Low-Cost Electret Microphone Preamplifiers

October 16, 2023 by 8 Comments

Before the invention of microelectromechanical system (MEMS) microphones, almost all microphones in cell phones and other electronics were a type of condenser microphone called the electret microphone. The fact that this type of microphone is cheap and easy enough to place into consumer electronics doesn’t mean they’re all low quality, though. Electret microphones can have a number of qualities that make them desirable for use recording speech or music, so if you have a struggling artist friend like [fvfilippetti] has who needs an inexpensive way to bring one to life, take a look at this electret microphone pre-amp.

The main goal of the project is to enhance the performance of these microphones specifically in high sound pressure level (SPL) scenarios. In these situations issues of saturation and distortion often occur. The preampl design incorporates feedback loops and an AD797 opamp to reduce distortion, increase gain, and maintain low noise levels. It also includes an output voltage limiter using diodes to protect against input overload and can adjust gain. The circuit’s topology is designed to minimize distortion, particularly in these high SPL situations.

Real-world testing of the preamp confirms its ability to handle high SPL and deliver low distortion, making it a cost-effective solution for improving the performance of electret microphones like these. If you want to go even deeper into the weeds of designing and building electret microphones and their supporting circuitry, take a look at this build which discusses some other design considerations for these types of devices.

[Ken] Looks At The 386

October 16, 2023 by 27 Comments

The 80386 was — arguably — Intel’s first modern CPU. The 8086 was commercially successful, but the paged memory model was stifling. The 80286 also had a protected mode, which differed from the 386’s. [Ken Shirriff] takes the 386 apart for us in a recent blog post.

The 286’s protected mode was less successful than the 386 because of several key limitations as it was a 16-bit processor with a 24-bit address bus. It still required segment changes to access larger amounts of memory, and it had no good way to call back into real mode for compatibility reasons. The 386 fixed all that. You could adopt a segment strategy if you wanted to. But you could also load the segment registers once to point to a 4 GB linear address space and then essentially forget them. You also had a virtual 86 mode that could simulate real mode with some work.

The CPU used a 1-micron process, compared to the 1.5-micron process used earlier. The chip had 285,000 transistors (although the 80386SL had many more). That was ten times the number of devices on the 8086. The cheaper 386SX did use the 1.5 micron process for a while, but with a 16-bit external bus, this was feasible. While 285,000 sounds like a lot, a Core i9 has around 4.2 billion transistors. Times have changed.

A smaller design also allowed chips like the 386SL for laptops. The CPU took up only about a fourth of the die. The rest held bus controllers and cache interfaces to cut costs on laptops. That’s why it had so many more transistors.

[Ken] does his usual in-depth analysis of both the die and the history behind this historic device. We spent a lot of time writing protected mode 386 code, and it was nice to see the details of a very old friend. These days, you can get a pretty capable CPU system on a solderless breadboard, but designing a working 386 system took a few extra parts. The 80286 was a stepping stone between the 8086 and 80386, but even it had some secrets to give up.

AI-Powered Snore Detector Shakes The Pillow So You Won’t

October 14, 2023 by 18 Comments

If you snore, you’ll probably find out about it from someone. An elbow to the ribs courtesy of your sleepless bedmate, the kids making fun of you at breakfast, or even the lady downstairs calling the cops might give you the clear sign that you rattle the rafters, and that it’s time to do something about it. But what if your snores are a bit more subtle, or you don’t have someone to urge you to roll over? In that case, this AI-powered haptic snore detector might be worth building.

The most distinctive characteristic of snoring is, of course, its sound, and that’s exactly what [Naveen Kumar] chose as a trigger. To differentiate between snoring and other nighttime sounds, [Naveen] chose an Arduino Nicla Voice sensor board, which sports a Syntiant NDP120 deep-learning processor and a built-in MEMS microphone. To generate a model that adequately represents the full tapestry of human snores, a publicly available snoring dataset — because of course that’s a thing — was used for training. Importantly, the training data included samples of non-snoring sounds, like sirens and thunder, as well as clips of legit snoring mixed with these other sounds. The model is trained with an online tool and downloaded onto the board; when it detects the sweet sound of sawing wood three times in a row, a haptic driver board vibrates the pillow as a gentle reminder to reposition. Watch it in action in the brief video below.

Snoring is something that’s easy to make light of, but in all seriousness, it’s not something to be taken lightly. Hats off to [Naveen] for developing a tool like this, which just might let you know you’ve got a problem that bears a closer look by a professional. Although it might work better as a wearable rather than a pillow-shaker.

