Author: Dan Maloney

3368 Articles

Generating Stereo FM Signals, Thanks To Python

October 19, 2022 by 7 Comments

A casual understanding of how AM radio works is pretty easy to come by, and standard FM is only a little more complicated. Things can go off the tracks a bit with stereo FM, though — figuring out how they squeeze two separate audio tracks onto one radio signal is a bit of a head-scratcher. In that case, wrapping your head around the concept might be helped by mocking up a stereo FM signal with an arbitrary waveform generator and a little bit of Python.

Not that [Sebastian] of Baltic Lab was unfamiliar with multiplex FM theory, mind you. As he explains it, his goal was to generate a valid stereo FM signal with a different pure tone on each channel, 700 Hz on the left and 2,200 Hz on the right. Luckily, [Sebastian] has a nice AWG, the Siglent SDG1032X, which has an Ethernet connection that can be used to control it remotely along with PyVISA, a Python package for controlling instruments using the Virtual Instrument Software Architecture protocol.

The meat of this project, and what really helps drive home the concept of putting multiple audio signals onto an FM signal, lies in the Python code that generates the component parts. [Sebastian] does a great job explaining how he programatically generates the sum and difference signals along with the 19 kHz pilot tone, and puts them all together into one waveform. The output of the program is used to generate a series of values that are sent to the arbitrary waveform generator, which outputs the desired FM signal. Looking at the output on a spectrum analyzer, the two audio tones are clearly visible, as are the attenuated pilot tone and some other spikes a little further up.

Just add an antenna to the setup and you’d have the world’s dullest FM radio station — but at least it’d be in stereo. Or if you want to check out the origin story for FM radio, we’ve got something for that too.

Mining And Refining: Cobalt, The Unfortunately Necessary Metal

October 18, 2022 by 21 Comments

The story of humankind is largely a tale of conflict, often brought about by the uneven distribution of resources. For as long as we’ve been down out of the trees, and probably considerably before that too, our ancestors have been struggling to get what they need to survive, as often as not at the expense of another, more fortunate tribe. Food, water, land, it doesn’t matter; if They have it and We don’t, chances are good that there’s going to be a fight.

Few resources are as unevenly distributed across our planet as cobalt is. The metal makes up only a fraction of a percent of the Earth’s crust, and commercially significant concentrations are few and far between, enough so that those who have some often end up at odds with those who need it. And need it we do; what started in antiquity as mainly a rich blue pigment for glass and ceramics has become essential for important industrial alloys, high-power magnets, and the anodes of lithium batteries, among other uses.

Getting access to our limited supply of cobalt and refining it into a useful metal isn’t a trivial process, and unfortunately its outsized importance to technological society forces it into a geopolitical role that has done a lot to add to human misery. Luckily, market forces and new technology are making once-marginal sources viable, which just may help us get the cobalt we need without all the conflict.

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Lubrication Engineering Hack Chat

October 17, 2022 by 27 Comments

Join us on Wednesday, October 19 at noon Pacific for the Lubrication Engineering Hack Chat with Rafe Britton!

You know the old joke: if it moves when it shouldn’t, fix it with duct tape, and if it doesn’t move but it should, fix it with WD-40. For a lot of us, that’s about as far as our expertise on lubricants — and adhesives — goes. That’s a shame, because with hundreds of years of petrochemical engineering expertise behind us, not to mention millennia more of ad hoc experience with natural substances, just reaching for that trusty blue and yellow can for a spritz is perhaps a wasted opportunity. Sure, it’ll work — maybe — but is it really the right tool for the job?

Modern lubricants are extremely complex and highly engineered materials, often built atom by atom to perform a specific job under specific, often extremely challenging, conditions. Oils and greases are much more than just the slippery stuff that keeps our mechanical systems running, and while you might not need to know all the details of how they’re made to put them to use, a little inside information could go a long way in making sure your mechanism lasts.

join-hack-chatWe’ve invited Rafe Britton on the Hack Chat to talk about all aspects of lubrication engineering. With degrees in engineering and physics, Rafe runs Lubrication Expert and the Lubrication Explained channel on YouTube to help his clients figure out what they don’t know about lubrication, and how to put that knowledge to use in the real world. Be sure to bring your questions and concerns about lubrication, as well as your lubrication success stories and failures — especially the failures!

Our Hack Chats are live community events in the Hackaday.io Hack Chat group messaging. This week we’ll be sitting down on Wednesday, October 19 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: October 16, 2022

October 16, 2022 by 20 Comments

Be careful where your take your iPhone 14 or Apple Watch, because under the right circumstances, you might end up swatting yourself. At least that’s what seems to have happened to some owners when their device’s crash detection feature interpreted a roller coaster ride as a car crash, and dialed emergency services. Crash detection is apparently set up to make the call automatically when accelerometers detect the high g-forces that normally occur in a crash, but can also occur on a coaster ride — at least the good one. In at least one case, an ersatz call to 911 was accompanied by the screams of fellow coaster riders, as the service apparently opens the device’s microphone when a crash is detected.

