Kritik sah

We all love a good bit of bounce now and then, with everything from trampolines to bouncy castles and bouncy balls forming the staple of a wholesome childhood for many. That said, most of our bouncy experiences in day to day life concern bouncy objects that meet immovable or rigid objects, including said child having a blast in a bouncy castle. Where the physics get arguably more interesting and less intuitive is when you combine two objects that are both bouncy, with [Steve Mould] recently taking a look at the tuning of said bounciness to even kill the bounce completely. Understanding how to achieve this tuning means understanding how the kinetic energy is stored in each flexible material, and how to dissipate it in a way that doesn’t result in the aforementioned bounciness. In the simple physical demonstration setup the addition or removal of weights to the lower sprung platform tunes the response to the bouncy ball that is dropped on top of it. After going through the scienc...

Laser diodes are convenient light sources, but for precise optical work their often-elliptical beam profile leaves something to be desired. One way to get around this is to couple the beam into a single-mode optical fiber, which then emits a circular Gaussian beam from the other end. For more advanced experiments, therefore, [Diffraction Limited] built this fiber-coupled laser source . The simplest approach is to place the fiber directly against a light source, but this results in most of the light missing the three-micron fiber core. Optical fibers have an acceptance cone, and only light approaching from within this cone is coupled into the fiber. The design therefore uses an aspheric lens to focus light from the laser diode down to a tiny point matching the diameter of the fiber core, creating a cone of incoming light narrower than the acceptance cone. The body of the laser source was CNC machined out of brass, with the laser-diode press-fit in one end. The lens stands in front of...

The phenomenon of cable-shaped indents in the plastic cases of retro systems is one that’s probably painfully familiar to many a collector of such systems. Although in these situations neither side got hot enough to cause any melting – especially while disconnected in storage – it still has that same melted appearance. The real cause here is not heat, but plasticizer migration, as detailed in a recent video by [Run Stop Restored] over on YouTube. Plasticizers are an additive to many plastics that aim to make it more flexible (‘plastic’), as well as improve other characteristics of the base material, with PVC in particular relying on plasticizers to give it its desired properties for applications where PVC has to be flexible. Here the flexible cable insulation of these devices generally uses PVC, which over time can migrate to other polymers when brought into close contact for extended periods of time. The – usually ABS – enclosures of e.g. C...

Every experienced machinist knows the value of taking regular measurements. If one works carefully and checks dimensions frequently, it’s possible to make a part much more precise than could be made by relying on the machine’s accuracy alone. In a similar vein, it’s possible to make a measuring device out of comparatively crude parts, as long as their behavior is well understood. Related to both principles is [BubsBuilds]’s displacement sensor , which uses a 3D printed frame but reaches precision better than two micrometers. Admittedly the printed parts aren’t the source of the sensor’s precision, that comes from an opto-interrupter. This design has a central stylus, one end of which contacts the object under measurement. The other end flattens to a knife-edge blade, which fits between the diodes of the opto-interrupter. As the stylus point is pressed in, the blade blocks off more light from reaching the photodiode, creating an output signal proportional to displacement. To keep the ...

In the world of scientific publishing there are many reasons why a paper can be retracted, but generally there is an obvious and clearly communicated reason for doing so. Thus when [Yves Gingras] – a historian of physics – and [Mahdi Khelfaoui] – a colleague – noticed recently that two 1940s papers by [Max Planck] had been quite recently retracted, this resulted in an eyebrow-raising double-take, before naturally publishing their investigation’s findings on arXiv. They first became aware of this courtesy of the site Retraction Watch and their list of ‘ Retractions by Nobel Prize winners ‘, which had the authors do a spit-take when they saw [Max Planck] listed. This page led them to a total of two database entries , as listed above. One is for a 1940 paper, the other for a 1942 paper, only five years before [Planck]’s death. As for the provided reasons, both articles were struck with a generic ‘copyright violation’, which a...

For as popular as the piano is in music studios, homes, and schools, it almost defies logic. Compared to a guitar, harmonica, or drum set, pianos are incredibly complex machines that can have somewhere on the order of 8,000 moving parts in a case that can easily weigh hundreds of pounds and which often responds quite poorly to seasonal changes in temperature and humidity. But for putting up with all of these downsides, musicians are rewarded with an instrument that uniquely responds to touch, style, and emotion. A big reason for that is that mechanical complexity, and [Super Valid Designs] is attempting to bring that design to a drum set . Compared to the complex machinery that connects the movement of a piano’s key to its hammer striking a string, a kick drum pedal is much simpler. It can only bounce off of the drum or get “buried” where the beater remains pressed up against the drum after hitting it. [Super Valid Designs] wanted something with a bit more finesse and...

