classic hacks

2793 Articles

A Foil Tweeter, Sound From Kitchen Consumables

December 31, 2024 by 14 Comments

The world of audio has produced a variety of different loudspeaker designs over the last century, though it’s fair to say that the trusty moving coil reigns supreme. That hasn’t stopped plenty of engineers from trying new ways to make sound though, and [R.U.H] is here with a home-made version of one of them. It’s a foil tweeter, a design in which a corrugated strip of foil is held in a magnetic field, and vibrates when an audio frequency current is passed through it.

He shows a couple of takes on the design, both with neodymium magnets but with different foils and 3D printed or wooden surrounds. They both make a noise when plugged into an amplifier, and unsurprisingly the thicker foil has less of the high notes.

We can see that in there is the possibility for a high quality tweeter, but we can’t help having one concern. This device has an extremely low impedance compared to the amplifier, and thus would probably be drawing far too much current. We’d expect it to be driven through a transformer instead, if he had any care for not killing the amplifier.

Happily there are other uses for a ribbon, they are far better known as microphones.

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A Mechanical Calculator For The Modern Age

December 26, 2024 by 16 Comments

There was a brief period through the 1960s into the 1970s when the last word in electronics was the calculator. New models sold for hundreds of dollars, and owning one made you very special indeed. Then the price of the integrated circuit at their heart fell to the point at which anyone could afford one, and a new generation of microcomputers stole their novelty for ever. But these machines were by no means the first calculators, and [What Will Makes] shows us in detail the workings of a mechanical calculator.

His machine is beautifully made with gears hand-cut from plywood, and follows a decimal design in which the rotation of a gear with ten teeth represents the numbers 0 to 9. We’re taken through the mechanical processes behind addition, subtraction, multiplication, and division, showing us such intricacies as the carry lever or a sliding display mechanism to implement a decimal equivalent of a bitwise shift multiplication.

We have to admit to be particularly impressed by the quality of the work, more so because these gears are hand made. To get such a complex assembly to work smoothly requires close attention to tolerance, easy with a laser cutter but difficult by hand. We heartily recommend watching the video, which we’ve placed below the break.

Meanwhile if you’d like more mechanical calculators, take a look at one of the final generation of commercial models.

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A Twenty-Segment Display, Artistically

December 24, 2024 by 21 Comments

We all know and love the humble seven-segment display, right? And if you want to make characters as well as numbers, you can do an okay job with sixteen segments off the shelf. But if you want something more art-deco, you’ll probably want to roll your own. Or at least, [Ben] did, and you can find his designs up on GitHub.

Taking inspiration from [Posy]’s epic investigation of segmented displays, [Ben] sat down with a sketchpad and created his own 20-segment font that displays numbers and letters with some strange, but frankly lovely, segment shapes. There is no center line, so letters like “T” and numbers like “1” are a little skewed, but we think it’s charming.

We’ve seen about a bazillion takes on the seven-segment idea over the years here. Most recently, we fell in love with this 21-segment beauty, but honestly the original eight(!) segment patent version is charming as well. Anyway, picking a favorite segmented display at Hackaday is like picking your favorite child, if you have a few hundred children. We love them all.

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Tiny arcade machines on a tabletop

Tiny PONG, Big Ambitions: World’s Smallest Arcade

December 11, 2024 by 5 Comments

London, Ontario college student [Victoria Korhonen] has captured the attention of tech enthusiasts and miniaturization lovers with her creation of what might be the world’s smallest arcade machine. Standing just 64 mm tall, 26 mm wide, and 30 mm deep, this machine is a scaled-down marvel playing the classic Atari game PONG. While the record isn’t yet official—it takes about three months for Guinness to certify—it’s clear [Korhonen]’s creation embodies ingenuity and dedication.

[Korhonen], an electromechanical engineering student, took six months to design and build this micro arcade. Inspired by records within reach, she aimed to outdo the previous tiniest arcade machine by shaving off just a few millimeters During the project she faced repeated failures, but viewed each iteration as a step towards success. Her miniature machine isn’t just a gimmick; it’s fully functional, with every component—from paddle mechanics to coding—developed from scratch.

