Wurlitzer Note Visualizer Gets A 2020-Spec Replica

June 20, 2020 by Lewin Day 1 Comment

Way back in the 1970s, when smog laws were choking American V8s and the oil crisis was in full swing, Wurlitzer released their Key Note Visualizer. Intended as a teaching aid, the device lit up keys on a keyboard graphic, allowing an organ player to visually demonstrate their performance to a class. [Guy Dupont] set out to replicate this hardware, but with a modern twist.

The build consists of an ESP-32, which accepts MIDI data over Bluetooth Low Energy. This is then used to light up a series of RGB LEDs on a musical staff and a keyboard graphic, corresponding to the notes being played. The LEDs used are the old-school four-wire type, rather than more modern data-driven types. They’re placed in 3D-printed holders which serve to stop the light from each LED bleeding into adjacent areas. The faceplate is made of acrylic, stencilled with that classic orange paint and with vinyl decals applied for the markings. It’s all wrapped up in a walnut case, which [Guy] CNC machined himself.

It’s a tidy build that faithfully recreates the 1970s aesthetic of the original. We plaintively wish that manufacturers would release more electronics in walnut enclosures, though ask politely that they leave cheap veneer in the past where it belongs.

Of course, if you like your musical displays more abstract than instructional, try this giant oscilloscope visualisation on for size. Video after the break.

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Dipole Antenna Is Off Balance

June 20, 2020 by Al Williams 11 Comments

A dipole antenna is easy, right? Two wires, each a quarter wavelength long, emanate from a coax or other feedline. Unless it is an off-center dipole. The length is still the same, but you move the feed point to a different part. [KB9VBR] explains how this changes the antenna’s impedance from the nominal 70 ohms of a standard dipole.

Why would you want to do that? The trick is to find a feed point that has acceptable impedance on multiple ham radio bands. Most automatic tuners can handle a certain range of mismatch so using an antenna like this with a tuner can allow one antenna to serve multiple bands with no traps or switches.

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WiFi Networks Turned Targets In This Pocket Game

June 20, 2020 by Tom Nardi 1 Comment

Looking for a way to make his warwalking sessions a bit more interactive, [Roni Bandini] has come up with an interesting way to gamify the discovery of new WiFi networks. Using a Heltec WiFi Kit 8, which integrates an OLED screen and ESP8266, this pocket-sized device picks up wireless networks and uses their signal strength and encryption type as elements of the game.

After selecting which network they want to play against, a target is placed on the screen. The distance between the target and the player is determined by signal strength, and how much damage the target can take correlates to how strong its encryption is. As you can see in the video after the break, gameplay is a bit reminiscent of Scorched Earth, where the player needs to adjust the angle of their artillery to hit distant targets.

The Heltec board is attached to a 3D printed front panel, which fits neatly into an Altoids tin. The controls consist of a button and a potentiometer, and with the addition of a battery pack salvaged from an old cell phone, this little device is ready to do battle wherever you roam.

While this is just a fun diversion for the time being, [Roni] says it wouldn’t take much to actual log networks to a file and generate some statistics about their strength and encryption type. If the idea of a portable WiFi scanning companion seems interesting, you should definitely check out the Pwnagotchi project.

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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

Great Badge Concept: A “Geiger Counter” For WiFi Deauthentication Frames

June 20, 2020 by Donald Papp 15 Comments

[Nick Price] had a wonderful concept for a DEFCON badge: a device that worked a lot like a directional Geiger counter, but chirped at detecting WiFi deauthentication packets instead of radiation. That’s a wild idea and it somehow slipped past us last year. Why detect such a thing? Well, the WiFi deauth attack is a kind of invisible toxicity, effectively jamming wireless communications by forcing users to be constantly tied up with authentication, and this device would detect it.

A few things were harder than expected, however. To make the device directional, [Nick] designed and built a PCB Yagi antenna but it wasn’t practical. Not only was it far too big, it would also have required going to four layers on a PCB that was already expensive. The solution he settled on — inspired by a friend’s joke about just dropping the badge into a Pringles can — was to surround the PCB omni antenna with a copper pipe end cap from the plumbing section of any hardware store. [Nick] figured that soldering that to the ground plane should result in a simple, cheap, and attractive directional antenna mod. Did it work? We’ll all have to wait and see.

Sadly, [Nick] wasn’t able to finish in time for last year’s DEFCON. Hardware revisions mounted, and fabrication times for his specialized PCB were longer than usual. Worse news is that this year’s is cancelled, or rather is going virtual, which means he’s going to have to deauth himself. The good news is that now he’s got another 12-month extension. Watch the brief video of the functional prototype, embedded below.

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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” →