Perhaps the hardest thing for amateur astronomers just starting out is finding the things you want to look at. Prolific maker [mircemk] has submitted a quick-and-easy star-hopper device that will help guide your binoculars with laser-like precision using things you likely already have on hand: a smartphone, a mounting plate, and a green laser pointer. The smartphone is running AstroHopper, an astronomy app that uses GPS and inertial navigation to know exactly where your phone is pointing, and offer an image of the sky on the screen. There are many others of this ilk, and there’s no reason [mircemk]’s trick won’t work with your favorite. The trick is decidedly simple: the smartphone is mounted to a flat plate, in line with a green laser pointer. Careful placement aligns the axis of the phone and the laser, and the mounting plate is set up to fit a tripod. Using it is simple: with a labelled view of the sky displayed on the screen, one lines up the phone/laser combo ...

If you were in the market for a games console in 1990, the chances are that the object of your desire was either a Super Nintendo with its 16-bit 6502 derivative, or the Sega Megadrive, sold as the Genesis in North America, with its Motorola 68000. Both machines featured impressive graphics and sound for their time, but they remain firmly in the 16-bit era. Which makes it a surprise to see LinuxMD. It’s Linux, for the Sega Megadrive , with the latest mainline kernel. The Motorola 68000 series of chips was the first porting target for Linux, and is still maintained in 2026. This build runs from an SD card  in a modern Megadrive storage peripheral, and is reported to run on the original hardware. The lowly 68000 in the Sega doesn’t have a memory management unit required for the full Linux experience, so what’s really running here is a kernel compiled with the -nommu option. That in itself is a feat, on this architecture. On it you get smolutils, a cut down coreutils, an...

Offloading acceleration and braking to an electric motor in a hybrid configuration allows the less efficient combustion engine run in a more narrow set of RPM and torque ranges. In some cases the motor is decoupled from the mechanical drivetrain entirely and used simply as a generator, where it can run at a single speed all the time. And this concept isn’t limited to passenger vehicles, either. [rctestflight] put this premise to the test using a small knockoff Honda motor as a generator for an electric boat . This project builds on a previous version where he used a much smaller hobby motor to see if it could generate usable power, and that system powered a small autonomous boat as a proof-of-concept. Those motors aren’t really designed to be used in this sort of application though, so this build upgrades the internal combustion engine and pairs it with an electric skateboard motor that’s configured to run as a generator. The setup is capable of producing almost 800 ...

Sometimes, it’s hard to stop picking up your phone every few minutes to check on notifications and scroll endlessly through the slop of the day. [PushpendraC2] has been working on a solution to this problem that would ideally discourage such behavior —  a nifty little smartphone stand! The concept is straightforward enough—the smartphone stand uses a simple tactile button to determine if your smartphone is sitting on the little 3D printed shelf, or not. However, the smarts inside do a bit more than that, too. An ESP32-S3 is charged with monitoring whether the smartphone is sitting in place, and starts counting “focus time” while it’s there. If the phone is picked up, the OLED display on the shelf starts ticking down a 5-second timer to encourage you to put it back. If you don’t, the focus time is reset and you lose your streak. It’s also possible to tap a touch sensor on the device which sets a reminder timer, prompting you to put your phone b...

Reachy Mini is a limbless desktop robot from Hugging Face made for human interaction experiments, and to give you an idea of what it’s like is a guide on how to implement expressive, local conversational AI complete with head movements and antenna wiggles. It’s conversational in the sense that it aims to feel natural, with low-latency responses and the ability to interrupt, with everything running on local hardware if one so wishes. Reachy Mini can use remote services, or work in tandem with a desktop machine or laptop. The software stack is essentially VAD (voice activity detection) → STT (speech-to-text) → LLM (large language model) → TTS (text-to-speech) which allows users to tweak things to their liking, or independently swap or modify pieces as things evolve. This also allows users to tailor the services to match whatever their hardware is capable of. For example, one could easily use a frontier AI model via remote API for the LLM while keeping everything else local...

RC planes are a lot of fun, and the bigger the better! [Ramy RC] has built the world’s biggest RC A380 . At 29 ft (8.83 m) long, with a 32 foot (9.75 m) wingspan , and weighing 800 lb (362 kg), this 1/8 scale jumbo jet is not your typical model. The fuselage is built from CNC cut EPS foam layed up with fiberglass on the outside and carbon fiber inside. The wings have a combination of carbon, aluminum, foam, and wood components to handle the aerodynamic loads. The attention to detail is wild. Instead of painting the windows, each one is an actual hole in the plane with a 3D printed window frame and acrylic window. You can actually see one falling out of the plane in the video below. An Airbus mechanic in the comments even notes the landing gear door order of operations are identical to the real thing. If [Ramy] looks familiar, perhaps you remember his previous A380 build ? Much like the 747, the full size A380 is no longer in production , but they can run on cooking oil while ...

