3D Printed Air Raid Siren Sounds Just Like The Real Thing

Air raid sirens have an important job to do, and have been a critical piece of public safety infrastructure in times of geopolitical turmoil. They sound quite unlike anything else, by virtue of their mechanical method of generating an extremely loud sound output. They’re actually remarkably simple to build yourself, as [MarkMakies] demonstrates.

[Mark’s] build relies almost entirely on 3D printed components and ex-RC gear. The sound itself is generated by a rotor which spins inside a stator. Each is designed with special slots, such that as the rotor turns at speed, it creates spikes of air pressure that generate a loud wail. The rotor and stator are fitted inside a housing with a horn for output, which helps direct and amplify the sound further.

To spin the rotor, [Mark] used a powerful brushless motor controlled by a common hobby speed controller. The actual speed is determined by a potentiometer, which generates pulses to command the speed controller via a simple 555 circuit. By ramping the speed of the motor up and down, it’s possible to vary the pitch of the siren as is often done with real air raid sirens. This action could be entirely automated if so desired.

If you do decide to build such a siren, just be wary about how you use it. There’s no need to go around agitating the townsfolk absent an actual air raid. It’s worth noting that sirens of this type aren’t just used for air raids, either. They’re often used for tornado warnings, too, such as in Dallas, for example. But why not for music?

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AI System Drops A Dime On Noisy Neighbors

“There goes the neighborhood” isn’t a phrase to be thrown about lightly, but when they build a police station next door to your house, you know things are about to get noisy. Just how bad it’ll be is perhaps a bit subjective, with pleas for relief likely to fall on deaf ears unless you’ve got firm documentation like that provided by this automated noise detection system.

OK, let’s face it — even with objective proof there’s likely nothing that [Christopher Cooper] is going to do about the new crop of sirens going off in his neighborhood. Emergencies require a speedy response, after all, and sirens are perhaps just the price that we pay to live close to each other. That doesn’t mean there’s no reason to monitor the neighborhood noise, though, so [Christopher] got to work. The system uses an Arduino BLE Sense module to detect neighborhood noises and Edge Impulse to classify the sounds. An ESP32 does most of the heavy lifting, including running the UI on a nice little TFT touchscreen.

When a siren-like sound is detected, the sensor records the event and tries to classify the type of siren — fire, police, or ambulance. You can also manually classify sounds the system fails to understand, and export a summary of events to an SD card. If your neighborhood noise problems tend more to barking dogs or early-morning leaf blowers, no problem — you can easily train different models.

While we can’t say that this will help keep the peace in his neighborhood, we really like the way this one came out. We’ve seen the BLE Sense and Edge Impulse team up before, too, for everything from tuning a bike suspension to calming a nervous dog. Continue reading “AI System Drops A Dime On Noisy Neighbors”

Dub Siren, a 555-powered synthesizer

Classic Chip Line-Up Powers This Fun Dub Siren Synth

There’s a certain elite set of chips that fall into the “cold, dead hands” category, and they tend to be parts that have proven their worth over decades, not years. Chief among these is the ubiquitous 555 timer chip, which nearly 50 years after its release still finds its way into the strangest places. Add in other silicon stalwarts like the 741 op-amp and the LM386 audio amp, and you’ve got a Hall of Fame lineup for almost any project.

That’s exactly the complement of chips that powers this fun little dub siren. As [lonesoulsurfer] explains, dub sirens started out as actual sirens from police cars and the like that were used as part of musical performances. The ear-splitting versions were eventually replaced with sampled or synthesized siren effects for recording studio and DJ use, which leads us to the current project. The video below starts with a demo, and it’s hard to believe that the diversity of sounds this box produces comes from just a pair of 555s coupled by a 741 buffer. Five pots on the main PCB control the effects, while a second commercial reverb module — modified to support echo effects too — adds depth and presence. I built-in speaker and a nice-looking wood enclosure complete the build, which honestly sounds better than any 555-based synth has a right to.

Interested in more about the chips behind this build? We’ve talked about the 555 and how it came to be, taken a look inside the 741, and gotten a lesson in LM386 loyalty.

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2018’s Hottest Accessory Is A 3D Printed Air Raid Siren

Some say the spectre of global nuclear annihilation is closer than ever before. What better time to head to the workshop to prepare for the coming apocalypse? [MrExpert] is here with the build you need – an air raid siren you can print at home.

It’s a simple build, which makes it fun and accessible for just about anyone with a 3D printer. Rotational power is provided by a brushless outrunner motor hooked up to an ESC, controlled with a servo tester. The rotor and frame for the parts are 3D printed, and held together with a handful of standard fasteners.

Initial testing proves that yes, it does work and generates a rather earsplitting tone. The second revision improves upon this somewhat. However, the key to getting that authentic sound is in the sweep of the tone. By replacing the servo tester with an Arduino or other micro that can generate smoothly sweeping pulses to ramp the rotational speed up and down, you’ll get much closer to that genuine the-sky-is-falling timbre.

It’s certainly not rocket science, and would make a great project to whip up with the kids on a rainy weekend. While you’re at it you can share the wisdom behind the duck and cover technique, but maybe save the geopolitical rants for when they’re a bit older. We’ve seen air raid siren builds before, too – like this sturdy wooden unit.

Annoy Your Neighbors With MIDI Musical Siren

[Yannick], aka [Gigawipf] brings us this (mostly) musical delicacy: a 3D-printed siren that’s driven by a brushless quadcopter motor, and capable of playing (mostly) any music that you’ve got the MIDI score for. This is a fantastic quickie project for any of you out there with a busted quad, or even some spare parts, and a 3D printer. Despite the apparent level of difficulty, this would actually be a great quickie weekend build.

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Drawn In By The Siren’s Song

When I say “siren” what do you think of? Ambulances? Air raids? Sigh. I was afraid you were going to say that. We’ve got work to do.

You see, the siren played an important role in physics and mathematics about 150 years ago. Through the first half of the 1900s, this fine apparatus was trivialized, used for its pure noise-making abilities. During the World Wars, the siren became associated with air raids and bomb shelters: a far cry from its romantic origins. In this article, we’re going to take the siren back for the Muses. I want you to see the siren in a new light: as a fundamental scientific experiment, a musical instrument, and in the end, as a great DIY project — this is Hackaday after all.

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April Fools’ Project Teaches Coworkers Not To Touch Your Stuff

april-fools-siren-box

Take one look at the sticker on top of this project box and it’s pretty clear you’re not supposed to flip the switch protected by the piece of red plastic. But if your coworkers are anything like [The Timmy’s] there’s at least a few who will stop by and just can’t keep their hands off. He built this to teach those sorts a lesson. Flip the switch and a very loud siren starts blaring. The thing is, the 107db alarm can’t be turned off by the switch, you must have the key for the switch on the side.

The siren is a self-contained unit that just needs a power source between 6V and 15V. This makes the project quite simple, the only part that [The Timmy] really needed to think about was how to build a mechanical SR Latch (set-reset). The solution is to use a mechanical relay. The toggle switch connects the normally open connector to the common terminal to enable the relay. The key switch breaks the relay’s connection to ground, allowing the magnetic switch to open again.

If you need some help understanding how the relay connections work we’ve embedded an unrelated video after the break.

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