Procrastineering And Simulated Annealing

November 18, 2023 by Elliot Williams 1 Comment

The software for the Supercon badge went down to the wire this year, with user-facing features being coded up as late as Thursday morning. This left “plenty of time” to flash the badges on Thursday afternoon, but they were admittedly still warm as the first attendees filed in on Friday morning. While I’ve always noted that the last minute is the best minute, this was a little close, and frankly there was an uncaught bug that we would have noticed if we had a few more hours to just play with it before showtime.

But we were by no means slacking. On the contrary, a few of us were putting in nights and full weekend days for six or eight weeks beforehand. The problem was hard, and the path to a solution was never clear, and changed depending on the immovability of the roadblocks hit along the way. This is, honestly, a pretty normal hacker development pattern.

What was interesting to me was how similar the process was to simulated annealing. This is an optimization method where you explore more of the solution space in the beginning, when the metaphorical “temperature” is hot. Later, as you’re getting closer to a good solution, you want to refine in smaller and smaller steps – it cools down. This rate of “cooling” is a tremendously important parameter in practice.

And this is exactly the way the badge development felt. We were searching in a very big solution space in the beginning, and many aspects of the firmware infrastructure were in flux. As it got closer and closer to a working solution, more and more of the code settled down, and the changes got smaller. In retrospect, this happened naturally, and you can’t always control or plan for the eureka moments, but I wonder if it’s worth thinking of a project this way. Instead of milestones, temperatures? Instead of a deadline, a freeze date.

Why Gas Turbines Rule The World

November 18, 2023 by Al Williams 27 Comments

It is an interesting fact that the most efficient way to generate electricity — at least so far — is to spin the shaft of a generator. The only real question is how you spin it. Falling water works. Heat from a nuclear reaction is another choice. For many decades, the king of the hill was steam. Now, however, gas turbines rule the electric generator landscape, and [Construction Physics] explains why in a recent post.

With a steam turbine, something burns or otherwise generates heat that boils water. The steam spins the blades, which turns the generator. With a gas turbine, the system compresses air and mixes it with gas. The hot gasses then drive the turbine, which is more efficient than using the combustion to produce steam.

Turns out, the idea for the gas turbine is very old, but material science had to catch up to be practical. Inefficient compressors led to low operating pressures, which was good, in a way, because the materials couldn’t stand the heat and pressure. However, low pressures led to inefficient turbines that were not practical.

The post is long and covers a lot of details about Carnot, Brayton, and Rankine cycles. It is a fascinating read, and we learned a few new things. Bet you will, too.

Turbines are a little like jet engines, but they transfer more power to the turbine blade instead of generating thrust. Turbines show up in odd places today. Some odder than others.

Behold The Track-Twisting Möbius Tank

November 18, 2023 by Donald Papp 17 Comments

It started with someone asking [James Bruton] about using a Möbius strip as a tank tread. He wasn’t sure what the point would be, but he was willing to make one and see what happened. Turns out it works reasonably well!

The grey plates are responsible for tensioning the tracks. Designing them as separate pieces means rework for fine-tuning avoids having to re-print structural parts.

The main design challenge was creating a tread system that would allow for the required rotation. [James] designed in the ability for each link to rotate about 18 degrees, and ensured plenty of open space on the upper side of the drive train to accommodate a full 180 degree twist. It took a little fine-tuning and looks a bit trippy, but in the end works about as well as a regular tread system.

[James] shows off a good technique to keep in mind when constructing big assemblies like this tank. It takes a lot of time and material to print large pieces, and in such cases it’s especially important to minimize rework. [James] therefore designs smaller, separate pieces as interfaces to other parts. This way, if changes are needed down the line (for example, to adjust motor placement or change tension on parts), only a smaller interface piece needs to be redone instead of having to re-print a huge part.

The unit uses an Arduino Mega, two 24 V gearmotors to drive each tread independently, an RC radio receiver, and some beefy BTS7960 DC motor drivers to drive the motors.

[James]’ unit is pretty big, but we’ve also seen 3D printed tanks capable of carrying a human driver. It’s clear that build plate size doesn’t seem to limit tank designs. Watch the Möbius tank get built and drive around in the video, just below the page break.

Continue reading “Behold The Track-Twisting Möbius Tank” →

Electric Truck Carries 74 Tons

November 17, 2023 by Al Williams 73 Comments

Thanks to the various measurement systems in use, we aren’t sure if Volvo has created an electric truck that carries 74 metric tons, 74 short tons, or 74 long tons, but either way, that’s a lot of cargo for an electric truck. After all, that’s somewhere between 148,000 and 163,000 pounds (or 67,000 kg to 74,000 kg). That’s about three times what a typical 18-wheeler with a flatbed carries in the US. In fact, on a U.S. road, trucks typically have to weigh less than 80,000 pounds, including the truck to be legal.

