Retrotechtacular: Build Your Own Dune Buggy, 1970s Style

March 26, 2024 by Jenny List 21 Comments

The custom car phenomenon is as old as the second-hand car, yet somehow the decades which stick in the mind as their heyday are the 1960s and 1970s. If you didn’t have a dune buggy or a van with outrageously flared arches and an eye-hurting paint job you were nothing in those days — or at least that’s what those of us who were too young to possess such vehicles except as posters on our bedroom walls were led to believe. Periscope Films have put up a period guide from the early 1970s on how to build your own dune buggy, and can we just say it’s got us yearning to drive something just as outrageous?

Of course, auto salvage yards aren’t bursting with Beetles as donor cars in 2024, indeed the accident-damaged model used in the film would almost certainly now be lovingly restored instead of being torn apart to make a dune buggy. We’re taken through the process of stripping and shortening the Beetle floorpan, for which we’re thankful that in 2024 we have decent quality cutting disks, and watching the welder joining thin sheet metal with a stick welder gives us some serious respect for his skills.

Perhaps the part of this video most likely to raise a smile is how it portrays building a car as easy. Anyone who has ever hacked a car to pieces will tell you that’s the easy part, and it’s the building something from the pile of rusty parts which causes so many projects to fail. But given an accident damaged Beetle and a buggy kit in 1972 would we have dug in and given it a try? Of course!

We’ve touched on the Beetle’s hackability in the past, but some of us believe that the crown of most hackable car rests elsewhere.

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A Dial Phone SIPs Asterisk

March 24, 2024 by Jenny List 11 Comments

An endless source of amusement for those of advancing years can come from handing a rotary phone to a teenager and asking them to dial a number with it. It’s rare for them to be stumped by a piece of technology, after all. [Mnutt]’s 4-year-old son had no such problems when he saw rotary phones at an art exhibition, so what was a parent to do but wire the phone to an Asterisk PBX with shortcut numbers for calls to family and such essential services as a joke line, MTA status, or even a K-pop song.

It’s possible to hook up a pulse dial phone with a SLIC module and a microcontroller, but in this case, a Grandstream SIP box did the trick. These are all-in-one devices that implement a SIP client with a physical connection, and older ones will talk to pulse dialers as well as the more usual tone dialing phones. The phone in question is a vintage American model. Writing this from Europe we were surprised to find a little simpler inside than its transatlantic counterparts of the same era.

An Asterisk install on a Raspberry Pi completed the project, and thus it became a matter of software configuration. It’s a useful run-through for Asterisk dilettantes, even if you haven’t got a 4-year-old. Perhaps you have an old payphone or two!

An ASIC For A Secret File

March 24, 2024 by Jenny List 6 Comments

Some time over a decade ago, the arrival of inexpensive PCB fabrication revolutionised the creation of custom electronics on a budget. It’s now normal for even the smallest projects we feature here to have a professional PCB, which for those of us who started by etching their own with ferric chloride is nothing short of a miracle. When it comes to the ultimate step in custom electronics of doing the same for integrated circuits though, it’s fair to say that this particular art is in its infancy. The TinyTapeout project is a collaborative effort in which multiple designers have the chance to make their own ASIC as a single tile on a chip along others, and [Bitluni] had the chance to participate. His ASIC? A secret file which could be read through his ESP32 to VGA board.

The video below the break then is both the tale of the secret file project, and that of TinyTapeout itself, which is a clever design involving an on-board microcontroller that selects the tile and manages the bus. This revision is Tiny Tapeout 3, which includes 249 tiles of contributor-generated circuitry holding a diverse array of projects.

The secret file itself is a motion GIF, compressed down until the point at which it will just fit on a tile. We’ll preserve the fun by not reveling what it us, but you probably won’t be surprised when you see it in the video.

We’ve featured TinyTapeout more then once, not least when [Matt Venn] gave a talk about it for Supercon 2022.

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New Pens For Old Plotters

March 23, 2024 by Jenny List 17 Comments

Finding consumables is an ever-present problem facing anyone working with old computer hardware. Many of these devices ceased manufacture decades ago and what old stock remains is invariably degraded by time. [Retrohax] has encountered it with the pens for an Atari plotter, a machine that uses an ALPS mechanism that appears in more than one 1980s machine. The original pens had dried out beyond the ability to refill, so he takes us through the process of finding replacements.

Sadly there are no equivalent modern pens ripe for modification, so whatever replacement he used would have to involve a little lateral thinking. He thought salvation was at hand in the form of multicolor ballpoint refills of the type where the ink is in an easily cuttable plastic tube. [Retrohax] and was able to make a 3D-printed holder for a cut-down ballpoint refill. Sadly the pressure required for a good line from a ballpoint was much higher than the original pens, so he was back to square one. Then he happened upon gel pens and tried the same trick with a gel pen refill. This gave instant success and should provide a valid technique for more than just this ALPS mechanism.

