A High Precision ADC That You Can Understand!

April 21, 2023 by Jenny List 8 Comments

In a world where an analogue to digital converter is all too often an integrated peripheral buried inside a microcontroller, it’s easy to forget how simple these devices can be when built from first principles. An entry in our Op-Amp Challenge from [NNNI] demonstrates this perfectly, it’s a high resolution multi-slope ADC for instrumentation purposes, constructed using a mixture of op-amps, logic chips, and a Raspberry Pi Pico. Best of all, it’s easy to understand, so there’s little of that analogue mystique to worry about.

This type of ADC measures an analogue value by counting how long it takes to charge a capacitor to that voltage. A simple version that measures charge time has a few drawbacks, so this project goes from single slope to multi slope by measuring both charge and discharge times compared to the voltage. Pay attention to component matching and reference stability, and such a design can offer a very high resolution measurement.

The value in this project lies not only in the design itself, but also in the extremely comprehensive description of its operation, which should teach most readers a thing or two. That curvy-line PCB is rather nice, too. We used single slope ADCs to read analogue joysticks back in the day, but we certainly learned something here. Want to see another? This isn’t the first dual slope ADC we’ve seen.

Raspberry Pi Camera Conversion Leads To Philosophical Question

April 18, 2023 by Jenny List 31 Comments

The Raspberry Pi HQ camera module may not quite reach the giddy heights of a DSLR, but it has given experimenters access to a camera system which can equal the output of some surprisingly high-quality manufactured cameras. As an example we have a video from [Malcolm-Jay] showing his Raspberry Pi conversion of a Yashica film camera.

Coming from the viewpoint of a photographer rather than a hardware person, the video is particularly valuable for his discussion of the many lens options beyond a Chinese CCTV lens which can be used with the platform. It uses only the body from the Yashica, but makes a really cool camera that we’d love to own ourselves. If you’re interested in the Pi HQ camera give it a watch below the break, and try to follow some of his lens suggestions.

The broken camera he converted is slightly interesting, and raises an important philosophical question for retro technology geeks. It’s a Yashica Electro 35, a mid-1960s rangefinder camera for 35 mm film whose claim to fame at the time was its electronically controlled shutter timing depending on its built-in light meter. The philosophical question is this: desecration of a characterful classic camera which might have been repaired, or awesome resto-mod? In that sense it’s not just about this project, but a question with application across many other retro tech fields.

A working Electro 35 is a fun toy for an enthusiast wanting to dabble in rangefinder photography, but it’s hardly a valuable artifact and when broken is little more than scrap. One day we’d love to see a Pi conversion with a built-in focal length converter allowing the use of the original rangefinder mechanism, but we’ll take this one any day!

How about you? Would you have converted this Yashica, repaired it somehow, or just hung onto it because you might get round to fixing it one day? Tell us in the comments!

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The Eyes Have It With This Solid State Magic Eye

April 12, 2023 by Dan Maloney 8 Comments

The classic “Magic Eye” tuning indicator was a fantastic piece of vacuum tube technology that graced all kinds of electronic gear for a fair fraction of the 20th century. But despite its prevalence, finding a new-old-stock Magic Eye tube is a tall order these days, especially for the rare versions like the 6T5. No worries, though, since direct plug-in solid-state replacements for the 6T5 are now a thing, thanks to [Gord Rabjohn]. Continue reading “The Eyes Have It With This Solid State Magic Eye” →

IBM Selectric Typewriters Finally Get DIY Typeballs

April 11, 2023 by Bryan Cockfield 29 Comments

IBM’s Selectric line of typewriters were quite popular in the 1960s, thanks in part to an innovation called the typeball which allowed for easy font changes on a single machine. Unfortunately, as if often the case when specialized components are involved, it’s an idea that hasn’t aged particularly well. The Selectric typewriters are now around 60 years old and since IBM isn’t making replacement parts, those restoring these machines have had to get somewhat creative like using a 3D printer to build new typeballs.

It sounds like it would be a simple, but much like the frustration caused with modern printers, interfacing automated computer systems with real-world objects like paper and ink is not often as straightforward as we would like. The main problem is getting sharp edges on the printed characters which is easy enough with metal but takes some more finesse with a printed plastic surface. For the print, each character is modelled in OpenSCAD and then an automated process generates the 3D support structure that connects the character to the typeball.

This process was easier for certain characters but got more complicated for characters with interior sections or which had a lot of sharp angles and corners. Testing the new part shows promise, although the plastic components will likely not last as long as their metal counterparts. Still, it’s better than nothing.