Well, the monster electric Volvo has two trailers, so it is more fair to compare it to turnpike doubles, which typically carry about 148,000 pounds of cargo. The truck operates 12 hours a day and charges when the driver takes a break. At the depot, charging is from two 180 kW chargers that use green electricity, according to the company. The truck has been running for a few months, although we haven’t heard more about how successful or unsuccessful it might be.

Continue reading “Electric Truck Carries 74 Tons” →

Additive Manufacturing Of Nickel Nanopillars Using Two-Photon Lithography

November 17, 2023 by Maya Posch No comments

The multistep, two-photon-lithography-based additive manufacturing method forms intermediate products of blank polymer, Ni-infused polymer, and NiO while fabricating Ni
nanopillars. (Credit: Zhang et al., 2023)

Manufacturing nano-sized features is rapidly becoming an essential part of new technologies and process, ranging from catalysts to photonics and nano-scale robotics. Creating these features at scale and in a reproducible manner is a challenge, with previous attempts using methods ranging from dealloying and focused ion beams to templated electrodeposition all coming with their own drawbacks. Here recent research by Whenxin Zhang and colleagues as published in Nano Letters demonstrates a method using additive manufacturing.

Specifically, nanopillars were printed in a hydrogel polymer with a laser-based lithography method called two-photon absorption which allows for a femtosecond laser to very precisely affect a small region within the targeted material with little impact on the surrounding area. This now solid and structured polymer hydrogel was then submerged into a Ni(NO₃)₂ solution to infuse it with nickel. After drying, the resulting structure had the polymer burned away in a furnace, leaving just the porous Ni nanopillars.

Subsequent testing showed that these nanopillars were more robust than similar structures created using other methods, presumably due to the less ordered internal physical structure of each pillar. Based on these results, it’s likely that the same approach could be used for other types of nano-sized structures.

A Low Voltage Tube Makes For A Handy Preamplifier

November 17, 2023 by Jenny List 29 Comments

When most people think of tube circuits, the first thing that comes to mind is often the use of high-voltage power supplies. It wasn’t a given for tube circuits, though, as a range of low-voltage devices were developed for applications such as car radios. It’s one of these, an ECH83 triode-heptode, which [mircemk] has taken as the basis of an audio preamplifier circuit.

The preamp circuit is pretty simple, being a two-stage single-ended design using both halves of the tube. Between the two is a three-band tone control circuit as used in classic guitar amplifiers, making for a serviceable and easily achievable way to chase that elusive “valve sound.”

There is much discussion among audio enthusiasts about the supposed benefits of vacuum technology as opposed to transistors in an amplifier. Much of it centres around the idea that tubes distort in the even harmonics while semiconductors are supposed to do so in the odd harmonics. Still, we’d be inclined to spot a bit of snake oil instead and point to early transistor amplifiers simply being not very good compared to the tube amps of the day. That said, a well-made tube amplifier set-up will sound just as amazing as it always did, and since this one is paired with a matching power amp we wouldn’t say no to it ourselves.

If you fancy messing about with tubes for not a lot, there’s a cheap module for that.

The masks with which the Intel 4004 was fabricated

Supersize Your Intel 4004 By Over 10 Times

November 17, 2023 by Julian Scheffers 22 Comments

A PCB covered in discrete transistors with light shining through it — This is quite a bit bigger than the original 12mm² die.

The Intel 4004 was among the first microprocessors and one of the first to use the MOS silicon-gate technology. In the decades long race to build bigger CPUs, it’s been mostly forgotten. Forgotten that is, until [Klaus Scheffler] supersized it over ten-fold!

The project took about 2 years to complete and re-creates it faithfully – all 2,300 transistors included – enough to run software written for the Intel 4004. But the idea for this project isn’t unique and dates all the way back to 2000, so what gives? Turning a bunch of masks for silicon fabrication into a schematic is actually harder than it seems! [Tim McNerney] originally came up with the idea to make a giant 4004 for its “35th anniversary”. [Tim] managed to convince Intel to give him schematics and other drawings and would in return make an exhibit for Intel’s museum. With the schematic straight from [Federico Faggin], software analysis tools from [Lajos Kintli] and [Klaus Scheffler] to actually build the thing, they did what [Federico] did in one year without CAD, but in two with modern tools.

The full story by [Tim] is a lot longer and it’s definitely worth a read.