The STM32 Makes For A Cheap DIY USB Soundcard

May 24, 2022 by Lewin Day 14 Comments

Soundcards used to be giant long 8-bit ISA things that would take up a huge amount of real estate inside a desktop computer. These days, for most of us, they’re baked into the motherboard and we barely give them a second thought. [Samsonov Dima] decided to whip up a cheap little sound card of their own, however, built around the STM32.

The soundcard is based specifically on the STM32F401. readily available on the “Green Pill” devboards. A digital-to-analog converter is implemented on the board based on two PWM timers providing high-quality output. There’s also a simulated software sigma delta ADC implemented between the audio streaming in via USB and the actual PWM output, with some fancy tricks used to improve the sound output. [Samsonov] even found time to add a display with twin VU meters that shows the audio pumping through the left and right channels.

Without test gear on hand, we can’t readily quantify the performance of the sound card. However, as per the Youtube videos posted, it appears more than capable of recreating music with good fidelity and plenty of fine detail.

If you need a cheap, simple USB sound card that you can hack away on, this might be the one for you. If you need something more suitable for a vintage PC, however, consider this instead. Video after the break.

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PCB Linear Motors For Model Trains

May 19, 2022 by Anne Ogborn 34 Comments

Modeling a railroad is hard. Railroads are large, linear pieces of civil engineering. So many modelers are drawn to the smallest scale they can use. Recently a new scale, named T, at 1:450 has been pushing this barrier. But fitting a reliable mechanical drive mechanism and MCU board in a package this size is a challenge. In practice, even more of a problem is getting reliable electrical contact through a metal wheel on metal track (about the worst possible design for a contact).

T always seemed to us a long way out on the bleeding edge. But all that may have changed. In a recent Hackaday.io writeup, author [Martin] describes a PCB technology based linear motor system to externally drive T scale locomotives.

The system uses 4mm planar coils. The underside of the PCB has another coil, so the effective pitch is 2mm. With microstepping, a step of 0.25mm is possible, and trains run smoothly. Current is 3-400mA. Continue reading “PCB Linear Motors For Model Trains” →

Color(ing) Computer Needs No Batteries

May 18, 2022 by Al Williams 3 Comments

While Radio Shack did have the Color Computer, we don’t think they had this in mind. [Pepepépepe] has some coloring book pages and simple rules that let you simulate logic circuits using a crayon. The downloadable ‘zine has hand-written instructions and several examples.

Keep in mind, this is a computer in the same way the old logic kits in the 1960s were computers. They are really demonstrations of digital logic circuits. To work the “computers”, you pick two colors, one for a square and the other for a circle. You color pathways until you reach a “nory.” The nory, which looks suspiciously like a slingshot with eyes, has a special rule. If both branches of the nory have your circle color on them, the output of the nory will be the square color. Otherwise, the color coming out is the circle color.

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Falling Down The Labyrinth With Wooden Microphone Design

May 17, 2022 by Dan Maloney 7 Comments

It used to be that when we featured one of [Frank Olson]’s DIY ribbon microphone builds, it was natural to focus on the fact that he was building them almost exclusively from wood. But despite how counterintuitive it may seem, and for as many comments as we get that his microphones shouldn’t work without metal in the ribbon motors, microphones like this wooden RCA Model 77 reproduction both look and sound great.

But ironically, this homage features a critical piece that’s actually not made of wood. The 77’s pickup pattern was cardioid, making for a directional mic that picked up sound best from the front, thanks to an acoustic labyrinth that increased the path length for incoming sound waves. [Frank]’s labyrinth was made from epoxy resin poured into a mold made from heavy paper, creating a cylinder with multiple parallel tunnels. The tops and bottoms of adjacent tunnels were connected together, creating an acoustic path over a meter long. The ribbon motor, as close to a duplicate of the original as possible using wood, sits atop the labyrinth block’s output underneath a wood veneer shell that does its best to imitate the classic pill-shaped windscreen of the original. The video below, which of course was narrated using the mic, shows its construction in detail.

