Polystyrene Foam Can Be Gasoline With Some Help

August 4, 2026 by Maya Posch 23 Comments

Styrofoam – or closed-cell extruded polystyrene (XPS) foam if you want to be precise – is one of those materials that is both super versatile for packaging and insulation, but also a menace when it comes to disposal, even if you ignore that the monomer styrene (C₈H₈) is a known mutagenic toxin. One of the more creative ways to deal with the metric tons of polystyrene waste generated each year is to turn it into gasoline, as demonstrated by [Lowered Expectations] in a recent video.

With polystyrene being just another hydrocarbon polymer, the idea of turning these polymers into the mixture of hydrocarbon chains we call ‘gasoline’ isn’t so crazy. The problem is mostly doing it in a way that makes some economic sense and doesn’t risk turning your domicile into a hazmat risk site or threaten the health of you, your loved ones and the neighborhood.

The method demonstrated in the video uses fairly basic methods involving pyrolysis and distillation. The first step involves dissolving the polystyrene in gasoline that was previously recovered from stale gasoline, which is another dangerously fun science experiment. This creates a thick slurry that’s then put into the distillation flask for the heating phase.

After testing the distillates for spark ignition the useful distillates were combined with fuel stabilizer added. Before tossing this into a gasoline engine tank for further testing, the concerns of auto-polymerization of styrene monomers are addressed, which requires special inhibiters.

Although this mixture runs a gasoline generator just fine, a borescope inspection of the cylinders showed a build-up of a shiny, gummy residue. There’s also the issue that this mixture contains styrene monomers, which are as noted very unhealthy to breathe in from either the fuel or any remaining monomers in the exhaust. Definitely not something to try at home, basically.

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Testing Hundreds Of Used LFP Cells Requires Some Automation

August 4, 2026 by Maya Posch 7 Comments

Although Li-ion cells have become a lot cheaper over the years, if you wish to buy hundreds of high-quality ones for that performance go-kart project, you may feel financially pressured into going for the option of stripping down years-old commercial battery packs instead.

While this is a financially sound option, you do have to figure out what the condition is of each cell before you happily stuff them into a new battery pack for said go-kart, as [Within Tolerance] recently did.

This is something that can be done manually, but for the 768 lithium iron phosphate (LFP) cells that were obtained for this project that’d be quite the tedious task. Hence it was decided to instead spend that time designing a system to automate this process, capable of charging, discharging, measuring and quantifying individual cells.

You can find the resulting Cell Goblin battery tester project on GitHub, which entails a custom PCB featuring an ESP32-S2 as the brains and associated software to monitor the process on a connected PC. Fortunately the issues on the PCB that are described in the video are claimed to be fixed in the repository version.

Using five of these dual-cell cell testers it was possible to run through the hundreds of cells with ten cells at a time. An internal resistance meter was also wired into the PC-based software via its UART. As of publication of the video the testing was still in progress, which gives some idea of how long it takes to work through those cells.

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Sketching Temporary Circuits With A Light-Triggered Floquet Topological Insulator

August 3, 2026 by Maya Posch 7 Comments

In semiconductor technology, a base material like silicon is permanently modified to induce certain electrical behavior. In comparison a topological insulator material could be used to create temporary circuits using something like light exposure. An example of this is the Floquet topological state, which has long been theorized, but is now claimed to have been demonstrated in SnTe semiconductor material, per a paper by [F. Chassot] et al. in Nature Physics.

The concept of topological insulators was first proposed in 1985, but proving their existence was hard. Recently photonic Floquet topological insulators (PFTIs) have gained interest, with experiments by [Qian Ma] et al. in 2025 as well as other teams confirming aspects of the theory.

This recent publication by [Chassot] et al. would thus confirm that optical control of topological insulators is thus possible. At the core of this effect is the band inversion that results from the light pulses, with the change in conduction being very brief, essentially for as long as the femtosecond pulses were maintained.

Although still very much in the fundamental research phase, the research on these electronic topological insulators offers an interesting look at potential new technologies, much like the field of photonic topological insulators does for photonics.

Energizing A Vacuum Tube Flip-Flop Module Of The IBM 604

August 3, 2026 by Maya Posch 10 Comments

Reverse-engineered schematic of the IBM 604's TR-3 module. (Credit: Ken Shirriff) — Reverse-engineered schematic of the IBM 604’s TR-3 module. (Credit: Ken Shirriff)

Taking a break from ogling microscopic features in Intel’s semiconductor processors, [Ken Shirriff] is back to instead poking at decidedly macroscopic pluggable modules from the 1948 IBM 604 Electronic Calculator. This time around it’s one of the so-called trigger modules in the form of the TR-3, which uses a flip-flop circuit to implement the timing signals and pulses that made the 604 work.