YouTube streaming typically involves a camera with an HDMI output, a USB3 HDMI digitiser, and a suitably beefy PC to run it all. It’s quite a process, and for [Coreymillia], more complex than it needs to be. He’s come up with something simpler, a dedicated self-contained streaming rig using a Raspberry Pi 4 . As you might expect it uses the Raspberry Pi HQ camera at the optical end, but it’s the software surrounding it that transforms it from a mere camera into a streaming rig. There’s a web based user interface, but perhaps more interesting are the companion dashboard peripherals. A Raspberry Pi or an ESP32 Cheap Yellow Display can both serve as a small in-view dashboard and controller. We know from experience that a stream can be a difficult thing to get right even with high-end hardware, and we’re interested to see this standalone device allowing , we hope, an easier way to do it. If you’re a streamer we’re guessing you’ll be taking a...

Swift is a relatively modern program language, appearing in 2014 as a replacement for Objective-C. Since then, it’s become a popular solution for programming apps across Apple platforms. That led [Yeo Kheng Meng] to a simple yet fun idea— porting Swift to the oldest Apple platform of all. Yes, [Yeo] managed to build a development environment for Swift that targets the Apple II platform. Not just one machine, either—everything from the original Apple II up to the IIe and a little beyond. Now, the Apple II is very different from modern Macs and iPhones and the like, having debuted in 1977 with a 1 MHz 6502 CPU and a minuscule 4 KB of RAM. But that doesn’t mean you can’t use a modern language to develop for it! [Yeo] does a great job of explaining how it all works, and how Claude Code and GPT 5.5 Codex were used to help piece things together. The compiler is set up to spit out bytecode that’s executed by a virtual machine running on the 6502. The target was to all...

The recently released Valve Steam Machine is that it uses a custom, non-standard PCB and non-standard power supply. This fact apparently has irked some people who decided that it makes perfect sense to try and cram a Mini-ITX board, Small Form Factor (SFF) PSU and full-sized discrete GPU into an enclosure of the same size. Cue the SFF Mini-ITX Steam Machine Case project by [3DCatt] over at Printables. This is apparently a project done in cooperation with AMD’s [Jacob Terkelsen], who showed off the 3D printed case stuffed full with the aforementioned parts, which includes a GeForce RTX 5060 GPU. Of note is that the Valve Steam Machine uses a different cooling configuration as it has both the CPU and GPU on the same PCB. These share the same massive heatsink, as can be seen in e.g. the [Gamers Nexus] teardown video . For this angular imitation machine it would have been nice to use a blower-style GPU, to exhaust the hot air rather than dump it all into the case. This is also an ...

When people start ranting about AI, you can be sure a few things are going to come up during the two-minutes hate: job loss, higher power bills, the neverending tide of low-effort slop, and wasting precious freshwater. Well, NVIDIA wants to take away that last one, beacause the all- water cooled Ruben architecture won’t need any evaporative cooling — coolant can stay in a closed loop, and never needs to be cooled below 45 C, or 113 F. This sort of coolant loop should be familiar to anyone who has ever built a water-cooled PC or PlayStation : there’s a glycol-water mix, water blocks, and a radiator to reject heat to the environment. NVIDIA doesn’t mention if their new servers come with RGB lighting, but we’d like to imagine it’s an option. The big difference — aside from the rainbow LEDs– between a Ruben server and your old gaming rig is that in these racks, everything is on a waterblock. If there’s a chip on the motherboard generat...

Recently [Bits und Bolts] found himself in a bit of a pickle, when on boot his PC would complain about a connected USB device drawing too much power, before shutting down again. After unplugging various USB devices, the problem was narrowed down to an Elgato Cam Link 4K video capture device. Some prodding and poking around with a thermal camera on the disassembled device while powered showed that an onboard IC had sprung a power leak. Sadly, even asking nicely, Elgato support wasn’t going to provide board-level repair help, so this was left as an exercise to the owner . Although the markings on the chip didn’t offer much help, it turns out that this is a more common issue, with a convenient repair guide by [Uldis Melderis] identifying the part as the TI  TLV62585 buck regulator. After purchasing a couple of spares, the defective IC could then be replaced. Following this a quick test showing decidedly less angry electrons. From there it was a matter of reassembling the d...

