Hidden TV-Out On The Nintendo DS Lite

The Game Boy DS Lite was one of Nintendo’s most popular handheld gaming consoles, but unbeknownst to all, it has a hidden feature that could have made it even more popular. Digging through the hardware and firmware of the DS Lite, the [Lost Nintendo History] team discovered the System-on-Chip (SoC) in the Game Boy DS Lite can output a composite video signal.

The SoC can output a 10-bit digital output running at 16.7 MHz, but it is disabled by the stock firmware early in the boot process, so custom firmware was required. It still needs to be converted to an analog signal, so a small adaptor board with a DAC (digital-analog converter) and op-amp is attached to the flex cable of the upper screen. A set of buttons on the board allow you to select which screen is displayed on the TV. The adaptor board is open source, and the Gerbers and schematics are available on GitHub.

The current version of the adaptor board disables the upper screen, but the [Lost Nintendo History] team is considering designing a pass-through board to eliminate this disadvantage. The TV-out mod can also be combined with the popular Macro mod, in which the upper screen is removed to turn it into a Game Boy Advance. The Nintendo DS is a popular hacking subject, and we’ve been covering them for well over a decade.

source https://hackaday.com/2021/02/28/hidden-tv-out-on-the-nintendo-ds-lite/

Fail of the Week: How not to Build a Filament Extruder

It would be great if you could create your own filament. On the face of it, it seems easy to do, but as [Thomas Sanladerer] found out when he was a student, there are a lot of details that can bedevil your design. His extruder sort of works, but he wouldn’t suggest duplicating his effort. In fact, he hopes you can learn what not to do if you try to do it yourself.

In all fairness, [Thomas] was a low-budget student and was trying to economize. For example, he tried using a drill to drive the auger. Why not? It looks like a drill bit. But he found out that wasn’t satisfactory and moved to a pair of wiper motors with their built-in gear train.

The wiper motors allowed him to get some ABS filament, but the machine had more troubles. Other lessons learned were to keep the water cooling tank closed so water doesn’t splash out onto electronics, and that it is hard to look at filament with a CCD sensor.

The controller is a simple Arduino. There are three heat zones before the plastic reaches the die. As you might expect, there’s a PID controller to regulate the machine.

[Thomas] says the flow rate was too high, so slowing down the production might have helped. A smaller auger is also on his list of things he’d do differently in hindsight. The melting area needed a heatbreak much like a 3D printer’s hotend to keep hot plastic from creeping towards the cooler part of the tube and clogging.

With his current experience and a bigger budget, we have no doubt he could end up with a workable extruder. As it is, we always enjoy learning from other people’s suboptimal builds. It is a little humbling to show you failed projects on the Internet, but it is a valuable service, indeed.

We want an extruder that can recycle our junk parts. We’ve seen some really cheap builds, but we don’t really know how well they work.

source https://hackaday.com/2021/02/28/fail-of-the-week-how-not-to-build-a-filament-extruder/

Nissan’s Office Pod Concept is a Productivity Paradise on Wheels

All this working from home is pretty great, but we have to admit that we miss packing up the Hackaday office and heading for the local coffeehouse once in a while to spend a few hours writing against the buzzing background. One thing we don’t miss about the experience is that you’re never guaranteed a place to sit and spread out. And unless you trust a friendly stranger to keep an eye on your stuff while you’re in the bathroom, you have to take it with you at the risk of losing your table.

If only we could afford one of Nissan’s mobile office pod concept vehicles. We’ve always wanted to pretend we’re doing surveillance and would probably have the thing wrapped with graphics for a fake flower shop or something. That would certainly make it easier to park somewhere and borrow someone’s open Wi-Fi network  — maybe even from the coffeehouse parking lot after we hit the drive-thru.

As you’ll see in the extended tour video below, Nissan seem to have thought of everything except restroom facilities. The cab-over-engine design and all-terrain tires would make it easier to drive out into nature and really get away from it all. Once you’ve found the perfect spot, you can open the lift gate for some fresh air, or get some sun while you work by pulling out the motorized unibody-constructed cubicle which includes a built-in Herman Miller Cosm chair. (Evidently the Aeron is old and busted now; we disagree). For some reason, the cubicle is edge-lit, and not in a way that would help you work at the desk. According to the video, it’s based on the Caravan NV350, which looks far more comfortable but not as cool when outfitted as an alternate mobility concept.

The office pod has some nice amenities like a DC-AC converter so you can run your Keurig or Nespresso, and there’s even a UV-disinfecting lamp in the glove box. The larger windows behind the cab can be electronically shaded so you don’t bake in the sun. Here’s where things get a bit ridiculous: the floor is made of clear polycarbonate in case you want to park lengthwise over a small stream and watch the surviving fish go by underneath your feet. And if you really want to take a break, climb up to the roof deck and stretch out in the chaise lounge beneath the deck umbrella.

If we lived anywhere but America, we might forego the flower shop graphics wrap and dress it up to look like a TV detector van instead.

source https://hackaday.com/2021/02/28/nissans-office-pod-concept-is-a-productivity-paradise-on-wheels/

Nissan’s Office Pod Concept is a Productivity Paradise on Wheels

All this working from home is pretty great, but we have to admit that we miss packing up the Hackaday office and heading for the local coffeehouse once in a while to spend a few hours writing against the buzzing background. One thing we don’t miss about the experience is that you’re never guaranteed a place to sit and spread out. And unless you trust a friendly stranger to keep an eye on your stuff while you’re in the bathroom, you have to take it with you at the risk of losing your table.

If only we could afford one of Nissan’s mobile office pod concept vehicles. We’ve always wanted to pretend we’re doing surveillance and would probably have the thing wrapped with graphics for a fake flower shop or something. That would certainly make it easier to park somewhere and borrow someone’s open Wi-Fi network  — maybe even from the coffeehouse parking lot after we hit the drive-thru.

As you’ll see in the extended tour video below, Nissan seem to have thought of everything except restroom facilities. The cab-over-engine design and all-terrain tires would make it easier to drive out into nature and really get away from it all. Once you’ve found the perfect spot, you can open the lift gate for some fresh air, or get some sun while you work by pulling out the motorized unibody-constructed cubicle which includes a built-in Herman Miller Cosm chair. (Evidently the Aeron is old and busted now; we disagree). For some reason, the cubicle is edge-lit, and not in a way that would help you work at the desk. According to the video, it’s based on the Caravan NV350, which looks far more comfortable but not as cool when outfitted as an alternate mobility concept.

