Just How Vulnerable To Accidental Erasure Are EPROMs Anyway?

June 29, 2021 by 45 Comments

On the scale of things worth worrying about, having to consider whether your EPROMs will be accidentally erased by some stray light in the shop is probably pretty low on the list. Still, losing irreplaceable data can make for a bad day, so it might just pay to know what your risks really are.

To address this question, [Adrian] set out to test just how susceptible to accidental erasure some common EPROM chips are. An EPROM, or “erasable programmable read-only memory”, is a non-volatile memory chip that can be programmed electrically and then erased optically, by exposing the die inside the chip to light at a specific wavelength, usually in a special chip erasing tool. But erasure can also happen in daylight (even if it takes a few weeks), so [Adrian] cooked up an experiment to see what the risk really is.

He exposed a selection of EPROMs with known contents to UV and checked their contents. Three of the chips had a simple paper or foil label applied, while one had its quartz window exposed to the UV. As expected, the unprotected chip was erased in just 30 minutes. The covered chips, though, all survived that onslaught, and much more — up to 780 minutes of continuous exposure.

So rest easy — it seems that even a simple paper label is enough to protect your precious retro EPROMs. It’s a good data point, and hats off to [Adrian] for taking a look at this. But now we can’t help but wonder: what would a little sunscreen applied to the quartz window do to erasability? Sounds like a fun experiment, too.

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Kathleen Lonsdale Saw Through The Structure Of Benzene

June 29, 2021 by 14 Comments

The unspoken promise of new technologies is that they will advance and enhance our picture of the world — that goes double for the ones that are specifically designed to let us look closer at the physical world than we’ve ever been able to before. One such advancement was the invention of X-ray crystallography that let scientists peer into the spatial arrangements of atoms within a molecule. Kathleen Lonsdale got in on the ground floor of X-ray crystallography soon after its discovery in the early 20th century, and used it to prove conclusively that the benzene molecule is a flat hexagon of six carbon atoms, ending a decades-long scientific dispute once and for all.

Benzene is an organic chemical compound in the form of a colorless, flammable liquid. It has many uses as an additive in gasoline, and it is used to make plastics and synthetic rubber. It’s also a good solvent. Although the formula for benzene had been known for a long time, the dimensions and atomic structure remained a mystery for more than sixty years.

Kathleen Lonsdale was a crystallography pioneer and developed several techniques to study crystal structures using X-rays. She was brilliant, but she was also humble, hard-working, and adaptable, particularly as she managed three young children and a budding chemistry career. At the outbreak of World War II, she spent a month in jail for reasons related to her staunch pacifism, and later worked toward prison reform, visiting women’s prisons habitually.

After the war, Kathleen traveled the world to support movements that promote peace and was often asked to speak on science, religion, and the role of women in science. She received many honors in her lifetime, and became a Dame of the British Empire in 1956. Before all of that, she honored organic chemistry with her contributions.

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PetBot: Turn PET Bottles Into Filament

June 29, 2021 by 44 Comments

Recycling plastic into filament normally involves chopping it into tiny pieces and pushing it through a screw extruder. [JRT3D] is taking a different approach with PetBot, which cuts PET bottles into tape and then turns it into filament. See the videos after the break.

Cutting the tape and extrusion happens in two completely separated processes on the same machine. A PET bottle is prepared by cutting off the bottom, and the open rim is pushed between a pair of bearings, where a cutter slices the bottle into one long strip, as a driven spool rolls it up. The spool of tape is then moved to the second stage of the machine, which pulls the tape through a hot end very similar to that on a 3D printer. While most conventional extruders push the plastic through a nozzle with a screw, the PetBot only heats up the tape to slightly above its glass transition temperature, which allows the driven spool to slowly pull it through the nozzle without breaking. A fan cools the filament just before it goes onto the spool. The same stepper motor is used for both stages of the process.

We like the simplicity of this machine compared to a conventional screw extruder, but it’s not without trade-offs. Firstly is the limitation of the filament length by the material in a single bottle. Getting longer lengths would involve fusing the tape after cutting, or the filament after extrusion, which is not as simple as it might seem. The process would likely be limited to large soda bottle with smooth exterior surfaces to allow the thickness and width of the tape to be as consistent as possible. We are curious to see the consistency of the filaments shape and diameter, and how sensitive it is to variations in the thickness and width of the tape. That being said, as long as you understand the limitations of the machine, we do not doubt that it can be useful. Continue reading “PetBot: Turn PET Bottles Into Filament” →

The Great Windows 11 Computer Extinction Experiment

June 29, 2021 by 294 Comments

There was a time when a new version of Windows was a really big deal, such the launch of Windows 95 for which the tones of the Rolling Stones’ Start me up could be heard across all manner of media outlets. Gradually over years this excitement has petered out, finally leaving us with Windows 10 that would, we were told, be the last ever version of the popular operating system and thence only receive continuous updates

But here we are in 2021, and a new Windows has been announced. Windows 11 will be the next latest and greatest from Redmond, but along with all the hoopla there has been an undercurrent of concern. Every new OS comes with a list of hardware requirements, but those for Windows 11 seem to go beyond the usual in their quest to cull older hardware. Aside from requiring Secure Boot and a Trusted Platform Module that’s caused a run on the devices, they’ve struck a load of surprisingly recent processors including those in some of their current Surface mobile PCs off their supported list, and it’s reported that they will even require laptops to have front-facing webcams if they wish to run Windows 11.

