Author: Dan Maloney

3372 Articles

Exploring Cheap Tantalum Caps Of Mysterious Provenance

July 22, 2024 by 27 Comments

We’ve all heard about the perils of counterfeit chips, and more than a few of us have probably been bitten by those scruple-free types who run random chips through a laser marker and foist them off as something they’re not. Honestly, we’ve never understood the business model here — it seems like the counterfeiters spend almost as much time and effort faking chips as they would just getting the real ones. But we digress.

Unfortunately, integrated circuits aren’t the only parts that can be profitably faked, as [Amateur Hardware Repair] shows us with this look at questionable tantalum capacitors. In the market for some tantalums for a repair project, the offerings at AliExpress proved too tempting to resist, despite being advertised alongside 1,000 gram gold bars for $121 each. Wisely, he also ordered samples from more reputable dealers like LCSC, DigiKey, and Mouser, although not at the same improbably low unit price.

It was pretty much clear where this would be going just from the shipping. While the parts houses all shipped their tantalums in Mylar bags with humidity indicators, with all but LCSC including a desiccant pack, the AliExpress package came carefully enrobed in — plastic cling wrap? The Ali tantalums were also physically different from the other parts: they were considerably smaller, the leads seemed a little chowdered up, and the package markings were quite messy and somewhat illegible. But the proof is in the testing, and while all the more expensive parts tested fine in terms of capacitance and equivalent series resistance, the caps of unknown provenance had ESRs in the 30 milliohm range, three to five times what the reputable caps measured.

None of this is to say that there aren’t some screaming deals on marketplaces like AliExpress, Amazon, and eBay, of course. It’s not even necessarily proof that these parts were in fact counterfeit, it could be that they were just surplus parts that hadn’t been stored under controlled conditions. But you get what you pay for, and as noted in the comments below the video, a lot of what you’re paying for at the parts houses is lot tracebility.

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Coax Stub Filters Demystified

July 21, 2024 by 9 Comments

Unless you hold a First Degree RF Wizard rating, chances are good that coax stubs seem a bit baffling to you. They look for all the world like short circuits or open circuits, and yet work their magic and act to match feedline impedances or even as bandpass filters. Pretty interesting behavior from a little piece of coaxial cable.

If you’ve ever wondered how stub filters do their thing, [Fesz] has you covered. His latest video concentrates on practical filters made from quarter-wavelength and half-wavelength stubs. Starting with LTspice simulations, he walks through the different behaviors of open-circuit and short-circuit stubs, as well as what happens when multiple stubs are added to the same feedline. He also covers a nifty online calculator that makes it easy to come up with stub lengths based on things like the velocity factor and characteristic impedance of the coax.

It’s never just about simulations with [Fesz], though, so he presents a real-world stub filter for FM broadcast signals on the 2-meter amateur radio band. The final design required multiple stubs to get 30 dB of attenuation from 88 MHz to 108 MHz, and the filter seemed fairly sensitive to the physical position of the stubs relative to each other. Also, the filter needed a little LC matching circuit to move the passband frequency to the center of the 2-meter band. All the details are in the video below.

It’s pretty cool to see what can be accomplished with just a couple of offcuts of coax. Plus, getting some of the theory behind those funny little features on PCBs that handle microwave frequencies is a nice bonus. This microwave frequency doubler is a nice example of what stubs can do.

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Hackaday Links: July 21, 2024

July 21, 2024 by 20 Comments

When monitors around the world display a “Blue Screen of Death” and you know it’s probably your fault, it’s got to be a terrible, horrible, no good, very bad day at work. That’s likely the situation inside CrowdStrike this weekend, as engineers at the cybersecurity provider struggle to recover from an update rollout that went very, very badly indeed. The rollout, which affected enterprise-level Windows 10 and 11 hosts running their flagship Falcon Sensor product, resulted in machines going into a boot loop or just dropping into restore mode, leaving hapless millions to stare at the dreaded BSOD screen on everything from POS terminals to transit ticketing systems.

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Welding Wood Is As Simple As Rubbing Two Sticks Together

July 21, 2024 by 12 Comments

Can you weld wood? It seems like a silly question — if you throw a couple of pieces of oak on the welding table and whip out the TIG torch, you know nothing is going to happen. But as [Action Lab] shows us in the video below, welding wood is technically possible, if not very practical.

Since experiments like this sometimes try to stretch things a bit, it probably pays to define welding as a process that melts two materials at their interface and fuses them together as the molten material solidifies. That would seem to pose a problem for wood, which just burns when heated. But as [Action Lab] points out, it’s the volatile gases released from wood as it is heated that actually burn, and the natural polymers that are decomposed by the heat to release these gases have a glass transition temperature just like any other polymer. You just have to heat wood enough to reach that temperature without actually bursting the wood into flames.

His answer is one of the oldest technologies we have: rubbing two sticks together. By chucking a hardwood peg into a hand drill and spinning it into a slightly undersized hole in a stick of oak, he created enough heat and pressure to partially melt the polymers at the interface. When allowed to cool, the polymers fuse together, and voila! Welded wood. Cutting his welded wood along the joint reveals a thin layer of material that obviously underwent a phase change, so he dug into this phenomenon a bit and discovered research into melting and welding wood, which concludes that the melted material is primarily lignin, a phenolic biopolymer found in the cell walls of wood.

