2025 Component Abuse Challenge: The Opto Flasher

October 29, 2025 by 6 Comments

There’s a part you’ll find in almost every mains powered switch mode power supply that might at first appear to have only one application. An optocoupler sits between the low voltage and the high voltage sides, providing a safely isolated feedback. Can it be used for anything else? [b.kainka] thinks so, and has proved it by making an optocoupler powered LED flasher.

If a part can be made to act as an amplifier with a gain greater than one, then it should also be possible to make it oscillate. We’re reminded of the old joke about it being very easy to make an oscillator except when you want to make one, but in this case when an optocoupler is wired up as an inverting amplifier with appropriate feedback, it will oscillate. In this case the rather large capacitor leading to a longish period, enough to flash an LED.

We like this circuit, combining as it does an unexpected use for a part, and a circuit in which the unusual choice might just be practical. It’s part of our 2025 Component Abuse Challenge, for which you just about still have time to make an entry yourself if you have one.

2025 Hackaday Component Abuse Challenge

This Reactor Is On Fire! Literally…

October 29, 2025 by 50 Comments

If I mention nuclear reactor accidents, you’d probably think of Three Mile Island, Fukushima, or maybe Chernobyl (or, now, Chornobyl). But there have been others that, for whatever reason, aren’t as well publicized. Did you know there is an International Nuclear Event Scale? Like the Richter scale, but for nuclear events. A zero on the scale is a little oopsie. A seven is like Chernobyl or Fukushima, the only two such events at that scale so far. Three Mile Island and the event you’ll read about in this post were both level five events. That other level five event? The Windscale fire incident in October of 1957.

If you imagine this might have something to do with the Cold War, you are correct. It all started back in the 1940s. The British decided they needed a nuclear bomb project and started their version of the Manhattan Project called “Tube Alloys.” But in 1943, they decided to merge the project with the American program.

The British, rightfully so, saw themselves as co-creators of the first two atomic bombs. However, in post-World War paranoia, the United States shut down all cooperation on atomic secrets with the 1946 McMahon Act.

We Are Not Amused

The British were not amused and knew that to secure a future seat at the world table, it would need to develop its own nuclear capability, so it resurrected Tube Alloys. If you want a detour about the history of Britan’s bomb program, the BBC has a video for you that you can see below.

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A photo of the MMD-1 on the workbench.

Restoring The E&L MMD-1 Mini-Micro Designer Single-Board Computer From 1977

October 29, 2025 by 9 Comments

Over on YouTube [CuriousMarc] and [TubeTimeUS] team up for a multi-part series E&L MMD-1 Mini-Micro Designer Restoration.

The E&L MMD-1 is a microcomputer trainer and breadboard for the Intel 8080. It’s the first ever single-board computer. What’s more, they mention in the video that E&L actually invented the breadboard with the middle trench for the ICs which is so familiar to us today; their US patent 228,136 was issued in August 1973.

The MMD-1 trainer has support circuits providing control logic, clock, bus drivers, voltage regulator, memory decoder, memory, I/O decoder, keyboard encoder, three 8-bit ports, an octal keyboard, and other support interconnects. They discuss in the video the Intel 1702 which is widely accepted as the first commercially available EPROM, dating back to 1971.

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Expert Systems: The Dawn Of AI

October 29, 2025 by 18 Comments

We’ll be honest. If you had told us a few decades ago we’d teach computers to do what we want, it would work some of the time, and you wouldn’t really be able to explain or predict exactly what it was going to do, we’d have thought you were crazy. Why not just get a person? But the dream of AI goes back to the earliest days of computers or even further, if you count Samuel Butler’s letter from 1863 musing on machines evolving into life, a theme he would revisit in the 1872 book Erewhon.

Of course, early real-life AI was nothing like you wanted. Eliza seemed pretty conversational, but you could quickly confuse the program. Hexapawn learned how to play an extremely simplified version of chess, but you could just as easily teach it to lose.

But the real AI work that looked promising was the field of expert systems. Unlike our current AI friends, expert systems were highly predictable. Of course, like any computer program, they could be wrong, but if they were, you could figure out why.

Experts?

As the name implies, expert systems drew from human experts. In theory, a specialized person known as a “knowledge engineer” would work with a human expert to distill his or her knowledge down to an essential form that the computer could handle.

This could range from the simple to the fiendishly complex, and if you think it was hard to do well, you aren’t wrong. Before getting into details, an example will help you follow how it works.

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Recreating A Homebrew Game System From 1987

October 29, 2025 by 10 Comments

We often take for granted how easy it is to get information in today’s modern, Internet-connected world. Especially around electronics projects, datasheets are generally a few clicks away, as are instructions for building almost anything. Not so in the late 80s where ordering physical catalogs of chips and their datasheets was generally required.

Mastering this landscape took a different skillset and far more determination than today, which is what makes the fact that a Japanese electronics hobbyist built a complete homebrew video game system from scratch in 1987 all the more impressive.[Alex] recently discovered this project and produced a replica of it with a few modern touches.

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All Hail The OC71

October 29, 2025 by 47 Comments

Such are the breadth of functions delivered by integrated circuits, it’s now rare to see a simple small-signal transistor project on these pages. But if you delve back into the roots of solid state electronics you’ll find a host of clever ways to get the most from the most basic of active parts.\

Everyone was familiar with their part numbers and characteristics, and if you were an electronics enthusiast in Europe it’s likely there was one part above all others that made its way onto your bench. [ElectronicsNotes] takes a look at the OC71, probably the most common PNP germanium transistor on the side of the Atlantic this is being written on.

When this device was launched in 1953 the transistor itself had only been invented a few years earlier, so while its relatively modest specs look pedestrian by today’s standards they represented a leap ahead in performance at the time. He touches on the thermal runaway which could affect germanium devices, and talks about the use of black silicone filling to reduce light sensitivity.

The OC71 was old hat by the 1970s, but electronics books of the era hadn’t caught up. Thus many engineers born long after the device’s heyday retain a soft spot for it. We recently even featured a teardown of a dead one.

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The winning entry, a photo of a fly on a grain of rice.

Nikon Small World Competition Announces 2025 Winners

October 28, 2025 by 3 Comments

They say that, sometimes, less is more. That would certainly apply to photomicrography, where you want to take pictures of tiny things. Nikon agrees, and they sponsor the Small World contest every year. The 2025 winners are a big — or not so big, maybe — deal.

This photomicrography competition dates back to 1975, so this is the 51st set of winners. First place went to [Zhang You] for his photograph of a rice weevil (sitophilus oryzae) on a grain of rice.

[You] is an entomologist from the Entomological Society of China. He says, “It pays to dive deep into entomology: understanding insects’ behaviors and mastering lighting, a standout work blends artistry with scientific rigor, capturing the very essence, energy, and spirit of these creatures.” We can’t argue with the results.

If you’re interested in Nikon and photography, you might also be interested in repairing a broken lens or a Nikon D3.