If you haven’t got a classic plotter to hand, never fear. You can have a go at making your own.

The Electromagnetic Field 2024 Badge Is A Little Different

March 23, 2024 by Jenny List 4 Comments

It’s a problem that faces every designer of an event badge: how to make something that won’t simply become a piece of e-waste once the last attendee has gone home. Various events have had badges with extra sensors, ones designed to be dev boards, and ones that try to do useful software tasks, but this year’s Electromagnetic Field in the UK has a different take. Its badge is designed to be used across multiple events, with the badge itself being a hub for event-specific add-ons.

To achieve this feat, the Tildagon badge is a hexagonal hub with an expansion port on every side. Each of these sports an edge connector, and the corresponding part of the add-on is simply part of the PCB. The ‘hexpansions’ as the add-ons are called, don’t even have to have electronics, at their simplest they can even be cut from a piece of card. The brain of the outfit is an ESP32-C3 sporting a round LCD. Of course, and it has the usual buttons and LEDs.

We applaud the sentiment behind making a badge live beyond the event, and we expect that this won’t be the only take on a reusable badge we’ll see over the coming events. We’re guessing those edge connectors will add to the BoM cost though, which is why this probably will be the first EMF badge for which there will be a modest charge. We look forward to seeing it for real, meanwhile, they also published some technical info alongside the announcement linked above.

A Tape Echo For Anyone

March 20, 2024 by Jenny List 7 Comments

If you’ve ever looked into how artists from the 1960s made their music, you’ll learn about the many inventive ways in which the tape recorder enabled new effects. One of the simplest of those is the tape echo, as distinct from a reverb which introduces the many delayed echoes of a large auditorium, an echo provides a single delayed version of the original. It’s something [Mark Gutierez] shows us as he makes a tape echo from a cheap Walkman-style cassette player. It’s hardly the highest quality of its ilk, but it does the job.

The player in question sports the ubiquitous Chinese mechanism that’s the last still in production. It has a radio incorporated which he doesn’t use, but for all that it has only a permanent magnet erase head rather than one driven from the bias oscillator. He first puts another head in the space between the record head and the pinch roller, then further modifies the cassette so a loop can be pulled out of the side of it, moving all heads off-board. As you can see in the video below the break it’s in no way high-fidelity, but with a couple of Eurorack mixer kits added on it makes for an interesting effect.

If you can lay your hands on a reel-to-reel machine, you can make a more traditional echo machine.

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The F Number On A Lens Means Something? Who Knew!

March 18, 2024 by Jenny List 59 Comments

The Raspberry Pi has provided experimenters with many channels of enquiry, and for me perhaps the furthest into uncharted waters it has led me has come through its camera interface. At a superficial level I can plug in one of the ready-made modules with a built-in tiny lens, but as I experiment with the naked sensors of the HD module and a deconstructed Chinese miniature sensor it’s taken me further into camera design than I’d expected.

I’m using them with extra lenses to make full-frame captures of vintage film cameras, in the first instance 8 mm movie cameras but as I experiment more, even 35 mm still cameras. As I’m now channeling the light-gathering ability of a relatively huge area of 1970s glass into a tiny sensor designed for a miniature lens, I’m discovering that maybe too much light is not a good thing. At this point instead of winging it I found it was maybe a good idea to learn a bit about lenses, and that’s how I started to understand what those F-numbers mean.

More Than The Ring You Twiddle To Get The Exposure Right

lose-up of the end of a lens, showing the F-number range — The F-number range of a 1990s Sigma consumer-grade zoom lens.

I’m not a photographer, instead I’m an engineer who likes tinkering with cameras and who takes photographs as part of her work but using the camera as a tool. Thus the f-stop ring has always been for me simply the thing you twiddle when you want to bring the exposure into range, and which has an effect on depth of field.

The numbers were always just numbers, until suddenly I had to understand them for my projects to work. So the first number I had to learn about was the F-number of the lens itself. It’s usually printed on the front next to the focal length and expressed as a ratio of the diameter of the light entrance to the lens focal length. Looking around my bench I see numbers ranging from 1:1 for a Canon 8mm camera to 1:2.8 for a 1950s Braun Paxette 35 mm camera, but it seems that around 1:1.2 is where most 8 mm cameras sit and 1:2 is around where I’m seeing 35 mm kit lenses. The F-stop ring controls an adjustable aperture, and the numbers correspond to that ratio. So that 1:2 kit lens is only 1:2 at the F2 setting, and becomes 1:16 at the F16 setting.

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