Several people at a museum exhibit about magnetism

Hands-On Museum Exhibit Brings Electromagnetism To Life

January 17, 2023 by 5 Comments

Magnets, how do they work? Although the quantum mechanics behind ferromagnetism are by no means easy, a few simple experiments can give you a good grasp of how magnets attract and repel each other, and show how they interact with electric phenomena. [Niklas Roy] built an exhibit for the Technorama science museum in Switzerland that packs a bunch of such electromagnetic experiments in a single package, appropriately called the Visitors Magnet.

The exhibit consists of a big magnet-shaped enclosure that contains a variety of demonstrators that are all powered by magnets. They range from simple compasses to clever magnetic devices we find in the world around us: flip-dot displays for instance, on which you can toggle the pixels by passing a magnet over them. You can even visualize magnetic field lines by using magnetic viewing film, or turn varying fields into audio through a modified telephone receiver.

Another classic demonstrator of electromagnetism is a color CRT monitor, which here displays a video feed coming from a camera hanging directly overhead. Passing a magnet along the screen makes all kind of hypnotizing patterns and colors, amplified even more by the video feedback loop. [Niklas] also modified the picture tube with an additional coil, connected to a hand-cranked generator: this allows visitors to rotate the image on the screen by generating an AC current, neatly demonstrating the interaction between electricity and magnetism.

The Visitors Magnet is a treasure trove of big and small experiments, which might not all withstand years of use by museum guests. But that’s fine — [Niklas] designed the exhibit to be easy to maintain and repair, and expects the museum to replace worn-out experiments now and then to keep the experience fresh. He knows a thing or two about designing engaging museum exhibits, with a portfolio that includes vector image generators, graffiti robots and a huge mechanical contraption that plays musical instruments.

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All About USB-C: High-Speed Interfaces

January 17, 2023 by 40 Comments

One amazing thing about USB-C is its high-speed capabilities. The pinout gives you four high-speed differential pairs and a few more lower-speed pairs, which let you pump giant amounts of data through a connector smaller than a cent coin. Not all devices take advantage of this capability, and they’re not required to – USB-C is designed to be accessible for every portable device under the sun. When you have a device with high-speed needs exposed through USB-C, however, it’s glorious just how much USB-C can give you, and how well it can work.

The ability to get a high-speed interface out of USB-C is called an Alternate Mode, “altmode” for short. The three altmodes you can encounter nowadays are USB3, DisplayPort and Thunderbolt, there’s a few that have faded into obscurity like HDMI and VirtualLink, and some are up and coming like USB4. Most altmodes require digital USB-C communication, using a certain kind of messages over the PD channel. That said, not all of them do – the USB3 is the simplest one. Let’s go through what makes an altmode tick. Continue reading “All About USB-C: High-Speed Interfaces” →

The First Afghan Sports Car Has An Engine You Shouldn’t Mock

January 17, 2023 by 125 Comments

In the news today, Afghanistan has made its first sports car, and it’s a sleek and low-slung model with a throaty exhaust note that would get a second look on the Autobahn just as much as it does on the streets of Kabul. Making a modern sports car is an impressive achievement no matter where you do it, but it wouldn’t be something we’d share with you were it not for how the story is being reported. The general tone of Western reporting is focused not upon the car itself, but instead poking fun of it for using a Toyota engine also found in a Corolla.

Anyone who grew up during the Cold War will remember the rhetoric of the era with respect to technology. To paraphrase a little, our planes or rockets were based on the finest and latest high technology, we were told, while theirs were held together with string and sealing wax from the 1940s. This neglected the fairly obvious fact that Soviet probes were visiting all the planets, something they must have had some pretty good tech at their disposal to achieve. This was then explained as the product of their having stolen all our super-advanced Western tech, something we now know that our lot weren’t averse to either when the opportunity arose.

It’s this which is brought to mind by the mirth of the Western commentators at the Afghan car’s supposedly humble engine. It doesn’t matter what you think of the Afghan regime (and there’s plenty there to criticize), the car should be assessed on its merits. After all, it’s hardly as though the engine in question didn’t find its way into more than one sports car that Western commentators might find appealing.

Take A Deep Dive Into A Commodity Automotive Radar Chip

January 17, 2023 by 24 Comments

When the automobile industry really began to take off in the 1930s, radar was barely in its infancy, and there was no reason to think something that complicated would ever make its way into the typical car. Yet here we stand less than 100 years later, and radar has been perfected and streamlined so much that an entire radar set can be built on a single chip, and commodity radar modules can be sprinkled all around the average vehicle.

Looking inside these modules is always fascinating, especially when your tour guide is [Shahriar Shahramian] of The Signal Path, as it is for this deep dive into an Infineon 24-GHz automotive radar module. The interesting bit here is the BGT24LTR11 Doppler radar ASIC that Infineon uses in the module, because, well, there’s really not much else on the board. The degree of integration is astonishing here, and [Shahriar]’s walk-through of the datasheet is excellent, as always.