[Action Lab] follows up with an experiment where he heats bent wood in a vacuum chamber with a laser to lock the bend in place. The experiment was somewhat less convincing but got us thinking about other ways to exclude oxygen from the “weld pool,” such as flooding the area with argon. That’s exactly what’s done in TIG welding, after all. Continue reading “Welding Wood Is As Simple As Rubbing Two Sticks Together” →

Hackaday Podcast Episode 280: TV Tubes As Amplifiers, Smart Tech In Sportsballs, And Adrian Gives Us The Fingie

July 19, 2024 by 3 Comments

Despite the summer doldrums, it was another big week in the hacking world, and Elliot sat down with Dan for a rundown. Come along for the ride as Dan betrays his total ignorance of soccer/football, much to Elliot’s amusement. But it’s all about keeping the human factor in sports, so we suppose it was worth it. Less controversially, we ogled over a display of PCB repair heroics, analyzed a reverse engineering effort that got really lucky, and took a look at an adorable one-transistor ham transceiver. We also talked about ants doing surgery, picking locks with nitric acid, a damn cute dam, and how to build one of the world’s largest machines from scratch in under a century. Plus, we answered the burning question: can a CRT be used as an audio amplifier? Yes, kind of, but please don’t let the audiophiles know or we’ll never hear the end of it.

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Retrotechtacular: Ford Model T Wheels, Start To Finish

July 18, 2024 by 20 Comments

There’s no doubt that you’ll instantly recognize clips from the video below, as they’ve been used over and over for more than 100 years to illustrate the development of the assembly line. But those brief clips never told the whole story about just how much effort Ford was forced to put into manufacturing just one component of their iconic Model T: the wheels.

An in-house production of Ford Motors, this film isn’t dated, at least not obviously. And with the production of Model T cars using wooden spoked artillery-style wheels stretching from 1908 to 1925, it’s not easy to guess when the film was made. But judging by the clothing styles of the many hundreds of men and boys working in the River Rouge wheel shop, we’d venture a guess at 1920 or so.

Production of the wooden wheels began with turning club-shaped spokes from wooden blanks — ash, at a guess — and drying them in a kiln for more than three weeks. While they’re cooking, a different line steam-bends hickory into two semicircular felloes that will form the wheel’s rim. The number of different steps needed to shape the fourteen pieces of wood needed for each wheel is astonishing. Aside from the initial shaping, the spokes need to be mitered on the hub end to fit snugly together and have a tenon machined on the rim end. The felloes undergo multiple steps of drilling, trimming, and chamfering before they’re ready to receive the spokes.

The first steel component is a tire, which rolls down out of a furnace that heats and expands it before the wooden wheel is pressed into it. More holes are drilled and more steel is added; plates to reinforce the hub, nuts and bolts to hold everything together, and brake drums for the rear wheels. The hubs also had bearing races built right into them, which were filled with steel balls right on the line. How these unsealed bearings were protected during later sanding and grinding operations, not to mention the final painting step, which required a bath in asphalt paint and spinning the wheel to fling off the excess, is a mystery.

Welded steel spoked wheels replaced their wooden counterparts in the last two model years for the T, even though other car manufacturers had already started using more easily mass-produced stamped steel disc wheels in the mid-1920s. Given the massive infrastructure that the world’s largest car manufacturer at the time devoted to spoked wheel production, it’s easy to see why. But Ford eventually saw the light and moved away from spoked wheels for most cars. We can’t help but wonder what became of the army of workers, but it probably wasn’t good. So turn the wheels of progress.

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Flexures Make Robotic Fingers Simpler To Print

July 16, 2024 by 6 Comments

Designing an anthropomorphic robotic hand seems to make a lot of sense — right up until the point that you realize just how complex the human hand is. What works well in bone and sinew often doesn’t translate well to servos and sensors, and even building a single mechanical finger can require dozens of parts.

Or, if you’re as clever about things as [Adrian Perez] is, only one part. His print-in-place robotic finger, adorably dubbed “Fingie,” is a huge step toward simplifying anthropomorphic manipulators. Fingie is printed in PLA and uses flexures for the three main joints of the finger, each of which consists of two separate and opposed coil springs. The flexures allow the phalanges to bend relative to each other in response to the motion of three separate tendons that extend through a channel on the palmar aspect of the finger, very much like the real thing.

The flexures eliminate the need for bearings at each joint and greatly decrease the complexity of the finger, but the model isn’t perfect. As [Adrian] points out, the off-center attachment for the tendons makes the finger tend to curl when the joints are in flexion, which isn’t how real fingers work. That should be a pretty easy fix, though. And while we appreciate the “one and done” nature of this print, we’d almost like to see the strap-like print-in-place tendons replaced with pieces of PLA filament added as a post-processing step, to make the finger more compact and perhaps easier to control.

Despite the shortcomings, and keeping in mind that this is clearly a proof of concept, we really like where [Adrian] is going with this, and we’re looking forward to seeing a hand with five Fingies, or four Fingies and a Thumbie. It stands to be vastly simpler than something like [Will Cogley]’s biomimetic hand, which while an absolute masterpiece of design, is pretty daunting for most of us to reproduce.

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