The office pod has some nice amenities like a DC-AC converter so you can run your Keurig or Nespresso, and there’s even a UV-disinfecting lamp in the glove box. The larger windows behind the cab can be electronically shaded so you don’t bake in the sun. Here’s where things get a bit ridiculous: the floor is made of clear polycarbonate in case you want to park lengthwise over a small stream and watch the surviving fish go by underneath your feet. And if you really want to take a break, climb up to the roof deck and stretch out in the chaise lounge beneath the deck umbrella.

If we lived anywhere but America, we might forego the flower shop graphics wrap and dress it up to look like a TV detector van instead.

source https://hackaday.com/2021/02/28/nissans-office-pod-concept-is-a-productivity-paradise-on-wheels/

OnShape to Robot Models Made Easier

We live in a time where our phones have computing power that would have been the envy of NASA a few decades ago. So, in theory, we should be able to simulate just about anything. Thanks to [rhoban], robots you design in OnShape — a popular CAD tool — are now easier to simulate using several common simulation tools.

Electronic circuits are pretty easy to simulate, because we typically draw schematics and circuit simulators can capture those schematics readily. But simulating physics for robotic designs is a bit trickier. Gazebo and Pybullet both can use SDF files or URDF. However, building those files is often a separate process from actual physical design even though you probably did the design using a CAD tool. Even if you don’t use OnShape, you can probably import your preferred format and then bridge to the simulation file format without having to manually recreate your design. You can see the author walk through the process in the video below.

The program does use the OnShape API, so you’ll need a key for that. The example quadruped looks like a cool design. Once you have the design in the right format, you can use multiple tools to work with it from a simulation perspective.

We’ve seen URDF exports for SolidWorks before. If you want a chance to play with Pybullet, try Boston Dynamic’s Spot robot.

 

source https://hackaday.com/2021/02/28/onshape-to-robot-models-made-easier/

How to Monitor Blood Pressure Without Raising It

Does anyone actually enjoy the sensation of being squeezed by a blood pressure cuff? Well, as Mom used to say, it takes all kinds. For those who find the feeling nearly faint-inducing, take heart: researchers at UC San Diego have created a non-invasive medical wearable with a suite of sensors that can measure blood pressure and monitor multiple biochemicals at the same time.

The device is a small, flexible patch that adheres to the skin. So how does it manage to measure blood pressure without causing discomfort? The blood pressure sensor consists of eight customized piezoelectric transducers that bounce ultrasonic waves off the near and far walls of the artery. Then the sensor calculates the time of flight of the resulting echoes to gauge arterial dilation and contraction, which amounts to a blood pressure reading.

This patch also has a chemical sensor that uses a drug called pilocarpine to induce the skin to sweat, and then measures the levels of lactate, caffeine, and alcohol found within. To monitor glucose levels, a mild current stimulates the release of interstitial fluid — the stuff surrounding our cells that’s rife with glucose, salt, fatty acids, and a few minerals. This is how continuous glucose monitoring for diabetes patients works today. You can check out the team’s research paper for more details on the patch and its sensors.

In the future, the engineers are hoping to add even more sensors and develop a wireless version that doesn’t require external power. Either way, it looks much more comfortable and convenient than current methods.

source https://hackaday.com/2021/02/27/how-to-monitor-blood-pressure-without-raising-it/

A PCB for a Quarter?

As time has gone by and PCB assembly companies have reached further into the space of affordability for our community, the available types of board have multiplied. No longer are we limited to FR4 with a green solder mask, we can have all colours of the rainbow and a variety of substrates. The folks at BotFactory have taken things a step further with their PCB printer though, by printing a fully-functional PCB on a quarter.

As a base layer the printed five passes of insulation on the coin, before printing the traces. Holes are left in the insulation to create a form of via that connects to the coin. On the board is an ATtiny2313 microcontroller that flashes an LED, and on the reverse side of the coin is a CR2032 cell that’s secured with a set of bolts and washers. You can see it taking shape in the video below the break.

It’s true that an LED flasher isn’t exciting, and that this is a marketing stunt for BotFactory’s printer. But it’s an inventive one, and reminds us that with a bit of ingenuity anything can become a board. We’ve had our share over the years, and instantly springing to mind is this stretchable PCB.

 

source https://hackaday.com/2021/02/27/a-pcb-out-of-a-quarter/

Pool Noodle Robot Shines A Light On The Pros and Cons Of Soft Robots

[James Bruton]’s impressive portfolio of robots has always used conventional rigid components, so he decided to take a bit of a detour and try his hand at a soft robot. Using a couple of few inflatable pool noodles for quick prototyping, his experiments quickly showed some of the strengths and weaknesses of soft robots.

Most of the soft robots we see require an external air source to inflate cells in the robot and make the limbs actuate. Taking inspiration from a recent Stanford research project, [James] decided to take an alternative approach, using partially inflated tubes and squeezing them in one section to make the other sections more rigid. He bought a couple of cheap pool noodles and experimented with different methods of turning them into actuators. The approach he settled on was a pair of noodles tied together side by side, and then folded in half by an elastic cord. As one end is squeezed by a servo bellows, the internal pressure overcomes the tension from the elastic cord, and the “elbow” straightens out.

[James] tested various arrangements of these limbs to build a working hexapod robot but to no avail. The simple actuating mechanism was simply too heavy, and could just lift itself slightly. This highlighted a common theme in almost all the soft pneumatic robots we’ve seen: they carry very little weight and are always tethered to an external air supply. The combination of stretchy materials and relatively low pressure compressed air can only handle small loads, at least in Earth gravity and above water.

However, it wasn’t all failure. [James] had success with a gripper design, which is the one area we have seen practical and commercial success with other soft robots. They do work well for gripping delicate and irregularly shaped objects. If you would like to experiment with [James]’s bellow design, it is open source and available on GitHub.

source https://hackaday.com/2021/02/27/pool-noodle-robot-shines-a-light-on-the-pros-and-cons-of-soft-robots/

Circle Full of LEDs Becomes a Clock

Building a clock of some sorts seems to be a time honored tradition for hackers and LED clocks seem one of the most popular. You can build anything from a seven-segment display to a binary clock or something even more fancy. [Clueless] found a circle of LED rings online and with made an LED version of an analog clock.

The rings aren’t wired together, and it seems like these are designed to be separated, but it’s pretty easy to wire them together in order to have a circle of individually accessible RGB LEDs.  Each hand of the clock is a different color and is antialiased to give a smoother look, since the LEDs don’t line up.  [Clueless] wanted the second hand to rotate smoothly, so it is updated using the milliseconds as an offset to the second.  An ESP8266 runs the code and controls the LEDs getting the time from an NTP server. Occasionally, [Clueless] has the clock display a quick effect, such as a Pac-man or a radar scan animation.