[Dominic Buchstaller] wanted a neat, tidy entryway keypad that actually looked good. Prime goals were something slim, wireless, and with no visible screws. Dependency on the cloud was also a no-go. With few ready-to-go options available on the market, he set about whipping up his own. The heart of the build is an ESP32-C6 microcontroller devboard. This device has the benefit of including Zigbee communication functionality baked right into the chip. It’s hooked up to an MPR121 capacitive touch controller, which allows different segments of the touchpad PCB to act as capacitive buttons for numerical entry. The number labels are directly printed on the PCB solder mask, so there’s no overlay or other label required on top. Power is courtesy of a 1300 mAh lithium-polymer cell which gives a useful lifespan of six months between recharges. A simple 3D-printed case holds everything together and completes the clean and simple look. [Dominic] notes that it’s possible to also us...

Have you ever spotted something in a catalog or on a website and just known you had to build a project around that one part? That’s how [nilseuropa] felt about the Waveshare ESP32-S3-RLCD-4.2, which — as you might guess from the name — pairs an ESP32-S3 with a reflective LCD. With a screen reminiscent of a palmtop of yore, [nilseuropa] wanted a personal device, and needed something to run on it. That’s where Solar OS comes in. Physically he’s paired the Waveshare board with a mini keyboard and put them together in a handsome 3D printed case with a battery. The slabtop form-factor was more for ease-of-creation than any preference; in the project’s reddit thread [nils] is reaching out for help making something cooler, possibly of the palmtop form-factor. He also describes some of the thinking behind his operating system. You had us at “terminal”. H’s not starting entirely from scratch: it’s based on FreeRTOS and the ESP-IDE ...

The smart TV is a fixture in most houses, variously an entertainment portal, corporate data gathering tool, or sometimes an outright spy. It’s a nice monitor with a computer built in, so can that computer be released to do something else? It’s a question [Xen’on] is answering, on an Android-based TV . The guide is not too different from many others relating to Android phones, with a few quirks. An Android Debug Bridge (ADB) connection is established, root access is gained using Shizuku , and then it’s a case of installing a more conventional Linux front end with the Openbox window manager through Termux . There are some TV-specific things to do with handling power cycles, but the TV is now a usable Linux box. It’s always good to see someone retrieve the Linux underneath a locked-down device, but the system spec tells the real story. By the looks of things this TV is a few years old as it had an Android version that’s a bit long in the tooth, and thu...

In structures like photovoltaic cells there is only a limited spectrum of wavelengths that can perform useful work, with the remaining wavelengths of electromagnetic radiation effectively wasted. If the energy of such wavelengths could be coaxed into this useful spectrum, this could then correspondingly boost the performance of the devices, but doing so is not straightforward. Going from lower-energy photons to higher-energy photons is very inefficient, with a recent study by [Thilini Ishwara] et al. demonstrating a liquid triplet medium that has a conversion efficiency of about 8.2%. Generally the absorption and emission of electromagnetic radiation involves a shift to a lower energy state, the Stokes shift , but the inverse anti-Stokes shift – the goal of photon upconversion – is decidedly less common, even if it finds uses today in for example industrial pigments that can absorb in the near-infrared and re-emit in the visible spectrum. This is practical in luminescent ...

Although paperbacks are a much-loved aspect of the literary world, they are not really intended to last the decades the way that hardcover books are. Beyond the typical ravaged covers, paperbacks also tend to suffer from a warped spine, where the formally flat spine gets a definite inwards curve due to the ravages of moisture, temperature, failing glue and the passing of time in general. If this bothers you, then [Book Care Studio] shows a simple technique using which these spines can be flattened again. All that you need for this approach are two cutting boards and two clamps to provide some clamping force on the book, along with a heat gun and some patience. The book is clamped between the two boards with the spine sticking out. By putting said spine flat on e.g. a table and pushing on the opposite side while alternatingly briefly releasing the clamps, the spine can be forced into a flatter state. Without forcing this and then flipping the paperback sandwich around to heat the spi...

The 1981 Casio VL-1 was a fine cheap keyboard. It had a robust build, though an admittedly limited sound palette. [Max Vega] had one of these charming instruments, and decided to use modern tech to rebrain it for the modern world. The original electronics of the VL-1 were largely surplus to requirements for this build. The original interface and speaker were kept in service, while the rest of the monophonic sound synthesis hardware was removed. [Max Vega] enlisted an ESP32-C3 to run the show, turning the VL-1 into a ROMpler instead. If you’re unfamiliar with the term, it refers to a keyboard or other instrument that relies on hardcoded sample playback instead of raw synthesis. The ESP32 loads its samples from a microSD card, which provides an enormous amount of storage for different sound packs. Selecting different instruments is handled with a simple interface built around the original buttons and a OLED screen.  Playing the instrument is still the same using the simple keyboard...