Precision Reference Puts Interesting Part To Work

February 11, 2025 by Dan Maloney 8 Comments

Interesting parts make for interesting projects, and this nifty precision voltage reference has some pretty cool parts, not to mention an interesting test jig.

The heart of [Gaurav Singh]’s voltage reference is an ADR1399, precision shunt reference from Analog Devices. The datasheet makes for pretty good reading and reveals that there’s a lot going on inside the TO-49 case, which looks unusually large thanks to a thick plastic coat. The insulation is needed for thermal stability for the heated Zener diode reference. The device also has a couple of op-amps built in, one that provides closed-loop voltage control and another that keeps the internal temperature at a toasty 95°C. The result is a reference that’s stable over a wide range of operating conditions.

[Gaurav]’s implementation maximizes this special part’s capabilities while making it convenient to use. The PCB has a precision linear regulator that accepts an input voltage from 16 V to 20 V, plus a boost converter that lets you power it from USB-C. The board itself is carefully designed to minimize thermal and mechanical stress, with the ADR1399 separated from the bulk of the board with wide slots. The first video below covers the design and construction of an earlier rev of the board.

One problem that [Gaurav] ran into with these boards was the need to age the reference with an extended period of operation. To aid in that, he built a modular test jig that completed PCBs can be snapped into for a few weeks of breaking in. The jigs attach to a PCB with pogo pins, which mate to test points and provide feedback on the aging process. See the second video for more details on that.

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Breaking: USPS Halts Inbound Packages From China And Hong Kong Posts

February 5, 2025 by Tom Nardi 104 Comments

Update: The USPS has now resumed acceptance of inbound packages from China. According to the updated Service Alert, they are currently working with Customs and Border Protection to “implement an efficient collection mechanism for the new China tariffs.’

Some troubling news hit overnight as the United States Post Office announced via a terse “Service Alert” that they would suspend acceptance of inbound parcels from China and Hong Kong Posts, effective immediately.

The Alert calls it a temporary suspension, but gives no timeline on when service will be restored. While details are still coming together, it seems likely that this suspension is part of the Trump administration’s Chinese tariff package, which went into effect at midnight.

Specifically, the administration looks to close the “de minimis” exemption — a loophole which allowed packages valued under $800 USD to pass through customs without having to pay any duties or fees. Those packages will now not only be subject to the overall 10% tax imposed by the new tariff package, but will now have to be formally processed through customs, potentially tacking on even more taxes and fees.

The end result is that not only will your next order of parts from AliExpress be more expensive, but it’s likely to take even longer to arrive at your door. Of course, this should come as no surprise. At the end of the day, this is precisely what the administration aims to accomplish with the new tariffs — if purchasing goods from overseas is suddenly a less attractive option than it was previously, it will be a boon to domestic suppliers. That said, some components will be imported from China regardless of who you order them from, so those prices are still going to increase.

Other carriers such as FedEx and UPS will also have to follow these new rules, but at the time of this writing, neither service had released a statement about how they intend to comply.

How 3D Printing Helps Bring USS Cod Memorial To Life

February 5, 2025 by Tom Nardi 3 Comments

The USS Cod is a Gato-class submarine that saw combat in the Second World War and today operates as a museum ship in Cleveland, Ohio. While many other surviving WWII-era subs were cut into pieces or otherwise modified for public display, Cod is notable for being intact and still in her wartime configuration. It’s considered to be one of the finest submarine restorations in the world, and in a recent video from their official YouTube page, we get a look at how 3D printing is used to keep the 82 year old submarine looking battle-ready.

In the video below, President of the USS Cod Submarine Memorial [Paul Farace] is joined by one of the volunteers who’s been designing and printing parts aboard the submarine. While the Cod is in remarkable condition overall, there’s no shortage of odd bits and pieces that have gone missing over the sub’s decades of service.

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Homebrew Foil And Oil Caps Change Your Guitar’s Tone

February 4, 2025 by Dan Maloney 47 Comments

How any string instrument sounds depends on hundreds of factors; even the tiniest details matter. Seemingly inconsequential things like whether the tree that the wood came from grew on the north slope or south slope of a particular valley make a difference, at least to the trained ear. Add electronics into the mix, as with electric guitars, and that’s a whole other level of choices that directly influence the sound.

To experiment with that, [Mark Gutierrez] tried rolling some home-brew capacitors for his electric guitar. The cap in question is part of the guitar’s tone circuit, which along with a potentiometer forms a variable low-pass filter. A rich folklore has developed over the years around these circuits and the best way to implement them, and there are any number of commercially available capacitors with the appropriate mojo you can use, for a price.