All the files are up on the Github page, including the Blender models for the case, available to build your own and a simple search for “241 LED ring” turns up the LED hardware used. There are plenty of clock projects on the site, like this multicolor LED ring clock and we’re sure that you can find something interesting.

source https://hackaday.com/2021/02/27/circle-full-of-leds-becomes-a-clock/

Exploring The Open Source That Really Goes Into A RISC-V Chip

It’s an exciting time in the world of microprocessors, as the long-held promise of devices with open-source RISC-V cores is coming to fruition. Finally we might be about to see open-source from the silicon to the user interface, or so  goes the optimistic promise. In fact the real story is considerably more complex than that, and it’s a topic [Andreas Speiss] explores in a video that looks at the issue with a wide lens.

He starts with the basics, looking at the various layers of a computer from the user level down to the instruction set architecture. It’s a watchable primer even for those familiar with the topic, and gives a full background to the emergence of RISC-V. He then takes Espressif’s ESP32-C3 as an example, and breaks down its open-source credentials. The ISA of the processor core is RISC-V with some extensions, but he makes the point that the core hardware itself can still be closed source even though it implements an open-source instruction set. His conclusion is that while a truly open-source RISC-V chip is entirely possible (as demonstrated with a cameo Superconference badge appearance), the importance of the RISC-V ISA is in its likely emergence as a heavyweight counterbalance to ARM’s dominance in the sector. Whether or not he is right can only be proved by time, but we can’t disagree that some competition is healthy.

Take a closer look at the ESP32-C3, with our hands-on review.

source https://hackaday.com/2021/02/27/exploring-the-open-source-that-really-goes-into-a-risc-v-chip/

Printing Yoda Heads: Re-Makers Riffing!

We had a comment recently from a nasty little troll (gasp! on the Internet!). The claim was that most makers are really just “copiers” because they’re not doing original work, whatever that would mean, but instead just re-making projects that other people have already done. People who print other peoples’ 3D models, or use other peoples’ hardware or software modules are necessarily not being creative. Debunking a cheap troll isn’t enough because, on deeper reflection, I’m guilty of the same generic sentiment; that feeling that copying other people’s work isn’t as worthy as making your own. And I think that’s wrong!

In the 3D printing world in particular, I’m guilty of dismissively classifying projects as “Yoda Heads”. About ten years ago, [chylld] uploaded a clean, high-res model of Yoda to Thingiverse, and everyone printed it out. Heck, my wife still has hers on her desk; and alone this is proof that straight-up copying has worth, because it made a sweet little gift. After a while, Yoda gave way to Baby Groots, and strangely enough we’re back to Yoda again, but it’s Baby Yoda now.

Does filling the world with more Yoda Heads, vomiting toothpaste or not, further creativity? I’d argue it does. It’s actually a moderately difficult print — those spindly little ears present an overhang challenge that’ll definitely help you calibrate your cooling, or force you to learn something about supports. Pushing your limits in 3D printing teaches you about the tool and what possibilities it presents. Mastering a tool is an important step toward using it creatively. And then there’s “riffing”.

Jazz musicians don’t just get up and play improvisational solos that come magically into their heads. They’ve spent hours in the shed, copying the ways that other players have interpreted the classics. Which is to say, they become creative through copying. Transcendental, inspirational, original moments come about through hours and hours of filtering other peoples’ work through your fingers, ears, and lips until it becomes a part of you and eventually bubbles up through your musical sensibility.

The same goes for any “derivative” project. We just covered a tuning-fork-based clock that was a remake of a previous incarnation, but in the process of re-making, it morphed a little bit into something more aesthetically post-apocalyptic. We’ve seen possibly a million word clock builds, but [t0mg]’s version this one is beautifully laser-etched into paint on the back side of glass, and made me think that you could do the same with the coating on the back side of a mirror. Riffing. I could go on for hours.

So maybe it’s not as sexy to re-make someone else’s project, but it can be tremendously valuable. It’s how we learn tools, how we increase our creative vocabulary, and it gives us a chance to explore something cool that someone else has done from the inside out. Copying should be seen as essential skill-building, despite our cultural prejudices against it. Go out and print yourself some Yoda Heads (metaphorically) without shame!

source https://hackaday.com/2021/02/27/printing-yoda-heads-re-makers-riffing/

Printing Yoda Heads: Re-Makers Riffing!

We had a comment recently from a nasty little troll (gasp! on the Internet!). The claim was that most makers are really just “copiers” because they’re not doing original work, whatever that would mean, but instead just re-making projects that other people have already done. People who print other peoples’ 3D models, or use other peoples’ hardware or software modules are necessarily not being creative. Debunking a cheap troll isn’t enough because, on deeper reflection, I’m guilty of the same generic sentiment; that feeling that copying other people’s work isn’t as worthy as making your own. And I think that’s wrong!

In the 3D printing world in particular, I’m guilty of dismissively classifying projects as “Yoda Heads”. About ten years ago, [chylld] uploaded a clean, high-res model of Yoda to Thingiverse, and everyone printed it out. Heck, my wife still has hers on her desk; and alone this is proof that straight-up copying has worth, because it made a sweet little gift. After a while, Yoda gave way to Baby Groots, and strangely enough we’re back to Yoda again, but it’s Baby Yoda now.

Does filling the world with more Yoda Heads, vomiting toothpaste or not, further creativity? I’d argue it does. It’s actually a moderately difficult print — those spindly little ears present an overhang challenge that’ll definitely help you calibrate your cooling, or force you to learn something about supports. Pushing your limits in 3D printing teaches you about the tool and what possibilities it presents. Mastering a tool is an important step toward using it creatively. And then there’s “riffing”.

Jazz musicians don’t just get up and play improvisational solos that come magically into their heads. They’ve spent hours in the shed, copying the ways that other players have interpreted the classics. Which is to say, they become creative through copying. Transcendental, inspirational, original moments come about through hours and hours of filtering other peoples’ work through your fingers, ears, and lips until it becomes a part of you and eventually bubbles up through your musical sensibility.

The same goes for any “derivative” project. We just covered a tuning-fork-based clock that was a remake of a previous incarnation, but in the process of re-making, it morphed a little bit into something more aesthetically post-apocalyptic. We’ve seen possibly a million word clock builds, but [t0mg]’s version this one is beautifully laser-etched into paint on the back side of glass, and made me think that you could do the same with the coating on the back side of a mirror. Riffing. I could go on for hours.