If you want to check out [Frank]’s other wooden microphones, and you should, check out the beautiful Model 44 replica that looks ready for [Sinatra], or the Bk-5-like mics he whipped up for drum kit recording.

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Vicious Little Desktop Shredder Pulverizes Plastic Waste

May 15, 2022 by Dan Maloney 21 Comments

We’ve all likely seen video of the enormous industrial shredders that eat engine blocks for lunch and spit out a stream of fine metal chips. The raw power of these metal-munching monsters is truly fearsome, and they appear to be the inspiration for SHREDII, the miniature plastic shredder for at-home recycling of plastic waste.

The fact that SHREDII isn’t all that large doesn’t make it any less dangerous, at least to things smaller and softer than engine blocks, like say fingers. The core of the shredder is a hexagonal axle carrying multiple laser-cut, sheet steel blades. The rotating blades are spaced out along the axle so they nest between a bed of stationary blades; rotating the common axle produces the shearing and cutting action needed to shred plastic.

On version one of the shredder, each blade had two hooked teeth, and the whole cutting head was made from relatively thick steel. When driven by a NEMA 34 stepper — an admittedly odd choice but it’s what they could get quickly — through a 50:1 planetary gearbox, the shredder certainly did the business. The shreds were a little too chunky, though, so version two used thinner steel for the blades and gave the rotary blades more teeth. The difference was substantial — much finer shreds that were suitable for INJEKTO, their homebrew direct-feed injection molding machine.

There’s a lot to be said for closing the loop on plastics used in desktop manufacturing processes, and the team of SHREDII and INJEKTO stands to help the home gamer effectively reuse plastic waste. And while that’s all to the good, let’s face it — the oddly satisfying experience of watching a shredder like this chew through plastic like it isn’t even there is plenty of reason to build something like this.

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Upcycling A Flat Bed Scanner

May 15, 2022 by Al Williams 34 Comments

[Piffpaffpoltrie] had a 20-year-old Acer flatbed scanner that they just couldn’t justify keeping. But it does seem a shame to throw away a working piece of gear. Instead, the old scanner became a light table. We’ll admit, as projects go, it isn’t the most technically sophisticated thing we’ve ever seen, but we do think it is a worthy way to upcycle something that would otherwise be filling up a landfill.

The scanner was old enough to have a CCFL light source inside. However, it was too small, so it came out along with many other components that may yet find use in another project. If you didn’t know , scanners are good sources for small stepper motors, straight rods, and first-surface mirrors.

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Barely HDMI Display Gets A Steampunk-Inspired Enclosure

May 13, 2022 by Dan Maloney 21 Comments

It’s an interesting question: What does one do for a follow-up to building the world’s worst HDMI display? Simple — stick it in a cool steampunk-inspired case and call it a day.

That seems to have been [mitxela]’s solution, and please don’t take our assessment as a knock on either the original build or this follow-up. [mitxela] himself expresses a bit of wonder at the attention garnered by his “rather stupid project,” which used the I2C interface in an HDMI interface to drive a tiny monochrome OLED screen. Low refresh rate, poor resolution — it has everything you don’t want in a display, but was still a cool hack that deserved the attention it got.

The present work, which creates an enclosure for the dodgy display, is far heavier on metalworking than anything else, as the video below reveals. The display itself goes in a small box that’s machined from brass, while the HDMI plug gets a sturdy-looking brass housing that makes the more common molded plastic plug look unforgivably flimsy — hot glue notwithstanding. Connecting the two is a flexible stalk, allowing it to plug into a computer’s HDMI port and giving the user the flexibility to position the nearly useless display where it can be seen best.

But again, we may be too harsh in our judgment; while DOOM is basically unplayable on the tiny display, “Bad Apple!!” is quite watchable, especially when accompanied by [mitxela]’s servo-controlled MIDI music box. And since when has usability been a criterion for judging a hack’s coolness, anyway?

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