It’s An Audio Distortion Analyzer, Just Not The One You Were Hoping For

An audio distortion analyzer is a specialist piece of analogue test equipment that usually costs a lot of money and can be hard to track down on the second hand market. Finding one is a moment of luck for the average engineer then, but [Thomas Scherrer OZ2CPU]’s discovery isn’t quite what he might have hoped for. Nonetheless, his Bang and Olufsen K3 Distortion meter DM1 from 1979 is still an interesting and high quality piece of test equipment, and the video below the break makes for a worthwhile watch.

Bang and Olufsen are best known for high-end design Hi-Fi units, thus it’s a surprise to find that in the past they also manufactured test equipment. This distortion meter isn’t a general purpose one, instead it’s designed to measure tape recorders in particular, and it uses an elegant technique. Instead of injecting a sine wave and removing it from what comes out in order to measure the products of the distortion, it records a 333 Hz sine wave onto a tape, then measures the strength of its 3rd harmonic at 1 kHz as an indication of distortion. It’s a working distortion meter made with clever analogue circuitry for a fraction of the cost of the more conventional models that HP would have sold you at the same time, even if it doesn’t give the same THD figure you might have been looking for.

If distortion interests you, it’s a subject we’ve looked at in the past.

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A 360° View Of A Classic Drive-In Speaker

Readers of a certain vintage no doubt have pleasant memories of drive-in theaters, and we are chuffed to see that a few hundred of these cinematic institutions endure today. While most theaters broadcast the audio on an FM station these days, the choice is still yours to use the chunky, often crackly speaker that attaches to the car window.

Seeking to relive the drive-in audio experience at home, [codemakesitgo] picked up a drive-in theater speaker on eBay and turned it into a Bluetooth device that sounds much better than it did in its weather-beaten days outside.

There isn’t a whole lot to this build — it’s essentially a new speaker cone, a Bluetooth receiver, an amp, and a battery. The real story is in the way that [codemakesitgo] uses Fusion360 to bring it all together.

After 3D scanning the case, [codemakesitgo] made sure each piece would fit, using a custom-built model of the new speaker and a 3D model of a custom PCB. Good thing, too, because there is barely enough clearance for the speaker. Be sure to check out the brief demo video after the break.

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Recycling Batteries With Bacteria

Vehicle battery recycling is going to be a big deal with all the electric cars hitting the roads. What if you could do it more effectively with the power of microbes? (via Electrek)

“Li-ion” vehicle batteries can be any of a number of different chemistries, with more complex cathode makeups, like NCM (LiNixMnyCo1-x-yO2), being understandably more complex to separate into their original constituents. Researchers and companies in the industry are hoping to find economically-viable ways to get these metals back for both the environmental and economic benefits a closed loop system could provide.

Researchers in the UK developed a method using two species of bacteria to precipitate Ni, Mn, and Co from the liquid leached from cathodes. Li remained in the liquid where it could be processed separately like that obtained in Li brine. Mn was precipitated first by S. oneidensis MR-1, and a following step removed Ni and Co with D. alaskensis G20. The researchers report that Ni and Co show promise for further separation via biological methods, but more research is required for this step.

If you’re looking for some more interesting ways bacteria can be harnessed for the energy system, checkout this microbial fuel cell, another using soil, and an enzyme derived from bacteria that can pull electricity from thin air.

Simulate A Better Termination

If you are making certain precision measurements, you know you need to terminate the connections with the right impedance, normally 50 ohms. Proper termination minimizes reflections on the line which can disturb measurements. Some instruments already have 50 ohm terminations, at least optionally. If not, you usually use little connector shells with the right resistor inside. [Joe Smith] decided to see if he could improve on the normal terminations using circuit simulation techniques. You can see a video of the work below.

In the process of testing, he also needs a resistive splitter, and, just like with the terminators, he shows you what’s going on inside. It was easy to compare since he had a scope that could independently set channels to have a 50-ohm termination or a 1 megaohm termination.

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Old Prius Gets Upgraded Batteries

So many of the batteries made today are lithium batteries of some sort, from mobile phones, laptops, and drones to electric cars and grid storage solutions. But this technology is relatively new; even as late as the 90s and early 00s the only widely-available batteries for things like power tools or the new hybrid vehicles coming on the market were nickel-metal hydride (NiMH). While it was good for the time, they don’t hold up to all of the advantages lithium has. There’s still plenty of hybrid vehicles on the road using these batteries, so if you’re driving an older Prius and want to give it a modern refresh, there’s a quick option to swap your old batteries.

Despite lithium technology being available for several decades, the switch to lithium for the Toyota Prius wasn’t instant, with many variants still using NiMH batteries as late as the 2020s largely because the NiMH batteries are less expensive and less maintenance-intensive than lithium batteries are. As these batteries lose capacity, the cars are still driveable but the advantages of the hybrid drivetrain won’t be as accessible anymore. The upgrade, from a company called Project Lithium, replaces these batteries with modern lithium technology that can improve the efficiency and performance of these cars even above their original capabilities since lithium batteries have more power density.

With the Toyota Prius being among the most reliable vehicles on the road thanks to the electric motor in the hybrid drivetrain taking a lot of stress off of the internal combustion engine, it’s often worth upgrading these old batteries to modern ones to squeeze every last mile from these workhorses as possible. With many of the replacement processes being almost as simple as lifting out an old battery and placing a new one in, it can be a no-brainer if that’s the only issue with the vehicle otherwise. This is also true of all-electric vehicles as well, although the process to replace the battery can be a little more involved.

Thanks to [JohnU] for the tip!

Hacking An NFC E-Paper Display From Waveshare With Mystery MCU

These days e-paper (eInk) displays are everywhere, with stores being one of the largest users of smaller, monochrome versions of these persistent displays. This has also made them a solid target of hackers who seek to not only reverse-engineer and reuse discarded ones, but also ones sold to consumers, with [Aaron Christophel] recently reverse-engineering and flashing custom firmware (GitHub source) to a Waveshare 2.13″ NFC-Powered E-Paper display.

What’s perhaps most notable is how locked-down and devoid of documentation these devices are. The board [Aaron] looked at did not have any markings on the main IC, and Waveshare did not provide more information other than the Android and iOS apps. This led to some matching of various NFC-enabled MCUs with the pinout, with the Chivotech TN2115S2 rolling out as the most likely candidate. This is an 8 MHz Cortex-M0 MCU with not only NFC, but also an energy harvesting feature (up to 300 mW), which is why this e-paper tag can update the display without external power or a battery.

With the Chivotech datasheet being rather sparse, more reverse-engineering needed to be done, which included dumping the firmware and exploring it with Ghidra. During this, the secret key was discovered to make the Flash writeable along with how to control the peripherals and display. With this knowledge it’s now possible to make this tag display update without being limited by manufacturer-supplied tools and software, making it infinitely more useful.

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Ask Hackaday: What Do You Do When You Can’t Solder?

Ah, soldering. It’s great for sticking surface mount parts to a PCB, and it’s really great for holding component legs in a plated through-hole. It also does a pretty great job of holding two spliced wires together.

With that said, it can be a bit of a fussy process. There are all manner of YouTube videos and image tutorials on the “properest” way to achieve this job. Maybe it’s the classic Lineman’s Splice, maybe it’s some NASA-approved method, or maybe it’s one of those ridiculous ones where you braid all the copper strands together, solder it all up, and then realize you’ve forgotten to put the heat shrink on first.

Sure, soldering’s all well and good. But what about some of the other ways to join a pair of wires?

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