So maybe it’s not as sexy to re-make someone else’s project, but it can be tremendously valuable. It’s how we learn tools, how we increase our creative vocabulary, and it gives us a chance to explore something cool that someone else has done from the inside out. Copying should be seen as essential skill-building, despite our cultural prejudices against it. Go out and print yourself some Yoda Heads (metaphorically) without shame!

source https://hackaday.com/2021/02/27/printing-yoda-heads-re-makers-riffing/

Printing Yoda Heads: Re-Makers Riffing!

We had a comment recently from a nasty little troll (gasp! on the Internet!). The claim was that most makers are really just “copiers” because they’re not doing original work, whatever that would mean, but instead just re-making projects that other people have already done. People who print other peoples’ 3D models, or use other peoples’ hardware or software modules are necessarily not being creative. Debunking a cheap troll isn’t enough because, on deeper reflection, I’m guilty of the same generic sentiment; that feeling that copying other people’s work isn’t as worthy as making your own. And I think that’s wrong!

In the 3D printing world in particular, I’m guilty of dismissively classifying projects as “Yoda Heads”. About ten years ago, [chylld] uploaded a clean, high-res model of Yoda to Thingiverse, and everyone printed it out. Heck, my wife still has hers on her desk; and alone this is proof that straight-up copying has worth, because it made a sweet little gift. After a while, Yoda gave way to Baby Groots, and strangely enough we’re back to Yoda again, but it’s Baby Yoda now.

Does filling the world with more Yoda Heads, vomiting toothpaste or not, further creativity? I’d argue it does. It’s actually a moderately difficult print — those spindly little ears present an overhang challenge that’ll definitely help you calibrate your cooling, or force you to learn something about supports. Pushing your limits in 3D printing teaches you about the tool and what possibilities it presents. Mastering a tool is an important step toward using it creatively. And then there’s “riffing”.

Jazz musicians don’t just get up and play improvisational solos that come magically into their heads. They’ve spent hours in the shed, copying the ways that other players have interpreted the classics. Which is to say, they become creative through copying. Transcendental, inspirational, original moments come about through hours and hours of filtering other peoples’ work through your fingers, ears, and lips until it becomes a part of you and eventually bubbles up through your musical sensibility.

The same goes for any “derivative” project. We just covered a tuning-fork-based clock that was a remake of a previous incarnation, but in the process of re-making, it morphed a little bit into something more aesthetically post-apocalyptic. We’ve seen possibly a million word clock builds, but [t0mg]’s version this one is beautifully laser-etched into paint on the back side of glass, and made me think that you could do the same with the coating on the back side of a mirror. Riffing. I could go on for hours.

So maybe it’s not as sexy to re-make someone else’s project, but it can be tremendously valuable. It’s how we learn tools, how we increase our creative vocabulary, and it gives us a chance to explore something cool that someone else has done from the inside out. Copying should be seen as essential skill-building, despite our cultural prejudices against it. Go out and print yourself some Yoda Heads (metaphorically) without shame!

source https://hackaday.com/2021/02/27/printing-yoda-heads-re-makers-riffing/

A Very Modern Tube Headphone Amplifier

Once a discarded relic, over the years the humble vacuum tube has been rehabilitated in the arena of specialist audio. There are plenty of tube amplifiers now being manufactured, with a popular choice being headphone amplifiers that use a tube as a gain stage followed by an op-amp as a buffer with a low impedance output. This forms the basis of [Ratti3]’s amplifier, but with the added interest of a battery supply and a Bluetooth connection.

The tube circuit is a very conventional anode follower using an EF95 pentode. This provides plenty of gain and of course that “valve sound” beloved of audio enthusiasts, but suffers from an output impedance too high to drive a set of headphones. An NE5532 steps in for the op-amp buffer role, making for a very simple circuit. Power comes from a set of four 18650 Lithium-Ion cells with associated charger and balance boards, while a little switching boost converter provides the 100 volt HT for the tubes.

We’ve visited this type of amplifier before with a similar but much more rough-around-the-edges Chinese version. That had some astonishingly cheap Chinese tubes, but if we’re seeking better components it’s interesting to know just who makes tubes these days.

source https://hackaday.com/2021/02/27/a-very-modern-tube-headphone-amplifier/

Sounding the Humble LED

Here at Hackaday we’re no strangers to the colorful glow of LEDs. But what if there was more to appreciate beneath the surface? Back in 2011 [Windell] over at Evil Mad Scientist dug into a certain variety of LED and discovered they had a song to sing.

Over the last couple decades, you’ve likely encountered the flickering “candle flame” variety of LED. Often found embedded in small plastic candle simulacra they are shaped like typical through hole “gumdrop” style LEDs, but pack some extra magic which causes them to flicker erratically. Coupled with a warm white color temperature the effect isn’t entirely dissimilar to the flickering of a candle flame.

To the Hackaday reader (and [Windell]) the cause of the flickering may be fairly clear, there is an IC embedded in the lens of the LED. See photo at top for an example of how this might look, helpfully magnified by the lens of the LED itself. Looking through the lens the captive die is visible, as well as the bond wires connecting it to the legs and light emitting diode itself. [Windell]’s observation is that together this assembly makes for a somewhat strange electrical component; from the perspective of the circuit it appears to randomly vary the current flowing through the LED.

He includes two interesting demos. One is that by attaching the flickering LED to a BJT he can turn it into a current amplifier and successfully drive a much more powerful 1W LED with the same effect. The other is that  with the power of the amplifier the same flickering LED can drive a buzzer as well. The effect is surprisingly pleasant, though we’d hesitate to call it musical.

For a more recent example of a similar phenomenon with a very different sound, check out out [Emily Velasco]’s playback of a similarly constructed RGB color changing LED, embedded below. We’ve seen optical tools used to decode LED flickers into data streams, but not for audio playback! We have also covered some LED flicker reverse engineering that spills more of the mystery sealed up in these specialized diodes.

source https://hackaday.com/2021/02/27/sounding-the-humble-led/

Bottle Filler Perfectly Tops Your Cup

You know those bottle fillers at schools and airports? What if you had one of those at home?

We know what you’re going to say: “My fridge has one of those!” Well ours doesn’t, and even though [Chris Courses’] fridge did, his bottle of choice didn’t fit in the vertically-challenged water and ice hutch, nor did it fill autonomously. The solution was to build a dubiously placed, but nonetheless awesome custom bottle filler in his kitchen.

