Chasing A Long-Obsolete Tube

June 20, 2020 by Jenny List 12 Comments

Regular readers will know that here at Hackaday we have a penchant for poking fun at the more silly end of the audiophile world, with its dubious accessories and purple prose. It’s worth remembering though that this is not representative of the whole discipline of audio design, indeed the quest for perfect audio reproduction contains plenty of complex engineering problems.

We’re indebted to [macsimski] then for sending us a link to a page from Phaedrus Audio from a year or two ago, in which they discuss the history of an unusual pentode tube used as an impedance converter in a series of legendary post-war microphones. It’s unlikely that you’ll have a Neumann U47 or U48 broadcast microphone on your bench, but even so the story behind their design is one that should fascinate anyone.

It takes us back to the period immediately following the Second World War, when German electricity supplies were varied and unreliable, and radio receivers designed for them required new tubes from the manufacturers. Among these was the VF14, with an unusual high-voltage heater designed such that two of them could be connected in series across the supply. This and its compact shape prompted its selection for the professional microphones, even though its performance was so poor that only a third of the production passed the performance test.

Since it passed out of production in the early 1950s the remaining components are extremely rare, and the majority of those surviving do not meet the performance characteristics of the microphone. The Phaedrus write-up goes into significant technical detail which should be of note to anyone with an interest in tubes, and ends up with their reason for it all, a plug-in hardware simulation of the original tube’s properties. Vintage capacitor microphones may be out of the ordinary for Hackaday, but it’s still a good read.

For a bit more on capacitor microphones it’s worth a look at our dive into electrets.

Header image: JacoTen / CC BY-SA 3.0

Seeing Code: The Widescreen Rant

June 20, 2020 by Elliot Williams 114 Comments

A couple of weeks ago, Linus Torvalds laid down the law, in a particularly Linusesque sort of way. In a software community where tabs vs. spaces can start religious wars, saying that 80-character-wide code was obsolete was, to some, utter heresy. For more background on how we got here, read [Sven Gregori]’s history piece on Hackaday, and you’ll learn that sliced bread and the 80-character IBM punch card both made their debut in July, 1928. But I digress.

When I look at a codebase, I like to see its structure, and I’m not alone. That’s one of the reasons for the Linux Kernel style guide’s ridiculously wide 8-character tabs. Combined with a trend for variable names becoming more and more descriptive, which I take to be a good thing, and monitors’ aspect ratios growing seemingly without end, which I don’t, the 80-column width seems like a relic from the long-gone era of the VT-220.

In Linus’ missive, we learn that he runs terminals at 100 x 50, and frequently drags them out to a screen-filling 142 x 76. (Amateur! I write this to you now on 187 x 48.) When you’re running this wide, it doesn’t make any sense to line-wrap argument lists, even if you’re using Hungarian notation.

And yet, change is painful. I’ve had to re-format code to meet 73-column restrictions for a book, only to discover that my inline comments were too verbose. Removing even an artificial restriction like the 80-column limit will have real effects. I write longer paragraphs, for instance, on a wider screen.

I see a few good things to come out of this, though. If single thoughts can be expressed on single lines, it makes the shape of the code better reflect its function. Getting rid of pointless wrapping takes up less vertical space, which is at a premium on today’s cinematic monitors. And if it makes inline comments better (I know, another holy war!) or facilitates better variable naming, it will have been worth it.

But any way you slice it, we’re no longer typing on the old 80-character Hazeltine. It’s high time for our coding style and practice to catch up.

Smartglove Helps Cyclists Be Seen

June 20, 2020 by Lewin Day 25 Comments

Cyclists share the road with other vehicles, often leading to problems when drivers fail to see or respect the rider’s space. To try and alleviate these issues, [Matlek] built the Smartglove to help cyclists communicate their intentions to other road users.

The project consists of a glove fitted with an Arduino Nano 33 BLE sense, featuring Bluetooth and motion sensing on board. Combined with TinyML machine learning code, the Arduino is able to sense hand gestures from the rider. These gestures are then interpreted, and relevant messages displayed on an LED screen worn on the rider’s back. Flicking the wrist left and right flashes indicators that the user is about to change direction, while a rearward flick flashes a warning that the user is braking.