[Korhonen] is already eyeing new projects, including creating the smallest humanoid robot. She also plans to integrate her electromechanical expertise into her family’s escape room business. Her journey aligns with other hobbyist projects pushing the limits of miniaturization, such as this credit card-sized Tetris clone or [Aliaksei Zholner]’s paper micro engines.

KiCad render of µLind pcb

The 6809 8-Bit Microcomputer: A Father-Son Odyssey

December 6, 2024 by 22 Comments

If you’re nostalgic for the golden age of microprocessors and dream of building your own computer, this story might spark your imagination. [Eric Lind], passionate retro enthusiast and his 14-year-old son, embarked on a mission to craft a microcomputer from scratch, centred around the exotic Motorola 6809 chip: the µLind.

What sets this project apart is its ambition: bridging retro computing with modern enhancements. Starting with just a 6809 and some basic peripherals, the men designed a multi-stage roadmap to realize their dream. Each stage brought new challenges: debugging an address decoder, reworking memory management, and evolving glue logic into programmable GAL chips. Fascinatingly, the project isn’t just about nostalgia—it’s a playground for exploring multitasking operating systems and pushing the boundaries of 8-bit computing.

Their creativity shines in solutions like a C64-compatible joystick port, add-on expansion cards, and a memory overkill of 1MB RAM. With every setback—a missing pull-up resistor or a misrouted IRQ signal—their determination grew stronger. By combining old-school know-how with modern tools like KiCad, they’ve created something that is both personal and profoundly inspiring.

[Eric]’s hope and goal is to establish a community of people that want to expand beyond the traditional Z80 and 6502 based SBC’s. Interested? Read [Eric]’s project log on Hackaday.io and start crafting!

A Hundred Year Old Solid State Amplifier

December 5, 2024 by 21 Comments

Conventional wisdom has it that the solid state era in electronics began in 1948 with the invention of the transistor, or if you wish to split hairs, with the 1930s invention by the Russian [Oleg Losev] of an early form of tunnel diode. But there’s an earlier amplifier technology that used a solid state circuit which is largely forgotten, and [AWA Communication Technologies Museum] has featured it in a new video. We’re talking of course about the carbon microphone amplifier, a piece of telephone technology which made its way into consumer electronics.

The carbon microphone is a container of loosely packed carbon granules acted upon by a diaphragm. Vibrations from sound compress and decompress the granules, changing the electrical resistance of the carbon. It was the standard microphone used in telephone handsets for most of the twentieth century. Being a resistor it can be placed in a potential divider circuit that produces some significant voltage swings, so when the vibrations come from a high-impedance earpiece it can make an amplifier. It’s not a very good amplifier, it has lousy bandwidth, distortion, and noise characteristics, but it was just about good enough to be paired with a 1920s crystal set. In the video below the break we see a variety of the devices, and even hear them in action sounding very tinny indeed. At the time it must have seemed miraculous to be at the forefront of the new technology though, and we can’t help admiring some of the construction intricacies.

Carbon microphone amplifiers may be rare today, but for all that we’ve touched on them before.

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PI Board chess board on a table in a room

Chess What: One More Pi-Powered Board

December 3, 2024 by 7 Comments

Chess is timeless, but automating it? That’s where the real magic begins. Enter [Tamerlan Goglichidze]’s Pi Board, an automated chess system that blends modern tech with age-old strategy. Inspired by Harry Potter’s moving chessboard and the commercial Square Off board, [Tamerlan] re-imagines the concept using a Raspberry Pi, stepper motors, and some clever engineering. It’s not just about moving pieces — it’s about doing so with precision and flair.

At its core, the Pi Board employs an XY stepper motor grid coupled with magnets to glide chess pieces across the board. While electromagnets seemed like a promising start, [Tamerlan] found them impractical due to overheating and polarity-switching issues. Enter servo linear actuators: efficient, precise, and perfect for the job.

But the innovation doesn’t stop there. A custom algorithm maps the 8×8 chess grid, allowing motors to track positions dynamically—no tedious resets required. Knight movements and castling? Handled with creative coding that keeps gameplay seamless. [Tamerlan] explains it all in his sleekly designed build log.

Though it hasn’t been long since we featured a Pi-powered LED chess board, we feel that [Tamerlan]’s build stands out for its ingenuity and optimization. For those still curious, we have a treasure trove of over fifty chess-themed articles from the last decade. So snuggle up during these cold winter months and read up on these evergreens!

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