The plumbing for the project couldn’t be more straight-forward: a 5-year undersink water filter, electronically actuated valve, some tubing, and a T to splice into the existing water line going to the fridge. Where the rubber hits the road is making this look nice. [Chris] spends a lot of time printing face plates, pouring resin as a diffuser, and post processing. After failing on one formulation of resin, the second achieves a nice look, and the unit is heavily sanded, filled, painted, prayed over, and given the green light for installation.

For the electronics [Chris] went for a Raspberry Pi to monitor four buttons and dispense a precise allotment tailored to each of his favorite drinking vessels. While the dispenser is at work, three rows of LEDs play an animated pattern. Where we begin to scratch our heads is the demo below which shows there is no drain or drip tray below the dispenser — seems like an accident waiting to happen.

Our remaining questions are about automating the top-off process. At first blush you might wonder why a sensor wasn’t included to shut off the filler automatically. But how would that work? The dispenser needs to establish the height of the bottle and that’s a non-trivial task, perhaps best accomplished with computer vision or a CCD line sensor. How would you do it?

source https://hackaday.com/2021/02/26/bottle-filler-perfectly-tops-your-cup/

Bottle Filler Perfectly Tops Your Cup

You know those bottle fillers at schools and airports? What if you had one of those at home?

We know what you’re going to say: “My fridge has one of those!” Well ours doesn’t, and even though [Chris Courses’] fridge did, his bottle of choice didn’t fit in the vertically-challenged water and ice hutch, nor did it fill autonomously. The solution was to build a dubiously placed, but nonetheless awesome custom bottle filler in his kitchen.

The plumbing for the project couldn’t be more straight-forward: a 5-year undersink water filter, electronically actuated valve, some tubing, and a T to splice into the existing water line going to the fridge. Where the rubber hits the road is making this look nice. [Chris] spends a lot of time printing face plates, pouring resin as a diffuser, and post processing. After failing on one formulation of resin, the second achieves a nice look, and the unit is heavily sanded, filled, painted, prayed over, and given the green light for installation.

For the electronics [Chris] went for a Raspberry Pi to monitor four buttons and dispense a precise allotment tailored to each of his favorite drinking vessels. While the dispenser is at work, three rows of LEDs play an animated pattern. Where we begin to scratch our heads is the demo below which shows there is no drain or drip tray below the dispenser — seems like an accident waiting to happen.

Our remaining questions are about automating the top-off process. At first blush you might wonder why a sensor wasn’t included to shut off the filler automatically. But how would that work? The dispenser needs to establish the height of the bottle and that’s a non-trivial task, perhaps best accomplished with computer vision or a CCD line sensor. How would you do it?

source https://hackaday.com/2021/02/26/bottle-filler-perfectly-tops-your-cup/

The Famous Basic Computer Games Book Gets a 2021 Update

If you are a certain age, your first programming language was almost certainly BASIC. You probably at least saw the famous book by Ahl, titled BASIC Computer Games or 1010 BASIC Computer Games. The book, published in 1973 by [David Ahl] was a staple in its day and the first computer book to sell over one million copies. Of course, if you want to run Super Star Trek or Hamurabi, you better fire up an old retrocomputer or a simulator because BASIC in 1973 doesn’t look like what we have today. Or, you can head to GitHub where [coding-horror] is inviting people to help update the programs using modern languages.

One of our favorites, Bagels, is there with directories for C#, Java, Javascript, Python, Ruby, and VB.net. It doesn’t appear that all of the games are in all the languages, though. There’s also a .Net solution file that apparently has a few entries in it. We were also happy to see Super Star Trek represented, along with a link to an article about a C++ language port. The original games were tweaked to run on VintageBasic.

By today’s standards, these games are pretty crude, but they are still engaging and, if you remember them, always nostalgic.  There is one thing missing, though. In 1973, you had no choice but to type the programs in yourself. You couldn’t help but learn something about programming in the process. Besides, you then had to debug the program to find your typing mistakes and that was definitely educational. It might seem like these games are ultra-simple, but hexapawn does machine learning and the lunar lander game is a simple physics simulation.

Regardless of language, if I were using these with a student, I might be tempted to make them type the programs in by hand. They’d probably revolt against the idea, but it might be good training. Think of “wax on, wax off” from the Karate Kid.

Seeing some of these old gems is like unexpectedly running into an old friend. If you want to help out, there’s a discussion board available. You’d think BASIC would be gone by now, but it still hangs in there. If your program is short enough, you might even run it on Twitter.

source https://hackaday.com/2021/02/26/the-famous-basic-computer-games-book-gets-a-2021-update/

3D Printed Printing Press Turns You into Gutenberg

A few machines have truly changed the world, such as the wheel, steam engines, or the printing press. Maybe 3D printers will be on that list one day too. But for today, you can use your 3D printer to produce a working printing press by following plans from [Ian Mackay]. The machine, Hi-Bred, allows you to place printed blocks in a chase — that’s the technical term — run a brayer laden with ink over the type blocks and hand press a piece of paper with the platen.

The idea is more or less like a giant rubber stamp. As [Ian] points out, one way to think about it is that white pixels are 0mm high and black pixels are 3mm high. He suggests looking at old woodcuts for inspiration.

This might be just the thing for doing something fancy like custom invitations. Seems like it would be pretty hard to do a booklet or magazine, although anything is possible if you are patient. Real type was made with lead and we doubt the plastic type will be quite as durable.

Of course, if you just want the old school feel, you could try a mimeograph or hectograph. In the old days, typesetter put type in from big cases that often wind up now as shadowboxes. But then came the Linotype.

source https://hackaday.com/2021/02/26/3d-printed-printing-press-turns-you-into-gutenberg/

Spectrogram Drawing For Fun And Coding

It probably can’t have taken long after the first spectrum waterfall display was created, before somebody had a go at creating a waveform that would create an image in the waterfall. We don’t know who that pioneer was, but it’s over 20 years since Aphex Twin famously used the technique in their music, so it’s nothing new. If you fancy a go for yourself, [Gokberk Yaltirakli] has the project for you, creating waterfall images with an SDR from image files, using a bit of Python code.

The value here isn’t necessarily in creating the waterfall of Bitcoin logos that can be seen in the video he’s put on the page, instead it’s in the simple explanation of creating I and Q values for an SDR. The code is a bit slow so writes its values to a file which is output by a HackRF, but it could just as easily be used by any other capable output device such as GNU Radio and a soundcard if you too want an Aphex Twin moment. The hardware for displaying a spectrum waterfall doesn’t even have to be very complex.

