Testing Cheap DC Breakers And How To Not Start Fires

October 28, 2025 by 11 Comments

One characteristic of adding PV solar to homes is a massive increase in high-voltage and high-current DC installations. With this comes a need for suitable breakers, but without the requisite knowledge it can be easy to set up a fire hazard. There is also the issue of online shopping platforms making it easy to get fuses and breakers that may not be quite as capable as they claim, never mind being rated for DC use.

Recently [Will Prowse] had a poke at a range of common purportedly DC-rated breakers from everyone’s favorite US-based seller of tat, to see whether they should be bought or avoided at all cost. Perhaps unsurprisingly the cheap breakers are about as dodgy as you’d imagine. With a hundred plus amps flowing through them they get surprisingly crispy, even if they generally did their job. Minus the few that arrived in a broken condition, of course.

Ultimately [Will] found that the molded case circuit break (MCCB) by one ‘DIHOOL’ performed the best. Compared to the competition, it is much larger and has sizeable terminals that avoid the quaint heat-soaking issues seen with the cheap-and-cheerful rest. At a mere $34 for the 125A-rated version, it’s still a fraction of the cost of a comparable Eaton MCCB, but should upset your insurance company significantly less than the alternatives.

Don’t forget to add in fuses, with [Will] testing a range of cheapo 12V DC fuses, to see which one will prevent fires, and which one cause them. Unsurprisingly, some of them like the Bojack-branded ones ran very hot, making them more of a liability than an asset.

As for what makes DC breakers so different from AC one is that the extinguishing point of a DC arc is much steeper, which means that an AC breaker is likely to fail to extinguish the arc when used for DC applications. This is why a properly rated and ideally certified breaker is essential, and also not really the point where you want to start saving money.

Continue reading “Testing Cheap DC Breakers And How To Not Start Fires” →

Original E39 Head Unit Modernized

October 28, 2025 by 24 Comments

Although most modern cars have moved to using proprietary components nearly everywhere, especially when it comes to infotainment systems, for a brief moment which peaked in the 90s and 00s most cars shipped with radios that fit in a standard size opening called a DIN slot. If you wanted a new Pioneer or Kenwood stereo it was usually a simple matter to slide the factory radio out and put your choice of aftermarket head unit in its place. [Stefan] has an E39 BMW from this era and wanted to upgrade the factory radio but use the original hardware instead of replacing it.

This isn’t just a simple stereo upgrade either. [Stefan] has gone all-out for this build which he started in 2020. Beginning with a Kotlin/Jetpack Compose Linux application to handle control input from the vehicle’s various knobs and buttons he moved on to a map application and an on-screen keyboard. From there he implemented VGA to send video to the OEM screen, and now has a fully functional system based on a Raspberry Pi. It does everything the original unit can do including playing music and showing the feed from the backup camera, plus adds plenty of new, modern features like Bluetooth.

For a certain classic car enthusiast, this build hits a sweet spot of modernizing a true classic like the E39 without removing or permanently modifying any OEM components. The amount of work that went into it is pretty staggering as well, with [Stephan] putting in over 100 hours of work just to get the video signal timing correct. We also like it because it reminds us of the flash-in-the-pan “carputer” trend from the late 00s where people in the pre-smartphone age were shoving all kinds of computing horsepower in their trunks.

2025 Component Abuse Challenge: A Bistable Flip-Flop With A Fuse

October 28, 2025 by 8 Comments

The flip-flop, in whichever of its several forms you encounter it, is a staple of logic design. Any time that you need to hold onto something, count, or shift bits, out it comes. We expect a flip-flop to be an integrated circuit if we use one, but most of us could knock one together with a couple of transistors.

You aren’t restricted to transistors of course, a relay will do just as well, but how about a fuse? [b.kainka] has made a functioning set/reset flip-flop using a pair of PTC self-resetting fuses.

The circuit is simplicity itself, a pair of incandescent bulbs in series, each in turn in parallel with a momentary action switch and a PTC fuse. On start-up both fuses are conducting, so one or other of them will do its job as a fuse and go high impedance. At that point its bulb will light and the other fuse will remain low impedance so its bulb will stay dark. Press the switch across the lit bulb for a few seconds however, and the circuit resets itself. The other fuse goes high impedance while the first fuse returns to low impedance, and the other bulb lights.

