Art With Steppers And STM32

Automotive dashboards are something that largely go untouched in the average car’s life. Other than the occasional wipe with a damp cloth, they’re generally reliable for the life of the car and considered too tricky to repair as age sets in. Nevertheless, some hackers find themselves tinkering with them, and learn skills in the process, such as how to control stepper motors and talk to the CAN bus. Having done some projects in the past, [Dan] had some old tachometers lying around and decided to turn them into a piece of art.

The build is powered by an STM32 – a powerful ARM-based platform with plenty of IO and potential. [Dan] leveraged its capabilities to have the board generate music and react to its onboard accelerometer data while also driving the stepper motors from the old tachometers. The project was then completed by 3D printing a mounting plate and placing the tachometer assemblies into the back of an IKEA canvas print.

The end result is a piece of wall art that emits eerie stringed music while twitching around. It came about from [Dan]’s prior projects in working with dashboards. It’s a fun use of some well-earned hacking skills, but we reckon there’s even more potential. There’s a huge number of projects that could benefit from lightweight tiny actuators, and we’d love to see a robot made entirely out of junkyard dashboard parts.

For another dashboard hack, why not check out this beautiful Jeep desk clock?

The Modern Retrocomputer: An Arduino Driven 6845 CRT Controller

[MmmmFloorPie] revived an old project to create the retro mashup of a 6845 CRT controller and a modern Arduino Uno. When it comes to chips, the Motorola 6845 is the great granddaddy of Cathode Ray Tube (CRT) interfaces. It was used in the IBM Monochrome display adapter, the Hercules graphics controller, CGA, Apple II terminal cards, and a host of other microcomputer and terminal systems.

Way back in 1989, [MmmmFloorPie] was a senior in college. His capstone project was a 68000 based computer which could record and playback audio, as well as display waveforms on a CRT. The CRT in question was ordered from a classified add in Popular Science magazine. It was a bare tube, so the heavy cardboard box it shipped in was repurposed as a case.

Fast forward to today, and  [MmmmFloorPie] wanted to power up his old project. The 68000 board was dead, and he wasn’t up to debugging the hundreds of point to point soldered connections. The CRT interface was a separate board including the 6845 and 32 KByte of RAM. It would only take a bit of hacking to bring that up. But what would replace the microprocessor?

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A Mini-ITX Atari 800

As a community has grown up around the 8-bit microcomputers of the 1980s, there have been some beautifully crafted rebuilds of classic machines to take advantage of newer hardware or to interface to peripherals such as keyboards or displays that were unavailable at the time. Often these have taken the form of small boards, or boards that are designed to follow the form factor of the original machine, and fit in an original case.

[mytekcontrols] has taken a different tack with his Atari 800 build, he’s produced an Atari clone designed to take the most popular upgrade boards produced by the 8-bit Atari community, as daughter boards. And he’s followed an existing form factor, though it’s not one from the Atari world. Instead, he’s made it as a mini-ITX motherboard of the type you may well be familiar with from the world of PCs.

He’s calling it the 1088XEL, because with a popular 1MB upgrade board fitted it boasts a generous 1088k of memory. It sports the original five Atari LSI chips, and manages the task without resorting to surface-mount construction.

The forum thread linked above is a long one that makes for a fascinating read as it deals in depth with the design of an 8-bit micro clone. But if you want to skip straight to the hardware, start at about page 13.

We’ve had more than one 8-bit Atari on these pages over the years. Most memorable though is probably this laptop.

Thanks [Lenore Underwood].

Vintage Plotter Handles Chaos With Ease

No lab in almost any discipline was complete in the 70s and 80s without an X-Y plotter. The height of data acquisition chic, these simple devices were connected to almost anything that produced an analog output worth saving. Digital data acquisition pushed these devices to the curb, but they’re easily found, cheap, and it’s worth a look under the hood to see what made these things tick.

The HP-7044A that [Kerry Wong] scored off eBay is in remarkably good shape four decades after leaving the factory. While the accessory pack that came with it shows its age with dried up pens and disintegrating foam, the plotter betrays itself only by the yellowish cast to its original beige case. Inside, the plotter looks pristine. Completely analog with the only chips being some op-amps in TO-5 cans, everything is in great shape, even the high-voltage power supply used to electrostatically hold the paper to the plotter’s bed. Anyone hoping for at least a re-capping will be disappointed; H-P built things to last back in the day.

