Using an SMD capacitor as a clip for flash media on a circuit board.

SMD Capacitor Doubles As Cheap SD Card Latch

July 4, 2025 by John Elliot V 40 Comments

Here’s a clever hack. Simple, elegant, and eminently cost-effective: using an SMD capacitor to hold your flash media in place!

This is a hack that can pretty much be summed up with just the image at the top of the page — a carefully placed SMD capacitor soldered to a routed tab makes for an extremely cost effective locking mechanism for the nearby SD card slot. There’s just enough flexibility to easily move the capacitor when its time to insert or eject your media.

It’s worth noting that the capacitor in this example doesn’t even appear to be electrically connected to anything. But there’s also no reason you couldn’t position one of the capacitors in your existing bill of materials (BOM). This form of mechanical support will be much cheaper than special purpose clips or mounts. Not a big deal for low-volume projects, but if you’re going high-volume this is definitely something to keep in mind.

If you’re just getting started with SMD capacitors then one of the first things to learn is how to solder them. Also, if you’re hoping to salvage them then try to look for newer equipment which is more likely to have SMD components than through-hole. If you’re planning to use your capacitors for… “capacitance” (how quaint), you can start by learning the basics. And if you want to know everything you can learn about the history of capacitors, too.

Thanks to [JohnU] for writing in to let us know about this one. Have your own natty hacks? Let us know on the tipsline!

Linear Solar Chargers For Lithium Capacitors

June 26, 2025 by Bryan Cockfield 24 Comments

For as versatile and inexpensive as switch-mode power supplies are at all kinds of different tasks, they’re not always the ideal choice for every DC-DC circuit. Although they can do almost any job in this arena, they tend to have high parts counts, higher complexity, and higher cost than some alternatives. [Jasper] set out to test some alternative linear chargers called low dropout regulators (LDOs) for small-scale charging of lithium ion capacitors against those more traditional switch-mode options.

The application here is specifically very small solar cells in outdoor applications, which are charging lithium ion capacitors instead of batteries. These capacitors have a number of benefits over batteries including a higher number of discharge-recharge cycles and a greater tolerance of temperature extremes, so they can be better off in outdoor installations like these. [Jasper]’s findings with using these generally hold that it’s a better value to install a slightly larger solar cell and use the LDO regulator rather than using a smaller cell and a more expensive switch-mode regulator. The key, though, is to size the LDO so that the voltage of the input is very close to the voltage of the output, which will minimize losses.

With unlimited time or money, good design can become less of an issue. In this case, however, saving a few percentage points in efficiency may not be worth the added cost and complexity of a slightly more efficient circuit, especially if the application will be scaled up for mass production. If switched mode really is required for some specific application, though, be sure to design one that’s not terribly noisy.

Kludge Compensates For Kaput Component With Contemporary Capacitor

June 16, 2025 by Seth Mabbott 14 Comments

It is a well-known reality of rescuing certain older electronic devices that, at some point, you’re likely going to have to replace a busted capacitor. This is the stage [Kevin] is at in the 3rd installment in his saga of reviving a 50-year-old Military Tektronix oscilloscope.

[Kevin] recently discovered a failed capacitor in the power supply for this vintage analog scope. Having identified and removed the culprit, it was time to find a way to replace the faulty component with a modern equivalent. The original capacitor is out of fashion to the degree that a perfect replacement would be impractical and likely not desirable. This job would call for a bit of adaptation.

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Hackaday Podcast Episode 313: Capacitor Plague, Wireless Power, And Tiny Everything

March 21, 2025 by Jenny List 3 Comments

We’re firmly in Europe this week on the Hackaday podcast, as Elliot Williams and Jenny List are freshly returned from Berlin and Hackaday Europe. A few days of mingling with the Hackaday community, going through mild panic over badges and SAOs, and enjoying the unique atmosphere of that city.

After discussing the weekend’s festivities we dive right into the hacks, touching on the coolest of thermal cameras, wildly inefficient but very entertaining wireless power transfer, and a restrospective on the capacitor plague from the early 2000s. Was it industrial espionage gone wrong, or something else? We also take a moment to consider spring PCB cnnectors, as used by both one of the Hackaday Europe SAOs, and a rather neat PCB resistance decade box, before looking at a tryly astounding PCB blinky that sets a new miniaturisation standard.

