Direct FDM Printing With Granules

The idea of FDM 3D printing using granules rather than filament is an appealing one: rather than having to wrangle spools of filament that need to adhere to strict dimensions and cannot be too flexible, you can instead just keep topping up a big hopper with fresh granules. This is what [HomoFaciens] has been tinkering with for a while now, with their Direct Granules Extruder V7.0 showing significant improvements.

There’s also an accompanying article, with details of previous granule extruder attempts detailed on the same site. Many of the improvements here focus on making sure the granules melt properly before they reach the end of the extruder, with the auger screw helping to push things along. While this seems straightforward, there are many details to get right, with the previous v6.2 version having issues like the hot plastic backing up into the cold section and clogging things up.

For the test bench a Prusa Mk4 FDM printer is used, with the standard extruder swapped for the experimental extruder. On the extruder the cold, top part is water cooled to ensure it stays cold, with each turn of the wood-screw-turned-auger providing the right extrusion speed. As can be seen with the print tests, the results look pretty good despite the extruder not having been tuned yet.

If you want to give it a shot yourself, the article page provides files for download.

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Why Opposed Piston Internal Combustion Engines Are Great

Converting the ignition of a fuel-air mixture into usable mechanical energy lies at the core of a dizzying number of internal combustion engines developed over the course of more than century. Although typical piston engines with a cylinder head and valve-train are the most common by far, and even rotary engines are quite well-known, the opposed-piston engine design is significantly more obscure. In a recent video by [driving 4 answers], this type of engine is covered and why it’s actually a pretty nifty ICE design with many benefits.

Achates opposed-piston design. (Source: driving 4 answers, YouTube)
Achates opposed-piston design. (Source: driving 4 answers, YouTube)

Above all, the design is mechanically far more simple, as it omits all the valves and timing-related hardware of the typical four-stroke ICE. Each ignition event pushes against two pistons at the same time, allowing for more of the kinetic energy to be converted into usable power, as well as enabling largely vibration-free operation in a more compact package, especially in the case of the Asender design that eliminates the second crankshaft of the Achates design. This makes the Asender rather similar to the 1914 Simpson’s design.

Despite these many advantages, opposed-piston engines have mostly led a quiet life in industrial and military applications, including tanks, submarines and airplanes. This is where the video also sees their continued use, but as a 2021 article in Autoweek suggests, we might be seeing more of these engines in everywhere from trucks to cars as well. Even if it’s only in hybrid cars where it would be in a generator role, there are many reasons why this ICE design would fit right into certain roles.

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Using Hamster Power To Charge A Phone

It seems fair to say that hamsters are a somewhat divisive pet, between their fluffiness, high-strung nature, short lifespan and incessant squeaking that sounds like some electronic device is trying to tell you something. With that in mind, maybe that having these fuzzy little critter take up some of the daily slack will help endear them to more people. Something like helping to charge mobile devices by converting their frantic exercise wheel time into electrical power. Cue [Flamethrower]’s hamster wheel-powered generator.

Due to the irregular pacing of the hamster on its wheel it makes sense to treat it as an energy harvesting problem, for which the common CJMCU-2557 module – featuring the TI BQ25770 – is a pretty good option. It covers a voltage input from 0.1 – 5.1 V after a cold start minimum of 0.6 V, with a maximum current of 0.1 A.

The modules come with a super capacitor to store collected energy, but you can further charge a connected battery, for which [Flamethrower] used salvaged 18650 Li-ion cells. After letting the hamster do its thing for a night in the – admittedly far too small wheel –  there’s enough power in the cell to at least start charging a smartphone, though sadly it’s not mentioned how much power was harvested.

Hopefully the hamster in question will be overclocked with a larger wheel, along with detailed measurements of how many hamsters it takes to charge the average phone.

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Defeating The [Works By Design]’s Unpickable Lock

Even though the very concept of an ‘unpickable lock’ is as plausible as making water not be wet, this doesn’t take away from the intellectual thrill of devising solutions to picking attacks and subsequently circumventing those solutions. Case in point the ‘unpickable’ traveling key lock that [Works by Design] recently featured and sent a few copies off to lock pickers such as [Lock Noob] who gave picking it a shake.

Many of the details and reasoning behind [Works by Design]’s lock design can be found in the original video, with [Lock Noob] going over the basic summary before getting to work trying to pick it.

Rather than trying to bump the tumbler lock mechanism or another indirect approach, the focus is here on an impressioning attack. Although in this traveling key mechanism the physical key is moved inside the lock, the pins of the tumbler lock will leave impressions on the brass blanks when the lock is gently forced to rotate, indicating that there’s still too much material there.

The approach here is thus to slowly file away these sections, with interestingly the plastic pin that [Works by Design] had added to dodge impressioning attacks not being too much of an issue. Thus after over an hour of turning-filing-turning-filing ad nauseam, the lock mechanism rotated, confirming that it had been defeated.

In the subsequent teardown of the lock it can be seen that a plastic pin is indeed rather fragile, with part of its top having been torn off. After replacing this damaged plastic pin with a fresh one, a foil-based impressioning attack is attempted by putting aluminium foil over a skeleton key, but this didn’t quite work out as the pins come in sideways and thus do not leave a useful impression.