It’s a tidy way to integrate vehicle-style lighting into a simple interface for cycling. This has benefits, particularly at night, for allowing other road users to see a cyclist and understand their intentions on the road. Of course, if you really want to be noticed, this bike boombox could also be a big help. Video after the break. Continue reading “Smartglove Helps Cyclists Be Seen” →

Plant’m If You Got’m And Keep’m Alive

June 19, 2020 by Kristina Panos 13 Comments

Having a few plants around is a great way to liven up your living and/or working space. They look nice, you get to watch them grow and change, and some types of plants can actively improve the room’s air quality. But let’s face it — even the easy ones require a baseline level of care that can easily fall by the wayside. After all, the poor things can’t scream out for water or get up and find a sunnier spot for themselves.

[Ine Hocedez] was tired of watching her plants die and not knowing why. The two main culprits involve water and light, though there can be other issues like soil pH and bugs. It’s easy to get the balance wrong, so why not automate everything?

Plant’m is a complete, portable package that [Ine] designed for a school project. A soil moisture sensor dictates the watering schedule via Raspberry Pi, and water is automatically pumped from an elevated tank.

The lamp is meant to supplement the sunlight, not replace it. But that’s the real beauty of this botanical box — [Ine] can just pick it up and try a different spot if the plant droops or shows burnt spots.

Got the sunlight part down for your plant, but can’t remember to water it? Re-purpose an old Keurig and give it an automatic drip.

Learn Quantum Computing With Spaced Repetition

June 19, 2020 by Al Williams 2 Comments

Everyone learns differently, but cognitive research shows that you tend to remember things better if you use spaced repetition. That is, you learn something, then after a period, you are tested. If you still remember, you get tested again later with a longer interval between tests. If you get it wrong, you get tested earlier. That’s the idea behind [Andy Matuschak ‘s]and [Michael Nielsen’s] quantum computing tutorial. You answer questions embedded in the text. You answer to yourself, so there’s no scoring. However, once you click to reveal the answer, you report if you got the answer correct or not, and the system schedules you for retest based on your report.

Does it work? We don’t know, but we have heard that spaced repetition is good for learning languages, among other things. We suspect that like most learning methods, it works better for some people than others.

Continue reading “Learn Quantum Computing With Spaced Repetition” →

Scanning Analog Film For The Last Time

June 19, 2020 by Lewin Day 44 Comments

Film cameras are capable of great resolution, and for a long time were superior in this regard to their digital successors. However, it’s now possible to store digital copies of analog images in superior detail, so [Jan] built a rig to scan their photos for the last time.

The general idea is to take a high enough resolution scan of film negatives or slides, such that there is no need to rescan the images when technology moves forward. To achieve this, [Jan] decided to employ a DSLR to photograph the materials in question. To do this quickly and accurately, with minimal fuss, special lens hoods were 3D printed to hold slides in perfect register in front of the lens. With a flash to provide even light, the results are excellent. Film negatives proved harder, requiring a carefully designed transport mechanism to avoid damaging the fragile materials. With some perseverance, the final tool worked well.

It’s a tidy way of digitally archiving analog photos, and with the resolution of modern cameras, one needn’t worry about lost resolution. We’ve seen mechanised builds for handling other formats too, such as this 8mm scanner. Video after the break.

Continue reading “Scanning Analog Film For The Last Time” →

Vintage Keyboard Gets The QMK Treatment

June 19, 2020 by Tom Nardi 15 Comments

While nobody could deny that computing technology has some a long way in the last few decades, there are many out there who believe peak keyboard was sometime before the turn of the new millennium. They prefer the look, feel, and especially the sounds, of those classic keyboards to what passes for an input device these days. So much so that it’s not uncommon to see one of these old mammoths get freshened up and pushed into service with a modern computer.

Which is exactly what [Juan Pablo Kutianski] has done with his Compaq MX-11800. This keyboard, which is actually a branded version of the Cherry G80-11800, really stands out in a crowd. With an integrated trackball and a two-row arrangement for the function keys, it’s not hard to see why he’d want to show it off. But while the hardware itself was solid, the features and capabilities of this old school keyboard left something to be desired.

The solution was to replace the keyboard’s original electronics with a Teensy++2.0 running the popular QMK firmware. This not only made the keyboard USB, but allowed [Juan] to tweak things such as the trackball sensitivity and add in support for layers and macros. All of which can be managed through VIA, a graphical configuration tool for QMK.

As we’ve seen in so many projects, the combination of QMK running on the Teensy is a powerful tool for getting the most out of your keyboard. Whether breathing new life into a vintage piece of hardware or creating something truly custom like our very own [Kristina Panos] recently did, it’s definitely something to keep in mind if you’re considering any keyboard hacking.