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Hackaday Podcast Ep 240: An Amazing 3D Printer, A Look Inside Raspberry Pi 5, And Cameras, Both Film And Digital

October 13, 2023 by 6 Comments

Date notwithstanding, it’s your lucky day as Elliot and Dan get together to review the best hacks of the week. For some reason, film photography was much on our writers’ minds this week, as we talked about ways to digitalize an old SLR, and how potatoes can be used to develop film (is there a Monty Python joke in there?) We looked at a 3D printer design that really pulls our strings, the custom insides of the Raspberry Pi 5, and the ins and outs of both ferroresonant transformers and ham radio antennas. Learn about the SMD capacitor menagerie, build a hydrogen generator that probably won’t blow up, and listen to the differences between a mess of microphones. And that’s not all; the KIM-1 rides again, this time with disk drive support, Jenny tests out Serenity but with ulterior motives, and Kristina goes postal with a deep dive into ZIP codes.

Check out the links below if you want to follow along, and as always, tell us what you think about this episode in the comments!

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2023 Halloween Hackfest: Musical Jack-o-Lanterns Harmonize For Halloween

October 12, 2023 by 4 Comments

Halloween is many things to many people. For some, it’s a chance to dress up and let loose. For others, it’s a chance to give everyone in the neighborhood a jump scare. For [Aaron], it’s the perfect time to put on a show in the yard with some musical, light-up jack-o-lanterns.

[Aaron] came across some deeply-discounted light-up jack-o-lanterns a few years ago. They all had one of those Try Me buttons that’s powered by a couple of coin cells and uses a temporary two-wire connection to the PCB, and [Aaron] figured he could remotely control them using this port of sorts.

Now the guts are made of addressable RGB LEDs that are connected through the battery compartment via weatherproofed pigtails.

On the control side, he has a Raspberry Pi 3, an amplifier, and a couple of power supplies all housed in a weatherproof box. Since it’s not possible to multiplex both the lights and the audio on a Pi 3, he added a USB sound card into the mix.

Be sure to check out the awesome demo video after the break, followed by a pumpkin conversion video.

If you’re more into scaring people, carve up an animated evil-eye pumpkin.

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Screech Owl Is A Tribute To The Eowave Persephone

October 12, 2023 by 6 Comments

The Eowave Persephone was a beautiful thing—a monophonic ribbon synth capable of producing clean, smoothly varying tones. [Ben Glover] used to own a nice example that formerly belonged to Peter Christopherson, but lost it in the shifting sands of time. His solution was to build one of his own from scratch.

It’s a simple build, but the final result puts out a nice pleasant sound.

Known as the Screech Owl, the build is based around a custom shield designed to suit the Arduino Leonardo. The primary control interface is a Softpot 500 mm membrane potentiometer, layered up with a further thin film pressure sensor which provides aftertouch control. The Leonardo reads these sensors and synthesizes the appropriate frequencies in turn.

All the electronics is wrapped up inside a tidy laser-cut enclosure that roughly approximates the design of the original Eowave device. [Ben] noted the value of services like Fiverr and ChatGPT for helping him with the design, while he also enjoyed getting his first shield design professionally manufactured via JLCPCB.

It’s a tidy build, and in [Ben’s] capable hands, it sounds pretty good, too. We’ve seen some other great ribbon controlled synths before, too. Video after the break.

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A Buzzing, Flashing Phone Ringer For The Elderly

October 11, 2023 by 8 Comments

For a lonely person, elderly or otherwise, the sound of a ringing phone can be music to the ears, unless of course it’s another spam call. But what good is a phone when you can’t hear it well enough to answer?

[Giovanni Aggiustatutto] was tasked with building an additional ringer for a set of cordless landline phones belonging to an elderly friend. Rather than try to intercept the signal, [Giovanni] chose to simply mic up the phone base that’s connected to the phone port on the router and send a signal over Wi-Fi to a second box which has a loud piezo buzzer and a handful of LEDs.

At the heart of this build is a pair of ESP8266 Wemos D1 minis and an Arduino sound sensor module inside a pair of really nice-looking 3D printed boxen that may or may not have been inspired by an IKEA air quality sensor. On the receiving side, a green LED indicates the system is working, and the red LEDs flash as soon as a call comes in.

All the code, schematics, and STL files are available for this build, and between the Instructable and the build video after the break, you should have no trouble replicating it for the hard-of-hearing in your life.

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