Regular Hackaday readers may recall that the ability to 3D print replacement Selectric typeballs has been on the community’s mind for years. When we last covered the concept in 2020 we reasoned that producing them on resin printers might be a viable option, and in the end, that does indeed seem to have been the missing element. In fact, this design is based on that same one we covered previously — it’s just taken this long for desktop resin 3D printing technology to mature enough.

Mechanical GIF Animates With The Power Of Magnets

April 8, 2023 by Dan Maloney 16 Comments

It doesn’t matter how you pronounce it, because whichever way you choose to say “GIF” is guaranteed to cheese off about half the people listening. Such is the state of our polarized world, we suppose, but there’s one thing we all can agree on — that a mechanical GIF is a pretty cool thing.

What’s even better about this thing is that [Mitch], aka [Hack Modular], put some very interesting old aircraft hardware to use to make it. He came upon a set of cockpit indicators from a Cold War-era RAF airplane — sorry, “aeroplane” — that used a magnetically driven rack and pinion to swivel a set of prism-shaped pieces to one of three positions. Which of the three symbols displayed depended on which faces were turned toward the pilot; they were highly visible displays that were also satisfyingly clicky.

After a teardown in which [Mitch] briefly discusses the mechanism behind these displays, he set about customizing the graphics. Rather than the boring RAF defaults, he chose three frames from the famous Horse in Motion proto-motion picture by [Eadweard Muybridge]. After attaching vertical strips from each frame to the three sides of each prism, [Mitch] came up with a driver for the display; he could have used a 555, but more fittingly chose series-connected relays to do the job. Capacitors slow down the switching cascade and the frame rate; a rotary switch selects different caps to make the horse appear to be walking, trotting, cantering, or galloping — yes, we know they’re each physically distinct motions, but work with us here.

The whole thing looks — and sounds — great mounted in a nice plastic enclosure. The video below shows it in action, and we find it pretty amazing the amount of information that can be conveyed with just three frames. And we’re surprised we’ve never seen these displays before; they seem like something [Fran Blanche] or [Curious Marc] would love.

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Tube Amplifier Uses Low Voltage, Sips Battery

April 6, 2023 by Bryan Cockfield 25 Comments

Much like vinyl records, tube amplifiers are still prized for their perceived sound qualities, even though both technologies have been largely replaced otherwise. The major drawback to designing around vacuum tubes, if you can find them at all, is often driving them with the large voltages they often require to heat them to the proper temperatures. There are a small handful of old tubes that need an impressively low voltage to work, though, and [J.G.] has put a few of them to work in this battery-powered audio tube amplifier.

The key to the build is the Russian-made 2SH27L battery tubes which are originally designed in Germany for high-frequency applications but can be made to work for audio amplification in a pinch. The power amplifier section also makes use of 2P29L tubes, which have similar characteristics as far as power draw is concerned. Normally, vacuum tubes rely on a resistive heater to eject electrons from a conductive surface, which can involve large amounts of power, but both of these types of tubes are designed to achieve this effect with only 2.2 volts provided to the heaters.

[J.G.] is powering this amplifier with a battery outputting 5V via a USB connection, and driving a fairly standard set of speakers borrowed from a computer. While there aren’t any audio files for us to hear, it certainly looks impressive. And, as it is getting harder and harder to find vacuum tubes nowadays, if you’re determined to build your own amplifier anyway take a look at this one which uses vacuum tubes built from scratch.

Typewriter Mashup Becomes 120-Year-Old Teletype

April 5, 2023 by Jenny List 13 Comments

Vintage typewriters can be beautiful and elegant devices. But there’s a limit to their value if, as with the 1903 Remington owned by [Daniel Ross], they are fire-damaged and have a seized mechanism. What did he do with what was essentially a piece of scrap metal? Produce an unholy mashup of the vintage machine and a 1988 Sharp daisy wheel typewriter to make a steampunk-style teletype, of course!

Stripping down both machines was evidently no easy task, and the result he’s achieved has the Sharp’s printer mechanism at 90 degrees to its original orientation sitting below the roller in the space once occupied by the Remington’s type bars. We’re sad to see that the keyboard on the older machine appears to be inoperable, but on the other hand each letter does light up as it’s typed.

Meanwhile at the electronics side the components from the Sharp have been transferred to a custom PCB, and the whole can be driven from a 300-baud serial line. As can be seen from the video below the break, the result is an unholy love-child of two typewriters that could scarcely be more different, but somehow it works to make an impressive whole.

If this project looks a little familiar to Hackaday readers, it’s because we’ve mentioned it in passing before. It’s hooked up to his COSMAC Elf retrocomputer, and we saw it in passing a couple of years ago at a much earlier stage of construction before the custom PCB and light-up keyboard.

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