after the break.

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Upgraded Toy Guitar Plays Music

Getting the finishing details on a Halloween costume completed is the key to impressing friends and strangers alike on the trick-or-treat rounds. Especially when it comes to things like props, these details can push a good Halloween costume to great with the right touches. [Jonathan]’s friend’s daughter will be well ahead of the game thanks to these additions to a toy guitar which is part of her costume this year.

The toy guitar as it was when it arrived had the capability to play a few lackluster sound effects. The goal here was to get it to play a much more impressive set of songs instead, and to make a couple upgrades along the way as well. To that end, [Jonathan] started by dismantling the toy and investigating the PCBs for potential reuse. He decided to keep the buttons in the neck of the guitar despite their non-standard wiring configuration, but toss out the main board in favor of an ESP32. The ESP32 is tasked with reading the buttons, playing a corresponding song loaded on an SD card, and handling the digital to analog conversion when sending it out to be played on the speaker.

The project doesn’t stop there, though. [Jonathan] also did some custom mixing for the songs to account for the lack of stereo sound and a working volume knob, plus he used the ESP32’s wireless capabilities to set the guitar up as a local file server so that songs can be sent to and from the device without any wires. He also released the source code on the project’s GitHub page for anyone looking to use any parts of this project. Don’t forget there’s a Halloween contest going on right now, so be sure to submit the final version of projects like these there!

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2023 Halloween Hackfest: A Spooky “Severance” Speaker

If you know, you know. After becoming fully engrossed in the sci-fi psycho-thriller “Severance“, [Ben Brooks] absolutely needed to have a version of the ominous speaker known as the Board.

This speaker represents the Board, who is the enigmatic governing body of Lumon Industries, the fictional and gigantic biotechnology company featured in the show.

The Board cultivates an air of mystery by rarely speaking, and when it does, it speaks through a single person who paraphrases the Board’s responses. The audio that comes out is a mix of the show’s theme song, pertinent show quotes, and static.

The guts of this freaky little thing are pretty simple — an ESP8266, a DF Player Mini, and a couple of small speakers. In fact, [Ben] had all the parts leftover from a previous home automation project, including the PCB.

Although the original plan was to program it in Arduino, [Ben] ended up using ESPHome to make it easier to integrate with sensors for the big night. Be sure to check out the demo video after the break.

We’ve seen a few fun hacks for the porch this year, including the treat trough of terror and this Ouija robot that out-creeps the real thing.

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A Speaker With Dancing Ferrofluid

A speaker project isn’t usually very different, but we couldn’t help but notice [Electronoob’s] latest speaker not for its audio performance but because it features dancing ferrofluid and is an unusual work of art. The housing is 3D printed and includes some translucent portions for LEDs.You can see and hear the speaker at work in the video below.

Apparently, not all ferrofluid is created equal. You can get just the fluid, but then you have to work up some sort of carrier fluid. You can also get the material already in a glass with a carrier fluid, which is a better option. Apparently, you can also get cheap material that is little more than iron filings suspended in a liquid. That’s not really ferrofluid.

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