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Garage Semiconductor Fab Gets Reactive-Ion Etching Upgrade

June 29, 2021 by 21 Comments

It’s a problem that few of us will likely ever face: once you’ve built your first homemade integrated circuit, what do you do next? If you’re [Sam Zeloof], the answer is clear: build better integrated circuits.

At least that’s [Sam]’s plan, which his new reactive-ion etching setup aims to make possible. While his Z1 dual differential amplifier chip was a huge success, the photolithography process he used to create the chip had its limitations. The chemical etching process he used is a bit fussy, and prone to undercutting of the mask if the etchant seeps underneath it. As its name implies, RIE uses a plasma of highly reactive ions to do the etching instead, resulting in finer details and opening the door to using more advanced materials.

[Sam]’s RIE rig looks like a plumber’s stainless steel nightmare, in the middle of which sits a vacuum chamber for the wafer to be etched. After evacuating the air, a small amount of fluorinated gas — either carbon tetrafluoride or the always entertaining sulfur hexafluoride — is added to the chamber. A high-voltage feedthrough provides the RF energy needed to create a plasma, which knocks fluorine ions out of the process gas. The negatively charged and extremely reactive fluorine ions are attracted to the wafer, where they attack and etch away the surfaces that aren’t protected by a photoresist layer.

It all sounds simple enough, but the video below reveals the complexity. There are a lot of details, like correctly measuring vacuum, avoiding electrocution, keeping the vacuum pump oil from exploding, and dealing with toxic waste products. Hats off to [Sam’s dad] for pitching in to safely pipe the exhaust gases through the garage door. This ties with [Huygens Optics]’s latest endeavor for the “coolest things to do with fluorine” award.

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Just How Did 1500 Bytes Become The MTU Of The Internet?

June 29, 2021 by 59 Comments

[Benjojo] got interested in where the magic number of 1,500 bytes came from, and shared some background on just how and why it seems to have come to be. In a nutshell, the maximum transmission unit (MTU) limits the maximum amount of data that can be transmitted in a single network-layer transaction, but 1,500 is kind of a strange number in binary. For the average Internet user, this under the hood stuff doesn’t really affect one’s ability to send data, but it has an impact from a network management point of view. Just where did this number come from, and why does it matter?

[Benjojo] looks at a year’s worth of data from a major Internet traffic exchange and shows, with the help of several graphs, that being stuck with a 1,500 byte MTU upper limit has real impact on modern network efficiency and bandwidth usage, because bandwidth spent on packet headers adds up rapidly when roughly 20% of all packets are topping out the 1,500 byte limit. Naturally, solutions exist to improve this situation, but elegant and effective solutions to the Internet’s legacy problems tend to require instant buy-in and cooperation from everyone at once, meaning they end up going in the general direction of nowhere.

So where did 1,500 bytes come from? It appears that it is a legacy value originally derived from a combination of hardware limits and a need to choose a value that would play well on shared network segments, without causing too much transmission latency when busy and not bringing too much header overhead. But the picture is not entirely complete, and [Benjojo] asks that if you have any additional knowledge or insight about the 1,500 bytes decision, please share it because manuals, mailing list archives, and other context from that time is either disappearing fast or already entirely gone.

Knowledge fading from record and memory is absolutely a thing that happens, but occasionally things get saved instead of vanishing into the shadows. That’s how we got IGNITION! An Informal History of Liquid Rocket Propellants, which contains knowledge and history that would otherwise have simply disappeared.

Tiny Operating System For Tiny Computer

June 28, 2021 by 12 Comments

Before the World Wide Web became ubiquitous as the de facto way to access electronic information, there were many other ways of retrieving information online. One of the most successful of these was Minitel, a French videotex service that lasted from 1980 all the way until 2012. But just because the service has been deactivated doesn’t mean its hardware can’t be used for modern builds like this Arduino-based operating system. (Google Translate from French)

Called ZARDOS, the operating system is built to run on an Arduino MEGA although a smaller version is available for the Uno. The Arduino is connected by a serial cable to the Minitel terminal. It can take input from a keyboard and PS/2 mouse and displays video on the terminal screen with the same cable. There is functionality built-in for accessing data on a cartridge system based on SD cards which greatly expands the limited capabilities of the Atmel chip as well, and there is also support for a speaker and a Videotex printer.

Even though the build uses a modern microcontroller, it gives us flashbacks to pre-WWW days with its retro terminal. All of the code is available on the project site for anyone looking to build an Arduino-based operating system, although it will take a little bit of hardware hacking to build a Minitel terminal like this. Either way, it’s a great way to revive some antique French hardware similar to a build we’ve seen which converts one into a Linux terminal.

Thanks to [troisieme_type] for the tip!