This differs from the thyratron module that we covered previously. A thyratron is a high current switch and rectifier, which is useful more for the periphery of the computer system. These TR-3s on the other hand were used to implement the basic logic circuits, even if a flip-flop by itself seems rather boring, being just a circuit that toggles between two states.

In this TR-3 module we find a 2033 dual triode design which thus increases density by having the two inverters of the flip-flop in the same tube. The rest of the module is taken up by the requisite capacitors and resistors that complete the circuit. After wiring up this original module, [Ken] was able to make it trigger somewhat reliably, requiring a stable input trigger.

Notable is that in the IBM 650 from 1954 this flip-flop circuit was abandoned in favor of one based on diode logic, presumably to use more reliable Boolean logic instead of the much fussier analog interactions. Naturally, in the first transistorized computers the use of diode-transistor logic (DTL) was exceedingly common, so this makes a lot of sense.

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Making A Retro(ish) Game Console From Scratch

August 2, 2026 by Maya Posch 11 Comments

As easy as it is to make a late 1980s-style game console using a modern microcontroller, there’s arguably more fun in doing things the traditional way. This is the challenge that [Throaty Mumbo] took upon himself when he embarked on his retro game console project, called simply the Game Console V2.

In the accompanying video the development process and other details are covered and demonstrated. Most notable perhaps are the proper cartridges with ROMs on a parallel bus rather than something like SD cards, and the absence of any modern ports including even VGA. This means only composite AV output like in the good old days of RF splitters and other assorted fun.

The NTSC output signal is generated by an RP2350 MCU in the form of the PGA-shaped PGA2350 breakout board that’s wired into a 6-bit R-2R network for RGB332 output via the RCA jack, while audio is fed into a PCM5102A I2S DAC. For controllers you get 4-pin Bulgin SA2367 connectors and an N64-compatible protocol.

It’s noted that the use of an RP2350B MCU is temporary, as the goal with the V3 version of the project is to take it into a proper 8- or 16-bit CPU direction. We’re certainly looking forward to seeing this next revision of what looks to be a pretty interesting game console.

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Turning Fruits Into Ethylene And Ethane Refrigerant

August 2, 2026 by Maya Posch 11 Comments

One of the best parts about DIY chemistry and physics projects is that you get to decide how early in the supply chain you want to begin, such as with [Hyperspace Pirate]’s adventures in ethanol production from sugar fermentation. Although you can certainly just buy packs of sugar and yeast from the store and pretend that this will be helpful once the world embraces its Mad Max era, you may as well start with the stuff that actually grows on trees, like fruit.

While you could use the ethanol produced this way as ethanol fuel in combustion engines and the like, you can also turn the ethanol into ethylene and ethane. That way you can fill up your refrigerator, freezer, and air conditioner to keep your perishable foods and yourself fresh as the outside world descends into highly questionable fashion choices.

Even outside such a scenario it makes sense to generate your own ethane and ethylene, due to how much these refrigerants cost. Once you have the ethanol, some aluminium oxide catalyst at 350°C is enough to produce ethylene and water. Producing ethane is admittedly a bit more involved, requiring acetobacter bacteria to produce acetic acid, along with baking soda, a platinum anode and a few more odds and ends.

Producing butene and even longer chains from ethylene is also possible as a next step, but this gets even hairier than producing ethane from ethanol, so we’re likely to see this in a future update after all the low-hanging fruit has been harvested.

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The Seven Sensors And Breakout Boards To Avoid In A Product

August 2, 2026 by Maya Posch 57 Comments

We’ve all seen these sensors and modules kicking around, as part of beginner kits, strapped into prototypes and potentially even in products deployed in the field. Yet as [John Teel] rightfully points out in a recent video, most of these have no business ever being used in a real product, and might not even be suitable for prototyping.

First up is a combination of the related DHT11 and DHT22 temperature-humidity sensors. As common as these are, they’re also pretty sketchy with their proprietary one-wire protocol and at most questionable accuracy, worsened by not having a good supply chain. The replacements are plentiful: the SHT40 and SHT41, the Bosch Sensortec BME280 or BMP180, as well as TI’s HDC3020. These get you standard I2C communication and a supply chain plus a datasheet you can trust.

Second is the HC-SR04 ultrasonic distance sensor. Although fine for prototyping, it’s a 5 V module, lacks temperature compensation and other features that’d be needed outside a temperature-controlled room. Here ST’s VL53 Time-of-Flight sensors are a good alternative, containing a range of sensors of which we covered the fancier VL53L5CX previously for 3D scanning a room. Of course, you can also use reflective IR as a good cheap alternative.

Third is the HC-SR501 passive infrared (PIR) motion module. This one is also fine for PIR and motion sensing prototyping, but is too inconsistent and power-hungry for production. Instead you can get much better and much smaller PIR modules, like the Panasonic EKMC and EKMB, or the ST STHS34 IR motion and presence sensor.

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