We’re not sure we can see much in the way of practical application for this circuit, but sometimes merely because you can is reason enough. 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

Know Audio: Lossy Compression Algorithms And Distortion

October 28, 2025 by 37 Comments

In previous episodes of this long-running series looking at the world of high-quality audio, at every point we’ve stayed in the real world of physical audio hardware. From the human ear to the loudspeaker, from the DAC to measuring distortion, this is all stuff that can happen on your bench or in your Hi-Fi rack.

We’re now going for the first time to diverge from the practical world of hardware into the theoretical world of mathematics, as we consider a very contentious topic in the world of audio. We live in a world in which it is now normal for audio to have some form of digital compression applied to it, some of which has an effect on what is played back through our speakers and headphones. When a compression algorithm changes what we hear, it’s distortion in audio terms, but how much is it distorted and how do we even measure that? It’s time to dive in and play with some audio files. Continue reading “Know Audio: Lossy Compression Algorithms And Distortion” →

There's an ATMega88 in that handsome case.

Give ATMega88 The Boot With This Retro Front Panel

October 28, 2025 by 14 Comments

It’s a truism that a computer must boot before it begins to operate. Nowadays that bootstrapping process is automatic, but in the case of the very first home computers, it was very much a hands-on affair. That’s what all those switches and blinkenlights are for on the front panel of the Altair 8800 — laboriously flicking each bit into memory as required to get your program going.

[Linus Åkesson] missed those very early days, and wanted to see what it was like, and clicking virtual switches on an emulator wasn’t going to cut it. He realized that he could set up an ATmega88 for front-panel booting, and proceeded to do just that.

The article linked above goes into good detail; for those of you who prefer video, we’ve embedded his presentation below.  They say the book is always better, but to get the full story, you’ll really want both in this case. The video contains a lot more context and build details, but neglects to mention some issues he had with programming that are detailed in the text. In short, the Write Page bit needs to be written to the Command register to use the page buffer. Which does make sense, but tripped [Linus] up at first.

Then again, this use case isn’t exactly detailed in the datasheet. ATmega88 is an old chip, but not Intel 8008 old, so that’s no surprise. Which is exactly what makes this a good hack! The only thing lacking is blinkenlights to allow one to see the contents of the registers. [Linus] discusses the idea of putting them in, but is apparently happy with this more minimalist approach.

We’ve seen the doughty Atmel chip hacked into everything from web-servers to washing machines, and even things that don’t start with “W”. As for the redoubtable [Linus], he’s most famous around these parts for his musical inventions and adventures with the Commodore 64.  Continue reading “Give ATMega88 The Boot With This Retro Front Panel” →

Analog Surround Sound Was Everywhere, But You Probably Didn’t Notice

October 28, 2025 by 21 Comments

These days, most of the media we consume is digital. We still watch movies and TV shows, but they’re all packaged in digital files that cram in many millions of pixels and as many audio channels as we could possibly desire.

Back in the day, though, engineering limitations meant that media on film or tape were limited to analog stereo audio at best. And yet, the masterminds at Dolby were able to create a surround sound format that could operate within those very limitations, turning two channels in to four. What started out as a cinematic format would bring surround sound to the home—all the way back in 1982!

Continue reading “Analog Surround Sound Was Everywhere, But You Probably Didn’t Notice” →

Mushrooms As Computer Memory

October 28, 2025 by 35 Comments

Fungi make up a massive, interconnected part of Earth’s ecosystems, yet they’re vastly underrepresented in research and public consciousness compared to plants and animals. That may change in the future though, as a group of researchers at The Ohio State University have found a way to use fungi as organic memristors — hinting at a possible future where fungal networks help power our computing devices.

A memristor is a passive electronic component whose resistance changes based on the voltage and current that has passed through it, which means it can effectively remember past electrical states even when power is removed. To create these circuit components with fungus, the researchers grew shiitake and button mushroom mycelium for these tests, dehydrated their samples for a number of days, and then attached electrodes to the samples. After misting them briefly to restore conductivity, the samples were exposed to various electrical wave forms at a range of voltages to determine how effective they were at performing the duties of a memristor. At one volt these systems were the most consistent, and they were even programmed to act like RAM where they achieved a frequency of almost 6 kHz and an accuracy of 90%.

In their paper, the research group notes a number of advantages to building fungal-based components like these, namely that they are much more environmentally friendly and don’t require the rare earth metals that typical circuit components do. They’re also easier to grow than other types of neural organoids, require less power, weigh less, and shiitake specifically is notable for its radiation resistance as well. Some work needs to be done to decrease the size required, and with time perhaps we’ll see more fungi-based electrical components like these.