Theoretically the pins would press down onto the soft foil, creating an almost immediate impression of the required key. Perhaps that leaving a solid side on the blank would make it work, but this is an approach that would have to be refined.

Either way, it shows that ‘unpickable’ depends on your definition, as ‘1+ hour of filing with knowledge of bitting depths’ would be considered ‘unpickable’ by some. At least it’s not as dramatic as a 2020 [Stuff Made Here] ‘unpickable lock’ hack that we covered, before it got shredded by the [LockPickingLawyer] with resulting list of potential fixes of multiple easy exploits before even having to resort to impressioning.

Considering that traveling key designs generally require at least a tedious impressioning attack, with potential ways to address this in a more substantial way, a redesign featuring these changes would be rather interesting to see picked. If it can defeat the average lockpicking enthusiast including those practicing the legal profession, it’s probably as close to ‘unpickable’ as can be before the bolt cutters and angle grinders are used against any vulnerable parts that aren’t the lock itself.

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Using NFC To Power Devices Instead Of Qi

It shouldn’t be any surprise that NFC and similar RFID implementations are capable of providing power to a receiver, since this is after all how RFID tags can work without a battery. The question is more whether you can do more with NFC than just briefly power some low-power circuitry to spit out some data. This is the topic of a recent [Denki Otaku] video.

Although both Qi and NFC use electromagnetic induction, they differ in the frequency and correspondingly the maximum power that they can deliver to a receiver. For NFC this is around a Watt, with the used NFC module supporting up to 250 mW, which already sets the rough scope of what one can expect from an NFC-powered device. That said, an NFC transmitter and receiver can be significantly smaller than those for Qi due to the much higher frequency.

An additional benefit of NFC is that it offers more freedom to the user in its protocol in terms of user data, which is useful for applications where you don’t just want to power a device. In the video an MCU and IMU are powered along with an OLED display, which demonstrates wireless charging as well as data transfer of the IMU data to a second MCU.

The benefits of NFC over Qi would thus be the smaller antenna size, and depending on the used NFC implementation also charging and data transfer at the same time.

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The Math You Need To Start Understanding LLMs

Once you peel back the hype and mysticism, large language models (LLMs) are a fascinating application of statistical models, effectively what you get when you dial a basic auto-complete model up to eleven. In order to analyze a mind-boggling amount of text and produce meaningful auto-completion results quite a bit of math is involved, with a recent three-part article series by [Giles] going through the basics of inference, being the prediction step using a trained model.

The text is encoded in the LLM’s vector space as token IDs, each token being a text fragment that has some probability of following another ID, such as when cats may be found on desks, as in the above photo by [Giles]. With inference multiple of such IDs are retrieved in a vector from which in successive steps a sentence can be pieced together. These so-called logits are detailed in the first article in the series, with the second article focusing on vocabulary space and embedding, as well as the matrix operations used for inference.

Finally, the third article puts all of this together and looks at transformers, which is a crucial part of GPT (generative pretrained transformer) LLM architecture. Of note is the attention mechanism, which takes GPTs beyond merely being glorified auto-complete systems by adding pattern matching. Here we can see how the statistical model of the LLM is used to generate a rather plausible output, which is where the human has to ask themselves in how far they feel that it is correct.

Of course, there goes a lot more into making LLMs and GPTs performant, such as key-value caches that massively speed up inference.

Teardown Of A Shahed-136 Gimbaled Camera

The remains of a gimbal camera after its drone was shot down. (Credit: Le labo de Michel, YouTube)
The remains of a gimbal camera after its drone was shot down. (Credit: Le labo de Michel, YouTube)

The Iranian Shahed-136’s basic design has seen many changes and additions since Russia began using them, with some featuring interesting payloads such as cameras in a gimbal, making these drones useful for tasks like surveillance. Recently [Michel] got his hands one one such camera that was recovered from a shot-down drone in Ukraine, providing the opportunity for an in-depth look at what hardware is in these cameras.

The teardown thus covers the gimbal mechanism itself as well as the electronics and camera. First up is an Artix-7 FPGA-based board, followed by the range finder assembly. Unsurprisingly the camera feed handling is performed by an Hi3519 SoC, as this appears to be the off-the-shelf option you find all over on AliExpress and similar sites. There’s also an Artix-7 FPGA-based board here, which presumably performs some machine vision tasks or similar.

Continuing the ‘bought off AliExpress’ vibe, the power supply board (pictured above) is quite literally just that. A relay board follows the same pattern, with apparently the entire contents of the camera consisting of off-the-shelf development boards and modules that are readily found for sale online.

For the camera there is a thermal camera presumably for night operations, as most of these drone swarms are launched towards Ukraine at night. Looking at the gimbal assembly it similarly feels like it was sourced off AliExpress, featuring mostly Western components, sometimes with the typical lasered-off component markings and such.

This makes one wonder how much has changed here since nearly two years ago we saw an air data computer from a similar drone that could have been sourced off AliExpress, while the Russian missile teardowns show significantly more custom hardware, presumably because those are harder to source off AliExpress.

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