Author: Dan Maloney

2976 Articles

Multiply Your Multimeter With Relays And USB

April 2, 2024 by 10 Comments

Multimeters are a bit like potato chips: you can’t have just one. But they’re a lot more expensive than potato chips, especially the good ones, and while it’s tempting to just go get another one when you need to make multiple measurements, sometimes it’s not practical. That’s why something like this 2×4 relay-based multiplexer might be a handy addition to your bench

In this age of electronics plenty, you’d think that a simple USB relay board would be easy enough to lay hands on. But [Petteri Aimonen] had enough trouble finding a decent one that it became easier to just roll one up from scratch. His goal was to switch both the positive and negative test leads from up to four instruments to a common set of outputs, and to have two independent switching banks, for those times when four-lead measurements are needed. The choice of relay was important; [Petteri] settled on a Panasonic DPDT signal relay with low wetting current contacts and a low-current coil. The coils are driven by a TBD62783A 8-channel driver chip, while an STM32 takes care of USB duties.

The mechanical design of this multiplexer is just as slick as the electrical. [Petteri] designed the PCB to act as the cover for a standard Hammond project box, so all the traces and SMD components are mounted on the back. That just leaves the forest of banana-plug binding posts on the front, along with a couple of pushbuttons for manual input switching and nicely silkscreened labels. The multiplexer is controlled over USB using the SCPI protocol, which happily includes an instrument class for signal switchers.

We think the fit and finish on this one is fantastic, as is usual with one of [Petteri]’s builds. You’ll probably recall his calibrated current reference or his snazzy differential probe.

Mining And Refining: Tungsten

April 2, 2024 by 16 Comments

Our metallurgical history is a little bit like a game of Rock, Paper, Scissors, only without the paper; we’re always looking for something hard enough to cut whatever the current hardest metal is. We started with copper, the first metal to be mined and refined. But then we needed something to cut copper, so we ended up with alloys like bronze, which demanded harder metals like iron, and eventually this arms race of cutting led us to steel, the king of metals.

But even a king needs someone to keep him in check, and while steel can be used to make tools hard enough to cut itself, there’s something even better for the job: tungsten, or more specifically tungsten carbide. We produced almost 120,000 tonnes of tungsten in 2022, much of which was directed to the manufacture of tungsten carbide tooling. Tungsten has the highest melting point known, 3,422 °C, and is an extremely dense, hard, and tough metal. Its properties make it an indispensible industrial metal, and it’s next up in our “Mining and Refining” series.

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6502 Hacking Hack Chat

April 1, 2024 by 5 Comments

Join us on Wednesday, April 3rd at noon Pacific for the 6502 Hacking Hack Chat with Anders Nielsen!

Back in the early days of the personal computing revolution, you could have any chip you wanted…as long as it was 8-bits. We’ve come a long way since then, and while nobody seriously hopes for a wholesale return to the time when a Commodore 64 or Apple II was the home computing power play, there’s still a lot to be said for the seat-of-the-pants feeling of the day. Our engineering forebears had their work cut out for them, and building the home PC revolution from the ground up with microprocessors that by today’s standards were laughably limited is something worth celebrating.

join-hack-chatEvery retrocomputing enthusiast has their own favorite chip, and for Anders, it’s obviously the 6502 — enough to give birth to his 65uino project, which put the storied microprocessor at the heart of an Arduino pin-compatible microcontroller. It’s a neat project that seems to have caught a lot of people’s imaginations and opened up a world of hardware and software hacks that modern hardware just doesn’t need.

Getting closer to the silicon is the goal of retrocomputing, and Anders is making it easy to get involved. And we’re lucky enough to have him stop by the Hack Chat to talk all about teaching the 6502 some 21st-century tricks. Stop by and join in the discussion, and maybe you’ll catch the 8-bit bug too.

Our Hack Chats are live community events in the Hackaday.io Hack Chat group messaging. This week we’ll be sitting down on Wednesday, April 3 at 12:00 PM Pacific time. If time zones have you tied up, we have a handy time zone converter.

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Hackaday Links: March 31, 2024

March 31, 2024 by 6 Comments

Battlelines are being drawn in Canada over the lowly Flipper Zero, a device seen by some as an existential threat to motor vehicle owners across the Great White North. The story started a month or so ago, when someone in the government floated the idea of banning devices that could be “used to steal vehicles by copying the wireless signals for remote keyless entry.” The Flipper Zero was singled out as an example of such a nefarious device, even though relatively few vehicles on the road today can be boosted using the simple replay attack that a Flipper is capable of, and the ones that are vulnerable to this attack aren’t all that desirable — apologies to the 1993 Camry, of course. With that threat hanging in the air, the folks over at Flipper Devices started a Change.org petition to educate people about the misperceptions surrounding the Flipper Zero’s capabilities, and to urge the Canadian government to reconsider their position on devices intended to explore the RF spectrum. That last bit is important, since transmit-capable SDR devices like the HackRF could fall afoul of a broad interpretation of the proposed ban; heck, even a receive-only SDR dongle might be construed as a restricted device. We’re generally not much for petitions, but this case might represent an exception. “First they came for the Flipper Zero, but I did nothing because I don’t have a Flipper Zero…”

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How Much Bandwidth Does CW Really Occupy?