In our quick roundup the standouts are a 1970s British kit synthesiser and an emulated 6502 system written in shell script, and in the can’t-miss section we look at a new contender fro the smallest microcontroller, and the posibility that a century of waste coal ash may conceal a fortune in rare earth elements.

Follow the link below, to listen along!

Want the podcast in MP3? Get it in MP3!

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The Capacitor Plague Of The Early 2000s

March 18, 2025 by Maya Posch 54 Comments

Somewhere between the period of 1999 and 2007 a plague swept through the world, devastating lives and businesses. Identified by a scourge of electrolytic capacitors violently exploding or splurging their liquid electrolyte guts all over the PCB, it led to a lot of finger pointing and accusations of stolen electrolyte formulas. In a recent video by [Asianometry] this story is summarized.

Blown electrolytic capacitors. (Credit: Jens Both, Wikimedia)

The bad electrolyte in the faulty capacitors lacked a suitable depolarizer, which resulted in more gas being produced, ultimately leading to build-up of pressure and the capacitor ultimately failing in a way that could be rather benign if the scored top worked as vent, or violently if not.

Other critical elements in the electrolyte are passivators, to protect the aluminium against the electrolyte’s effects. Although often blamed on a single employee stealing an (incomplete) Rubycon electrolyte formula, the video questions this narrative, as the problem was too widespread.

More likely it coincided with the introduction of low-ESR electrolytic capacitors, along with computers becoming increasingly more power-hungry, and thus stressing the capacitors in a much warmer environment than in the early 1990s. Combine this with the presence of counterfeit capacitors in the market and the truth of what happened to cause the Capacitor Plague probably involves a bit from each column, a narrative that seems to be the general consensus.

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Hackaday Podcast Episode 306: Bambu Hacks, AI Strikes Back, John Deere Gets Sued, And All About Capacitors

January 31, 2025 by Dan Maloney No comments

It was Dan and Elliot behind the microphones today for a transatlantic look at the week in hacks. There was a bucket of news about AI, kicked off by Deepseek suddenly coming into the zeitgeist and scaring the pants off investors for… reasons? No matter, we’re more interested in the tech anyway, such as a deep dive into deep space communications from a backyard antenna farm that’s carefully calibrated to give the HOA fits. We got down and dirty with capacitors, twice even, and looked at a clever way to stuff two websites into one QR code. It’s all Taylor, all the time on every channel of the FM band, which we don’t recommend you do (for multiple reasons) but it’s nice to know you can. Plus, great kinetic art project, but that tooling deserves a chef’s kiss. Finally, we wrap up with our Can’t Miss articles where Jenny roots for the right to repair, and Al gives us the finger(1).

Download the zero-calorie MP3.

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Crystal structure of a monolayer of transition metal dichalcogenide.(Credit: 3113Ian, Wikimedia)

Transition-Metal Dichalcogenides: Super-Conducting, Super-Capacitor Semiconductors

January 28, 2025 by Maya Posch 3 Comments

Transition-metal dichalcogenides (TMDs) are the subject of an emerging field in semiconductor research, with these materials offering a range of useful properties that include not only semiconductor applications, but also in superconducting material research and in supercapacitors. A recent number of papers have been published on these latter two applications, with [Rui] et al. demonstrating superconductivity in (InSe₂)_xNbSe₂. The superconducting transition occurred at 11.6 K with ambient pressure.

Two review papers on transition metal sulfide TMDs as supercapacitor electrodes were also recently published by [Mohammad Shariq] et al. and [Can Zhang] et al. showing it to be a highly promising material owing to strong redox properties. As usual there are plenty of challenges to bring something like TMDs from the laboratory to a production line, but TMDs (really TMD monolayers) have already seen structures like field effect transistors (FETs) made with them, and used in sensing applications.

TMDs consist of a transition-metal (M, e.g. molybdenum, tungsten) and a chalcogen atom (X, e.g. sulfur) in a monolayer with two X atoms (yellow in the above image) encapsulating a single M atom (black). Much like with other monolayers like graphene, molybdenene and goldene, it is this configuration that gives rise to unexpected properties. In the case of TMDs, some have a direct band gap, making them very suitable for transistors and perhaps most interestingly also for directly growing 3D semiconductor structures.

Heading image: Crystal structure of a monolayer of transition metal dichalcogenide.(Credit: 3113Ian, Wikimedia)