Expansion Board Puts Spotify On The Amiga 500

No doubt some purists in the audience will call this one cheating, since this Amiga 500 from 1987 isn’t technically connecting to Spotify and playing the music by itself. But we also suspect those folks might be missing the point of a site called Hackaday. With all the hoops [Daniel Arvidsson] hopped through to make this happen, what else could it be if not a hack?

This one starts, like so many projects these days, with the Raspberry Pi. Don’t worry Amiga aficionados, this classic machine hasn’t been gutted and had its internals replaced with a diminutive Linux board. But thanks to an expansion card known as the A314, you could say it’s received a penguin infusion. This clever board allows an internally mounted Raspberry Pi to communicate with the Amiga 500 through shared memory, making all sorts of trickery possible.

In this case, the Raspberry Pi is actually the one connecting to the Spotify Connect service with raspotify and decoding the stream. But thanks to a few pipes and an ALSA plugin, the audio itself is actually pushed into the Amiga’s sound hardware. In the video after the break, the process is demonstrated with tunes that are befitting a computer of this vintage.

This process is similar to how one classic Apple fan got Spotify running on their Macintosh SE/30 with a similar respect for the vintage hardware. Of course if you actually want to gut your Amiga 500 and replace it with a Raspberry Pi, we’ve seen some pretty good conversions to get you started.

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Thermochromic Display Tells You The Temperature Despite Your Current Mood

Readers who survived the 1970s will no doubt remember the “mood ring” fad, where a liquid crystal mounted to a ring would magically reveal your current emotional state to all and sundry by changing color. This nifty thermochromic display is based on the same principle, and while it might not start a new craze, it’s still pretty mesmerizing to watch.

This isn’t [Moritz v. Sivers]’ first attempt at a thermochromic display. His earlier version was far more complicated, using separate copper plates clad with thermochromic film for each segment, with Peltier devices to cool and heat them individually. Version two is much simpler, using a printed circuit board with heating elements in the shape of seven-segment displays etched into it. The thermochromic film sits directly on the heater PCB; a control PCB below has the MCU and sensors on it. The display alternates between temperature and humidity, with the segments fading in an uneven and ghostly way that really makes this fun to watch. [Moritz] has made the build files available, and there’s a detailed Instructable as well.

We’re always on the lookout for alternate display modalities, especially when they look this cool. We’ve seen other thermochromic displays before, of course, and persistence of phosphorescence looks great, too.

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This V8 Makes A Shocking Amount Of Power

As a work of art, solenoid engines are an impressive display of electromagnetics in action. There is limited practical use for them though, so usually they are relegated to that realm and remain display pieces. This one from [Emiel] certainly looks like a work of art, too. It has eight solenoids, mimicking the look and internal workings of a traditional V8.

There’s a lot that has to go on to coordinate this many cylinders. Like an internal combustion engine, it takes precise timing in order to make sure that the “pistons” trigger in the correct order without interfering with each other through the shared driveshaft. For that, [Emiel] built two different circuit boards, one to control the firing of each solenoid and another to give positional feedback for the shaft. That’s all put inside a CNC-machined engine block, complete with custom-built connecting rods and shafts.

If you think this looks familiar, it’s because [Emiel] has become somewhat of an expert in the solenoid engine realm. He started off with a how-to for a single piston engine, then stepped it up with a V4 design after that. That leaves us wondering how many pistons the next design will have. Perhaps a solenoid version of the Volkswagen W12?

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3D Printed Dogbox Transmission Kicks Your Desk Into High Gear

It’s often been our experience that some of the most impressive projects are the passion builds, the ones where the builder really put in their all and obsessed over every detail. Even if they don’t always have a practical application, it’s impossible to look at the final product and not respect the accomplishment.

Case in point, this absolutely incredible 3D printed model of a sequential “dogbox” transmission created by [Indeterminate Design]. All of the STL files and a complete bill of materials are available for anyone brave enough to take on the challenge. It might never be mounted to a vehicle and driven around the track, but you can still flick through the gears and watch the complex gearing do its thing.