Thanks [Leo] for the tip.

source https://hackaday.com/2021/02/26/spectrogram-drawing-for-fun-and-coding/

This Week in Security: Mysterious Mac Malware, An Elegant VMware RCE, and a JSON Mess

There’s a new malware strain targeting MacOS, Silver Sparrow, and it’s unusual for a couple reasons. First, it’s one of the few pieces of malware that targets the new M1 ARM64 processors. Just a reminder, that is Apple’s new in-house silicon design. It’s unusual for a second reason — it’s not doing anything. More precisely, while researchers have been watching, the command and control infrastructure didn’t provide a payload. Silver Sparrow has been positively found on nearly 30,000 machines.

The malware also has an intentional kill switch, where the presence of a particular file triggers a complete removal of the malware package. Researchers at Red Canary point out that this package behaves very much like a legitimate program, difficult to pick out as malware. Ars Technica got an off-the-record statement from Apple, indicating that they are tracking the situation, and have revoked the developer’s certificate used to sign the malware. It’s not entirely clear whether this prevents the malware running on already compromised machines, or just stops new infections.

So who’s behind Silver Sparrow? The observed stealth mode and other complexities suggest that this is more than a simple adware or ransomware campaign. Since it was discovered before the payload was delivered, we may never know what the purpose is. It may have been a government created campaign, targeting something specific.

VMware RCE

The details of a VMware vulnerability were published this week, and the attack struck me as rather elegant. CVE-2021-21972 is a combination of two problems. The first is that the VMware web interface exposes an HTTP endpoint that doesn’t enforce user authentication. One of the functions of this endpoint is to allow the upload of an archive file, and extract this in the /tmp directory. The second problem is that the extraction function didn’t properly sanitize the names of the extracted files. Hence, it was possible to create an archive with a path transversal attack.

Here we have two very simple flaws, and when put together, allow a completely unauthenticated actor to easily get arbitrary code execution on the machine running VMware. The attack works on Linux and Windows servers, with expected implementation variations.

Inside a Wireless Security System

Ever wonder just how secure a residential security system is? [Nick Miles] and [Chris Lyne], a pair of researchers from Tenable, wondered the same thing, and decided to tear apart a SimpliSafe system, wringing out all of its secrets. They started with logic analyzers, and went as far as paying for functional decapping of the chips, to recover the firmware.

The step-by-step process is worth reading, but the conclusion is that the system is relatively well put together. Each device has an immutable AES key, and that represents an attack surface that wouldn’t be present with a more robust key exchange.

For the curious, [Nick] did a detailed analysis of a Ring system just a few months back.

Proper Exploit Attribution, The Story of Jian

I’ve been known to be a bit skeptical when an attack or exploit is attributed to a foreign nation, but no real evidence is presented. A story caught my eye this week, because it’s a wonderful example of what proper attribution looks like, not to mention a great example of unraveling a malware mystery. Check Point Research looked deep into an exploit used by APT31, believed to be a part of the Chinese government.

There are way too many details to dive into here, go read the post for the particulars, but we’ll cover the high points. Remember the Shadow Brokers leak, back in 2017? That was a collection of impressive 0-days that is universally recognized as produced by the Equation Group, part of the NSA. One of the tools exposed in that lead was “EpMe”, which leveraged CVE-2017-0005. Jian, an exploit produced by APT31 also targeted this CVE, and was probably created in 2014.

The kicker here is that Checkpoint makes a very convincing case that it was no accident that both exploits targeted the same CVE, but that the Chinese exploit was based on a captured sample of the NSA-produced tool. Essentially, they reverse-engineered the exploit and used it in their own operations, even before the tool was exposed by the Shadow Brokers.

Firefox State Partitioning

Allow cross-site cookiesMozilla has released a new privacy feature, State Partitioning, a way to authoritatively stop cookie-based tracking online. The concept is deceptively simple. Every domain you visit has its own “cookie jar”. Many websites have Facebook iframes or embedded images. State partitioning would isolate the cookies created by each of those iframes, meaning your browser is anonymous to Facebook on each of those sites.

Hand-in-hand is a new API that allows a website to request cross-site cookie access. This is important for the handful of uses where access is needed for legitimate uses, like Single Sign-On services. For now, partitioning is off by default, and can be turned on via the Enhanced Tracking Protection strict setting.

JSON Undefined Behavior

[Jake Miller] of Bishop Fox Labs wrote a great intro to a subject I’ve never considered: odd JSON constructions, and how different implementations handle them. An example will help.


obj = {"test": 1, "test": 2}

So what’s the value of obj["test"]? It’s complicated. Some JSON parsers will choose the first definition of a key, while others choose the last. Still others will throw an error in response. What makes this a particularly serious problem is that the same data may be parsed by different implementations in a single transaction. The example given in the post is of an online store, where the payment processing is handled by a third party.

The attack works by manipulating the JSON object sent by the browser, injecting a second value definition for the quantity of items purchased. The store itself sees the higher value, which determines the actual items shipped. The payment backend uses a different JSON parser, which sees the smaller value. The backend actually handles payment processing, so the amount charged is that of the smaller quantity.

The article goes on to describe issues with invalid unicode embedded in JSON and valid keypairs that have been /*commented out*/, and what happens when you re-serialize this quirky data. Another interesting edge case is the handling of very large numbers, where some parsers return 0, others return a null, and some an approximation in scientific notation.

All told, JSON deserialization is a mess. There’s sure to be many hard-to-spot bugs in web applications that use multiple parsers. The author makes a few recommendations at the end of the post. The most important is that parsers should produce a fatal error on particular quirky JSON input, rather than returning a guess at what data was intended.

source https://hackaday.com/2021/02/26/this-week-in-security-mysterious-mac-malware-an-elegant-vmware-rce-and-a-json-mess/

Should I Use Wheels Or Tracks?

When it comes to dominating offroad performance, many people’s first thought is of tracked vehicles. Bulldozers, tanks and excavators all use treads, and manage to get around in difficult terrain without breaking a sweat. Today, we’re exploring just what makes tracked vehicles so capable, as well as their weaknesses.

It’s All About Ground Pressure

The various parts of a tank’s propulsion system.