March 30, 2024 by 47 Comments

Amateur radio license exams typically have a question about the bandwidths taken up by various modulation types. The concept behind the question is pretty obvious — as guardians of the spectrum, operators really should know how much space each emission type occupies. As a result, the budding ham is left knowing that continuous wave (CW) signals take up a mere 150 Hertz of precious bandwidth.

But is that really the case? And what does the bandwidth of a CW signal even mean, anyway? To understand that, we turn to [Alan (W2AEW)] and his in-depth look at CW bandwidth. But first, one needs to see that CW signals are a bit special. To send Morse code, the transmitter is not generating a tone for the dits and dahs and modulating a carrier wave, rather, the “naked” carrier is just being turned on and off by the operator using the transmitter’s keyer. The audio tone you hear results from mixing the carrier wave with the output of a separate oscillator in the receiver to create a beat frequency in the audio range.

That seems to suggest that CW signals occupy zero bandwidth since no information is modulated onto the carrier. But as [Alan] explains, the action of keying the transmitter imposes a low-frequency square wave on the carrier, so the occupied bandwidth of the signal depends on how fast the operator is sending, as well as the RF rise and fall time. His demonstration starts with a signal generator modulating a 14 MHz RF signal with a simple square wave at a 50% duty cycle. By controlling the keying frequency, he mimics different code speeds from 15 to 40 words per minute, and his fancy scope measures the occupied bandwidth at each speed. He’s also able to change the rise and fall time of the square wave, which turns out to have a huge effect on bandwidth; the faster the rise-fall, the larger the bandwidth.

It’s a surprising result given the stock “150 Hertz” answer on the license exam; in fact, none of the scenarios [Allen] tested came close to that canonical figure. It’s another great example of the subtle but important details of radio that [Alan] specializes in explaining.

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Electrospinning Artificial Heart Valves

March 29, 2024 by 10 Comments

When you think about additive manufacturing, thoughts naturally turn to that hot-glue squirting CNC machine sitting on your bench and squeezing whatever plastic doodad you need. But 3D printing isn’t the only way to build polymer structures, as [Riley] shows us with this fascinating attempt to create electrospun heart valves.

Now, you may never have heard of electrospinning, but we’ll venture a guess that as soon as you see what it entails, you’ll have a “Why didn’t I think of that?” moment. As [Riley] explains, electrospinning uses an electric field to build structures from fine threads of liquid polymer solution — he uses polycaprolactone (PCL), a biodegradable polyester we’ve seen used in other medical applications, which he dissolves in acetone. He loads it into a syringe, attaches the positive terminal of a high-voltage power supply to the hypodermic needle, and the negative terminal to a sheet of aluminum foil. The charge turns the PCL droplets into fine threads that accumulate on the foil; once the solvent flashes off, what’s left is a gossamer layer of non-woven plastic fabric.

To explore the uses of this material, [Riley] chose to make an artificial heart valve. This required a 3D-printed framework with three prongs, painted with conductive paint. He tried a few variations on the design before settling on a two-piece armature affixed to a rotating shaft. The PCL accumulates on the form, creating a one-piece structure that can be gingerly slipped off thanks to a little silicon grease used as a release agent.

The results are pretty impressive. The structure bears a strong resemblance to an artificial tricuspid heart valve, with three delicate leaves suspended between the upright prongs. It’s just a proof of concept, of course, but it’s a great demonstration of the potential of electrospinning, as well as an eye-opening look at what else additive manufacturing has to offer.

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Hackaday Podcast Episode 264: Cheap Minimills, 65-in-1 Electronics, And Time On Moon

March 29, 2024 by 5 Comments

It was Dan’s turn behind the mic with Elliot this time as we uncovered the latest from the world of hacking, and what an eclectic mix it was. It was slightly heavy on machining, with a look at mini-mills that are better than nothing, and a DIY DRO that’s A-OK. We also kicked the nostalgia bucket over — whatever that means — and got a new twist on the old “65-in-1” concept, found hidden code in 80s music, and looked at color TV in the US and how it got that way. We’ve got ample alliteration about grep, thoughts about telling time on the Moon, and what does Canada have against the poor Flipper Zero, anyway?

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