[Kerry] puts the plotter through its paces by programming an Arduino to generate a Lorenz attractor, a set of differential equations with chaotic solutions that’s perfect for an X-Y plotter. The video below shows the mesmerizing butterfly taking shape. Given the plotter’s similarity to an oscilloscope, we wonder if some SDR-based Lissajous patterns might be a fun test as well, or how it would handle musical mushrooms.

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The Nintendo PlayStation: Finally Working

The Nintendo PlayStation is not a misnomer. Before the PS1, Sony teamed up with Nintendo to produce a video game console that used CD-ROMs as a distribution platform. These plans fell through, Sony went on to design the PS1, Nintendo the N64, but a few prototype ‘Nintendo PlayStations’ made it out into the wild. One of these unbelievably rare consoles was shipped to a company that eventually went into bankruptcy. The console was found when the contents of an office building were put up for auction, and last year, [Ben Heck] tore it apart.

It’s taken a year, but now this Nintendo PlayStation is finally working. This console now plays audio CDs and games written by homebrewers. The hardware lives, and a console once forgotten lives once more.

The last time [Ben Heck] took a look at the Nintendo PlayStation, the CD-ROM portion of the console was non-functional. The Super Nintendo was still functional, but for this prototype, the CD-ROM was completely self-contained and required a ‘boot cartridge’ of sorts to access anything on a CD. Somehow or another — [Ben] thinks it was a wonky cable or a dead cap — The CD-ROM came to life. Yes, jiggling a cable was the extent of the repair, after spending an inordinate amount of time reverse engineering the console.

With the CD-ROM working, [Ben] got audio playing and tried out of the few homebrew games for this PlayStation prototype. Super Boss Gaiden didn’t quite work because this game was designed to load in chunks. Another game written for this console, Magic Floor, was small enough to fit in the entirety of the CD-ROM’s buffer and loaded correctly. That doesn’t mean the game worked; there are some slight differences between the Nintendo PlayStation emulator and the actual hardware that now exists. [Ben] emailed the author of Magic Floor, and now, after a quarter-century, the Nintendo PlayStation works.

What’s next for the Nintendo PlayStation? Well, now the emulator for this system can correctly reflect the actual hardware, and hopefully the homebrewers can figure out how to write a game for this system.

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Reverse Engineering Space Invaders Sound Chip

Around here, a new blog post from [Ken Shirriff] is almost as exciting as a new Star Trek movie. This time, [Ken] tears apart a 76477 sound effects chip. This chip was state-of-the-art in 1978 and used in Space Invaders, along with plenty of other pinball machines and games.

[Ken] started out with a die photo from [Sean Riddle] and mapped its functions. Unlike a modern sound chip, this one created sounds based on networks of attached resistors and capacitors. Even if you aren’t interested in the chip, per se, [Ken] explains how the die implements active and passive devices, along with some key analog design principles like current mirrors (although we are pretty sure he got his right and his left mixed up, or maybe it was a very subtle mirror joke).

Before electronics magazines were full of computer projects, they were full of music synthesis projects and the 76477 is like a crude synthesizer on a chip. It has voltage controlled oscillators (VCOs),  and generates envelopes with specific attack and decay times to create the sounds of interest.

This reminded us a little of the sounds from the more advanced MOS6581. [Ken] has looked inside a lot of ICs, including at the 2016 Hackaday SuperConference.

Model of a Transmission Line

Transmission lines are the kind of thing that seems to confuse beginners. After all, the fact that short-circuits can have infinite impedance and open-circuits can behave like a short is not intuitive at all!. That’s why we like [Tinselkoala]’s latest video that shows a nice model of a transmission line. It helps to understand the line as inductors and capacitors in series-parallel connection.

Any pair of wires used to transmit electrical power have tiny amounts of inductance and capacitance. This is not a problem with DC or low-frequency AC, but when the frequency is sufficiently high, weird things start to happen. The energy tends to escape as radio waves, and current reflects from discontinuities such as connectors and cable joints.  For this reason, transmission lines for high frequency signals use specialized construction to minimize those effects and reduce power losses.

[Tinselkoala] has built a model of a transmission line using coils and capacitors to simulate the inductance and capacitance of the line, with LED’s placed between the coils. He feeds the system with the signal generator with frequencies from 10 kHz to 1 MHz. In his words, they act as simple “visual voltmeters” to show the peaks and nodes of the standing waves of voltage in the line.

It is relatively simple to build your own version if you want to experiment with this fascinating subject. You will only need some magnet wire, capacitors, resistors and LED’s. If the subject sounds interesting to you,  here you can find an excellent introduction to transmission lines.

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