Let’s first look at how tank tracks work. There are a huge variety of designs, with differences depending on application. Different trends have been followed over time, and designs for military use in combat differ from those used for low-speed construction machines, for example. But by looking at a basic tank track design, we can understand the basic theory. On tanks, the track or tread itself is usually made up of individual steel links that are connected together with hinges, though other machines may use rubber tracks instead. The tracks are wrapped around one or more drive wheels, often cogged, which directly pull on the track. On the bottom of the vehicle are the road wheels, which ride on top of the track where it lies on the ground.  The weight of the vehicle is carried through the road wheels and passed on to the tread, spreading out the load across a broader area. Outside of this, the track system may also have one or more idler wheels used to keep the track taught, as well as return rollers to guide the track back around without touching the road wheels.

The low ground pressure of tracks, thanks to their large contact patch, means they’re perfect for driving in soft terrain like sand without sinking in.

Tank tracks, or continuous tracks as they’re more technically known, were developed initially for farm and logging applications, for heavy vehicles that needed to operate in soft terrain. Continuous treads had the advantage that they could support a vehicle’s weight over a much greater area than wheels. Spreading out the load meant that the ground pressure was lower, and thus the vehicle was less likely to sink into soft mud or sand. It also allowed a vehicle to put much more torque to the ground without slipping, thanks to the much larger contact patch compared to regular wheels. The party piece of the tank — the ability to crush smaller road vehicles — is as much a result of its huge weight as its tracks. However, the tracks are less likely to get tangled or damaged when driving over another vehicle, compared to a pneumatic tyre.

Awful Highway Mileage

When it comes to high speed travel on road surfaces, wheels are a far more efficient and comfortable solution.

However, tracks come with drawbacks that make them unsuitable for many applications. There’s a reason you don’t see tanks taking people to work on the New Jersey Turnpike; if you did you’d probably assume something political had gone very, very wrong. For many vehicular applications, the simple pneumatic tyre and wheel combination is more suitable. Pneumatic tyres do less damage to paved surfaces than tracks, and are better suited to higher speed operation. They’re also less noisy, and far easier to replace when damaged. Tracks are significantly more mechanically complicated, with the average tank having many more wheels and moving parts, as well as the tracks themselves. All of these add some loss to the driveline, making tracked transport far less fuel efficient, too. Steering on tracked vehicles can also be complicated for single-engine setups, requiring special gear mechanisms to allow the speed of each tread to be varied appropriately. Additionally, while tracks are great on soft surfaces, they don’t offer anything particularly special when it comes to ground clearance. In many cases, a properly designed wheeled vehicle may out perform a tracked one in a rock-crawling scenario.

Tracks as a Drive Train

For robots doing delicate work, tracks can be a good solution, providing the ability to turn on a coin and accurately manoeuvre in tight spaces.

Tracks are also used on smaller scale vehicles, from robots to radio controlled toys. Here, they maintain the benefits of lower ground pressure compared to wheels. However, the often lower weight of smaller scale vehicles means this isn’t as much of a benefit as it is for a main battle tank that must carry up to 60 tons of armour and weaponry into battle. Smaller scale vehicles that run on electricity can have the benefit of running one motor per track however, eliminating much of the steering complexity in single-engine vehicles. Much like larger vehicles, while tracks may offer better performance in soft surfaces, ground clearance is still important for dealing with obstacles like rocks.

Overall, it’s important to remember that tracks were designed to do one thing well, and that’s get vehicles through soft, boggy terrain like mud, snow and sand. If you’re having to deal with such conditions, the tank track might be just the engineering solution you’ve been looking for. If, however, high speed, efficiency, or comfort are more important – you’re probably best sticking with wheels!

source https://hackaday.com/2021/02/26/should-i-use-wheels-or-tracks/

Should I Use Wheels Or Tracks?

When it comes to dominating offroad performance, many people’s first thought is of tracked vehicles. Bulldozers, tanks and excavators all use treads, and manage to get around in difficult terrain without breaking a sweat. Today, we’re exploring just what makes tracked vehicles so capable, as well as their weaknesses.

It’s All About Ground Pressure

The various parts of a tank’s propulsion system.

Let’s first look at how tank tracks work. There are a huge variety of designs, with differences depending on application. Different trends have been followed over time, and designs for military use in combat differ from those used for low-speed construction machines, for example. But by looking at a basic tank track design, we can understand the basic theory. On tanks, the track or tread itself is usually made up of individual steel links that are connected together with hinges, though other machines may use rubber tracks instead. The tracks are wrapped around one or more drive wheels, often cogged, which directly pull on the track. On the bottom of the vehicle are the road wheels, which ride on top of the track where it lies on the ground.  The weight of the vehicle is carried through the road wheels and passed on to the tread, spreading out the load across a broader area. Outside of this, the track system may also have one or more idler wheels used to keep the track taught, as well as return rollers to guide the track back around without touching the road wheels.

The low ground pressure of tracks, thanks to their large contact patch, means they’re perfect for driving in soft terrain like sand without sinking in.

Tank tracks, or continuous tracks as they’re more technically known, were developed initially for farm and logging applications, for heavy vehicles that needed to operate in soft terrain. Continuous treads had the advantage that they could support a vehicle’s weight over a much greater area than wheels. Spreading out the load meant that the ground pressure was lower, and thus the vehicle was less likely to sink into soft mud or sand. It also allowed a vehicle to put much more torque to the ground without slipping, thanks to the much larger contact patch compared to regular wheels. The party piece of the tank — the ability to crush smaller road vehicles — is as much a result of its huge weight as its tracks. However, the tracks are less likely to get tangled or damaged when driving over another vehicle, compared to a pneumatic tyre.

Awful Highway Mileage

When it comes to high speed travel on road surfaces, wheels are a far more efficient and comfortable solution.

However, tracks come with drawbacks that make them unsuitable for many applications. There’s a reason you don’t see tanks taking people to work on the New Jersey Turnpike; if you did you’d probably assume something political had gone very, very wrong. For many vehicular applications, the simple pneumatic tyre and wheel combination is more suitable. Pneumatic tyres do less damage to paved surfaces than tracks, and are better suited to higher speed operation. They’re also less noisy, and far easier to replace when damaged. Tracks are significantly more mechanically complicated, with the average tank having many more wheels and moving parts, as well as the tracks themselves. All of these add some loss to the driveline, making tracked transport far less fuel efficient, too. Steering on tracked vehicles can also be complicated for single-engine setups, requiring special gear mechanisms to allow the speed of each tread to be varied appropriately. Additionally, while tracks are great on soft surfaces, they don’t offer anything particularly special when it comes to ground clearance. In many cases, a properly designed wheeled vehicle may out perform a tracked one in a rock-crawling scenario.