Things get interesting once he gets the module under the microscope and into the X-ray machine, but really interesting once the RF ASIC is uncapped, at the 15:18 mark. The die shots of the silicon germanium chip are impressively clear, and the analysis of all the main circuit blocks — voltage-controlled oscillator, power amps, mixer,  LNAs — is clear and understandable. For our money, though, the best part is the look at the VCO circuit, which appears to use a bank of fuses to tune the tank inductor and keep the radar within a tight 250-Mz bandwidth, for regulatory reasons. We’d love to know more about the process used in the factory to do that bit.

This isn’t [Shahriar]’s first foray into automotive radar, of course — he looked at a 77-GHz FMCW car radar a while back. That one was bizarrely complicated, though, so there’s something more approachable about a commodity product like this.

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A white stairwell ceiling with a rack holding clothes. The rack follows the slope of the ceiling and is attached to a series of ropes and pulleys to let it got up and down.

Stairway Drying Rack Rises Above The Rest

January 16, 2023 by 14 Comments

Finding space to dry clothes can be challenging in smaller spaces. [Tom Parker] solved this conundrum in his one bedroom apartment by putting a drying rack in his stairwell.

By making the laundry rack fold up above the stairwell, [Parker] can dry his clothes without them taking up a lot of precious floor space. A pole is used to is raise and lower a dowel rod attached to two lines of paracord running over pulleys and to the end of the rack. Each moving corner of the rack also has a set length of cord attached to prevent the rack from rotating too far down as well as providing a safety mechanism should one of the other lines of cord snap.

The rack is bolted-together, laser cut 1.5mm thick mild steel with 15 mm dowels attached to the sides via threaded inserts. Spacing is set for the raised rack to put clothes at 75 mm apart. Plywood pieces interface the rack with the wall to avoid damaging the drywall.

If you’re looking for more laundry hacks, check out this Smart Clothes Dryer or How Robots Suck at Folding Laundry.

It’s Not Easy Counting Transistors In The 8086 Processor

January 16, 2023 by 15 Comments

For any given processor it’s generally easy to find a statistic on the number of transistors used to construct it, with the famous Intel 8086 CPU generally said to contain 29,000 transistors. This is where [Ken Shirriff] ran into an issue when he sat down one day and started counting individual transistors in die shots of this processor. To his dismay, he came to a total of 19,618, meaning that 9,382 transistors are somehow unaccounted for. What is going on here?

The first point here is that the given number includes so-called ‘potential transistors’. Within a section of read-only memory (ROM), a ‘0’ would be a missing transistor, but depending on the programming of the mask ROM (e.g. for microcode as with a CISC x86 CPU), there can  be a transistor there. When adding up the potential but vacant transistor locations in ROM and PLA (programmable logic array) sections, the final count came to 29,277 potential transistors. This is much closer to the no doubt nicely rounded number of 29,000 that is generally used.

[Ken] also notes that further complications here are features such as driver transistors that are commonly found near bond wire pads. In order to increase the current that can be provided or sunk by a pad, multiple transistors can be grouped together to form a singular driver as in the above image. Meanwhile yet other transistors are used as (input protection) diodes or even resistors. All of which makes the transistor count along with the process node used useful primarily as indication for the physical size and complexity of a processor.

Impressive Sawdust Briquette Machine

January 16, 2023 by 28 Comments

When you are a life long carpenter with an amazing workshop, you’re going to make a lot of saw dust, and managing its collection and storage poses quite a challenge. [Russ] from [New Yorkshire Workshop] built an impressive Briquette press to handle the problem.

It’s a hydraulic press that ingests  saw dust and spits out compressed briquettes ready for fueling his rocket mass heater. The build starts with a batch of custom, laser cut steel parts received from Fractory. The heart of the machine is a 300 mm stroke hydraulic cylinder with a beefy 40 mm rod. The cylinder had to be taken apart so that the laser cut mounting flanges could be welded, slowly so as not to deform the cylinder. The intake feed tube was cut from a piece of 40 mm bore seamless tube. A window was cut in the feed tube and funnel parts were welded to this cutout. The feed tube assembly is then finished off with a pair of mounting flanges. The feed tube assembly is in turn welded to the main feed plate which will form the base of the saw dust container. The hydraulic cylinder assembly is mated to the feed tube assembly using a set of massive M10 high tensile class 10.9 threaded rods. The push rod is a length of 40 mm diameter mild steel bar stock, coupled to the hydraulic cylinder using a fabricated coupling clamp. On the coupling clamp, he welded another bracket on which a bolt can be screwed on. This bolt helps activate the limit switches that control the movement of the hydraulic cylinder and the feed motor. Continue reading “Impressive Sawdust Briquette Machine” →