Even if you don’t want to necessarily build the model itself, [Indeterminate Design] takes you through the concepts behind this unique transmission and how it differs from the sort of gearboxes us lowly commuter drivers are familiar with. He’s even nice enough to explain what a dogbox is.

Put simply, this type of transmission allows the driver to simply move the gear change forward and backwards to step through the gears like in a video game. This prevents you from having to navigate an H-pattern gear shift while dealing with all the other stresses of competition driving. Watching it in action, you can certainly see the appeal.

If you prefer your printed gearboxes to be of the practical variety, we’ve certainly seen plenty of those as well. They’re perfect for next time you need to move an anvil around the shop.

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Keep The Family At Bay While Working From Home With This WiFi Do Not Disturb Dongle

Those who have been suddenly introduced to the wonderful world of working from home over the last couple of weeks may have experienced a bit of culture shock. Even with today’s open floorplan workspaces and less-formal expectations, work isn’t home. That’s especially true with young children in the house, who’ll probably respond to seeing mommy or daddy working from home much differently than [Bob] from accounting would at the office.

To smooth out the rough spots of transitioning to a full-time work-from-home setup, [Brian Lough] threw together this web-enabled “do not disturb” beacon for his office door. The original idea was to simply provide a red light and a green light to let the rest of the family know when [Brian] would be in a meeting, but in an example of scope creep that turned out to be useful, [Mrs. Lough] rewrote the spec to include a button on the family-facing side so that she could alert him that his presence is requested.

[Brian] went through a couple of prototype using both an ESP32 and an ESP8266. We were rooting for the ESP32, which [Brian] was leveraging for its built-in capacitive touch input. That would have eliminated a physical button, but alas, the ESP8266 made it into the final build, along with lots and lots of Blu-Tack. The video below details the build and the code, and features an adorable Irish lesson as a bonus.

Yes, a simple text message would probably have satisfied the specs, but where’s the sport in that? Then again, as [Brian] points out, this build seemed oddly familiar for a good reason.

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Linux Fu: Mapping Files

If you use C or C++, you have probably learned how to open a file and read data from it. Usually, we read a character or a line at a time. At least, it seems that way. The reality is there are usually quite a number of buffers between you and the hard drive, so your request for a character might trigger a read for 2,048 characters and then your subsequent calls return from the buffer. There may even be layers of buffers feeding buffers.

A modern computer can do so much better than reading using things using old calls like fgetc. Given that your program has a huge virtual address space and that your computer has a perfectly good memory management unit within it, you can ask the operating system to simply map the file into your memory space. Then you can treat it like any other array of characters and let the OS do the rest.

The operating system doesn’t necessarily read the entire file in at one time, it just reserves space for you. Any time you hit a page that isn’t in memory, the operating system grabs it for you invisibly. Pages that you don’t use very often may be discarded and reloaded later. Behind the scenes, the OS does a lot so you can work on very large files with no real effort. The call that does it all is mmap.

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Hackaday Podcast 059: Hydraulic Rockets And Presses, Machine Vision That Bounces And Stares, And Smart Speakers That Listen To You

Hackaday editors Mike Szczys and Elliot Williams undertake a journey through the week of fantastic hacks. Add a new level of complexity to model rockets by launching them from a silo via pneumatic ram before the combustibles even get involved. The eyes of that sculpture are actually following you — and with laser focus! The Game Boy is a pillar of pop culture for a reason, there’s a superb talk that outlines all of the interesting choices that made the electronics so special. We round out the show with a rousing discussion of a space tow truck and a scholarly look at the sporadic wake patter of Alexa et al.

Take a look at the links below if you want to follow along, and as always tell us what you think about this episode in the comments!

Direct download (~60 MB)

Places to follow Hackaday podcasts:

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