Tracks as a Drive Train

For robots doing delicate work, tracks can be a good solution, providing the ability to turn on a coin and accurately manoeuvre in tight spaces.

Tracks are also used on smaller scale vehicles, from robots to radio controlled toys. Here, they maintain the benefits of lower ground pressure compared to wheels. However, the often lower weight of smaller scale vehicles means this isn’t as much of a benefit as it is for a main battle tank that must carry up to 60 tons of armour and weaponry into battle. Smaller scale vehicles that run on electricity can have the benefit of running one motor per track however, eliminating much of the steering complexity in single-engine vehicles. Much like larger vehicles, while tracks may offer better performance in soft surfaces, ground clearance is still important for dealing with obstacles like rocks.

Overall, it’s important to remember that tracks were designed to do one thing well, and that’s get vehicles through soft, boggy terrain like mud, snow and sand. If you’re having to deal with such conditions, the tank track might be just the engineering solution you’ve been looking for. If, however, high speed, efficiency, or comfort are more important – you’re probably best sticking with wheels!

source https://hackaday.com/2021/02/26/should-i-use-wheels-or-tracks/

Should I Use Wheels Or Tracks?

When it comes to dominating offroad performance, many people’s first thought is of tracked vehicles. Bulldozers, tanks and excavators all use treads, and manage to get around in difficult terrain without breaking a sweat. Today, we’re exploring just what makes tracked vehicles so capable, as well as their weaknesses.

It’s All About Ground Pressure

The various parts of a tank’s propulsion system.

Let’s first look at how tank tracks work. There are a huge variety of designs, with differences depending on application. Different trends have been followed over time, and designs for military use in combat differ from those used for low-speed construction machines, for example. But by looking at a basic tank track design, we can understand the basic theory. On tanks, the track or tread itself is usually made up of individual steel links that are connected together with hinges, though other machines may use rubber tracks instead. The tracks are wrapped around one or more drive wheels, often cogged, which directly pull on the track. On the bottom of the vehicle are the road wheels, which ride on top of the track where it lies on the ground.  The weight of the vehicle is carried through the road wheels and passed on to the tread, spreading out the load across a broader area. Outside of this, the track system may also have one or more idler wheels used to keep the track taught, as well as return rollers to guide the track back around without touching the road wheels.

The low ground pressure of tracks, thanks to their large contact patch, means they’re perfect for driving in soft terrain like sand without sinking in.

Tank tracks, or continuous tracks as they’re more technically known, were developed initially for farm and logging applications, for heavy vehicles that needed to operate in soft terrain. Continuous treads had the advantage that they could support a vehicle’s weight over a much greater area than wheels. Spreading out the load meant that the ground pressure was lower, and thus the vehicle was less likely to sink into soft mud or sand. It also allowed a vehicle to put much more torque to the ground without slipping, thanks to the much larger contact patch compared to regular wheels. The party piece of the tank — the ability to crush smaller road vehicles — is as much a result of its huge weight as its tracks. However, the tracks are less likely to get tangled or damaged when driving over another vehicle, compared to a pneumatic tyre.

Awful Highway Mileage

When it comes to high speed travel on road surfaces, wheels are a far more efficient and comfortable solution.

However, tracks come with drawbacks that make them unsuitable for many applications. There’s a reason you don’t see tanks taking people to work on the New Jersey Turnpike; if you did you’d probably assume something political had gone very, very wrong. For many vehicular applications, the simple pneumatic tyre and wheel combination is more suitable. Pneumatic tyres do less damage to paved surfaces than tracks, and are better suited to higher speed operation. They’re also less noisy, and far easier to replace when damaged. Tracks are significantly more mechanically complicated, with the average tank having many more wheels and moving parts, as well as the tracks themselves. All of these add some loss to the driveline, making tracked transport far less fuel efficient, too. Steering on tracked vehicles can also be complicated for single-engine setups, requiring special gear mechanisms to allow the speed of each tread to be varied appropriately. Additionally, while tracks are great on soft surfaces, they don’t offer anything particularly special when it comes to ground clearance. In many cases, a properly designed wheeled vehicle may out perform a tracked one in a rock-crawling scenario.

Tracks as a Drive Train

For robots doing delicate work, tracks can be a good solution, providing the ability to turn on a coin and accurately manoeuvre in tight spaces.

Tracks are also used on smaller scale vehicles, from robots to radio controlled toys. Here, they maintain the benefits of lower ground pressure compared to wheels. However, the often lower weight of smaller scale vehicles means this isn’t as much of a benefit as it is for a main battle tank that must carry up to 60 tons of armour and weaponry into battle. Smaller scale vehicles that run on electricity can have the benefit of running one motor per track however, eliminating much of the steering complexity in single-engine vehicles. Much like larger vehicles, while tracks may offer better performance in soft surfaces, ground clearance is still important for dealing with obstacles like rocks.

Overall, it’s important to remember that tracks were designed to do one thing well, and that’s get vehicles through soft, boggy terrain like mud, snow and sand. If you’re having to deal with such conditions, the tank track might be just the engineering solution you’ve been looking for. If, however, high speed, efficiency, or comfort are more important – you’re probably best sticking with wheels!

source https://hackaday.com/2021/02/26/should-i-use-wheels-or-tracks/

DIY All-Transistor Addressable Pixel

By now most readers should be used to addressable LEDs, devices that when strung out in a connected chain can be individually lit or extinguished by a serial data stream. Should you peer at one under a microscope you’ll see alongside the LED dies an integrated circuit that handles all the address decoding. It’s likely to be quite a complex device, but how simply can its functions be replicated? It’s a theme [Tim] has explored in the TransistorPixel, and addressable LED board that achieves addressability with only 17 transistors.

It uses a surprisingly straightforward protocol, in which a pulse longer than 500ns enables the LED while a shorter one turns it off. Subsequent pulses in a train are passed on down the line to the next device. A 20µs absence of a pulse resets the string and sets it to wait for the next pulse train. Unlike the commercial addressable LEDS there is only a single colour and no suport for gradated brightness, but it’s still an impressive circuit.

Under the hood is some very old-school RTL logic, a monostable to detect the pulse and a selection of gates and a latch to capture the state and forward to the chain. It’s laid out on a PCB in order of circuit function, and while we can see that maybe it’s not a practical addresssable LED for 2021, it’s likely that it could be made into a much smaller PCB if desired.

Perhaps unsurprisingly given the ready availability of addressable LEDs, we’ve not seen many home made ones. This addressable 7-segment display may be the closest.

source https://hackaday.com/2021/02/26/diy-all-transistor-addressable-pixel/