[Mark]’s take on the tone cap is made with two narrow strips of regular aluminum foil separated by two wider strips of tissue paper, the kind that finds its way into shirt boxes at Christmas. Each of the foil strips gets wrapped around and crimped to a wire lead before the paper is sandwiched between. The whole thing is rolled up into a loose cylinder and soaked in mineral oil, which serves as a dielectric.

To hold the oily jelly roll together, [Mark] tried both and outer skin of heat-shrink tubing with the ends sealed by hot glue, and a 3D printed cylinder. He also experimented with a wax coating to keep the oily bits contained. The video below shows the build process as well as tests of the homebrew cap against a $28 commercial equivalent. There’s a clear difference in tone compared to switching the cap out of the circuit, as well as an audible difference in tone between the two caps. We’ll leave the discussion of which sounds better to those with more qualified ears; fools rush in, after all.

Whatever you think of the sound, it’s pretty cool that you can make working capacitors so easily. Just remember to mark the outer foil lead, lest you spoil everything.

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Film Capacitors Can Go In The Wrong Way Round? Who Knew!

January 27, 2025 by Jenny List 34 Comments

You can work with a part for many decades, and still learn something new about it. At least we can, and we don’t mind admitting it. Take film capacitors — we all know they aren’t a polarized part like an electrolytic capacitor is, but as [TheDannVal] points out, that doesn’t mean both their leads are the same.

This might sound counterintuitive, but if you consider for a moment their construction it makes sense. A film capacitor is made from two strips of foil with a strip of plastic film between then, rolled up tightly into a cylinder. One of the pieces of foil that forms one side of the capacitor ends up on the outside of the cylinder, and thus forms the shield for the other. Thus if that side isn’t connected to the lower impedance side of whichever circuitry it resides in, it can pick up noise, while the inside strip of foil can not. It’s so obvious when demonstrated, but we have to admit to never having considered it before. Some film capacitors have a line marked on them to denote the connection forming the shield, for those that don’t he provides a couple of methods for detecting it.

The full video is below the break, and maybe you too can now pay attention to your capacitors for lower noise audio circuitry.

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The ESP32-C5, Finally Espressif Goes Dual-Band

January 26, 2025 by Jenny List 21 Comments

The ESP32 series of microcontrollers have been with us for quite a few years now, providing a powerful processor and wireless connectivity for not a huge outlay. We’ve seen a bunch of versions over the years with both Tensilica and RISC-V cores, but so far the ones with radios have all only serviced 2.4 GHz WiFi. That’s about to change to include 5GHz with the new C5 variant though, and [Andreas Spiess] has been lucky enough to get his hands on a prototype dev kit

It’s very similar to the C6, which we’re already used to beyond the dual-band 2.4GHz and 5GHz radio from a software point of view. The C5 is so new that the company has yet to incorporate the new chip into the Arduino IDE. He shows it working and detecting both networks though, and speculates a little about its eventual marketing.

Interesting to us is the dual-band antenna, with branches for both frequencies on the same PCB. We’d be interested to see the real-world performance of this, and also whether they produce a version with separate outputs for each band. The full video is below the break. In the meantime, watch out for this chip appearing on the market.

It’s not the only Espresif chip we’re anticipating at the moment.

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Putting Cheap Motorcycle Tachometers To Work

January 18, 2025 by Tom Nardi 15 Comments

With so much data being thrown at our eyeballs these days, it’s worryingly easy for the actually important stuff to slip by occasionally. So when [Liam Jackson] wanted a way to visualize the number of test failures popping up in the continuous integration system at work, he went with a novel but effective solution — universal motorcycle tachometers.

It turns out these little gauges can be had for under $10 a piece from the usual overseas retailers, and are very easy to drive with a microcontroller. As [Liam] explains, all you need to do other than providing them with 12 volts, is feed them a PWM signal. Even though the gauges are designed for a 12 V system, they apparently don’t have any problem responding to the 5 V logic level from the Arduino’s pins.

As for the frequency he says that 1,000 RPM corresponds to 16.66 Hz, so you can just multiply up from there to show whatever number you wish. That said, [Liam] warns that the gauges draw several hundred milliamps once the needle gets into the two digit range, so keep that in mind. Conveniently, those number happen to be in red anyway…

For his particular application, [Liam] put three of the gauges together to create a very handsome dashboard. If you want to recreate his setup exactly he’s made the STLs available for the gauge cluster housing. Note the small OLED at the center, this offers a way to show a bit more context than the three analog gauges alone can express, especially if you’ve got an application where you might be switching between multiple data sources.

Over the years we’ve seen several projects that repurposed analog gauges of various types, often for showing computer performance, but they generally involved having to drive the galvanometers directly. That these tachometers can simply be fed a simple digital signal should make implementing them into your project much easier.