Hilarity ensued, of course, as long as you weren’t someone with a legit emergency who experienced a delayed response because of this. We’d have sworn that having a system auto-dial 911 was strictly illegal for just this reason, but apparently not. We guess there are two lessons here: one, that Apple engineers really should have thought this through, and maybe need to get out into the real world once in a while; and two, that people will gladly fork over their hard-earned dollars for the privilege of going on a fun ride that’s indistinguishable from a car crash. Our own Lewin Day took a close look at the situation earlier this week if you’d like to read more on the subject.

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2022 Cyberdeck Contest: A Wrist-Worn Deck With A Hybrid Interface

October 16, 2022 by 4 Comments

You’d think that now that the 2022 Cyberdeck Contest is wrapped up, we’d stop writing about it. Sorry, but no — there were so many great entries that we just can’t help but keep focusing on them. And this wearable hybrid interface cyberdeck has a look we love so much that we can’t resist spotlighting it.

We wouldn’t go so far as to call the “hgDeck” a PipBoy, but [Igor Brkić]’s wrist-worn deck certainly bears some similarity with to the Fallout-famous terminal. In fact, the design for this one is based on his earlier hgTerm Raspberry Pi mini-laptop, which honestly would have made a great entry all by itself. But while the two version shares some similarities, the hgDeck puts a serious twist on the form factor. In the stowed configuration, the Pi Zero W puts the main display, a 3.5″ Waveshare TFT, to work using the resistive touchscreen interface. But with the flick of a finger, a motor flips the monitor up on a set of pantograph linkages, which exposes a compact Bluetooth keyboard. Another touch stows the screen and returns you to touchscreen-only operation.

There were a fair number of wrist-worn decks in the contest’s final results, and while this one didn’t win, [Igor]’s build has got to be one of the cooler designs we’ve seen, one that almost seems practical in the real world.

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To Turn An ATtiny817 Into A 150MHz Counter, First Throw Out The Spec Sheet

October 14, 2022 by 20 Comments

One generally reads a data sheet in one of two ways. The first is to take every spec at face value, figuring that the engineers have taken everything into account and presented each number as the absolute limit that will prevent the Magic Smoke from escaping. The other way is to throw out the data sheet and just try whatever you want, figuring that the engineers played it as safely as possible.

The latter case seems to have been the motivation behind pushing an ATtiny way, WAY beyond what the spec sheet says is possible. According to [SM6VFZ], the specs on the ATtiny817 show that the 12-bit timer/counter D (TCD) should be limited to a measly 32 MHz maximum frequency, above which one is supposed to employ the counter’s internal prescaler. But by using a 10-MHz precision frequency generator as an external clock, [SM6VFZ] found that inputs up to slightly above 151 MHz were countable with 1-Hz precision. Above that point, things started to drift, but that’s still pretty great performance from something cobbled together on an eval board in a decidedly suboptimal way.

We’d imagine this result could lead to some interesting projects, since the undocumented limit for this timer puts it well within range of multiple amateur radio allocations. Even if it doesn’t prove useful, that’s OK — just seeing how far things can be pushed is cool too. And it’s not like this is the first time we’ve caught [SM6VFZ] persuading an ATtiny to do unusual things, either.

Imagining A Dune-accurate Fremen Thumper

October 13, 2022 by 30 Comments

Never underestimate the power of fandom to obsess over the smallest details of its chosen canon. We say that with all due respect, of course, as some of the builds that result are really cool, like this working Fremen thumper from the Dune universe.

If you aren’t up to speed on [Frank Herbert]’s sci-fi epic, the Fremen are a warrior race that populates the sands of the desert planet Arrakis, which is inhabited by giant sandworms. The worms are attracted to vibrations, and thumpers are supposed to be mechanical devices set into the sand to lure worms. Thumpers are only vaguely described in the text, and have been imagined to varying degrees of success in the filmed versions of the story.

[Attoparsec] decided to take a stab at a working version, with the twist of making it plausible within what’s known about the Fremen in the stories. He settled on a pneumatic drive, which seems like something the Fremen would use. Using compressed CO2 cartridges, he discovered that it’s far easier to make a high-speed pneumatic vibrator than it is to make a piston move slowly up and down. Several iterations were needed to get to a mechanism capable of the more stately movements seen in any of the film versions of the story, and even then the thumping seems a bit fast for our liking. The triggering mechanism was very cool, though, and somewhat unexpected — [Herbert] describes “lighting the candle” to trigger a thumper, which led to the use of a thermal pressure relief valve and a fuse.

The video below goes over the design and build in some detail, as well as demonstrates the thumper in action with a clever cosplay bit. Hats off to [Attoparsec] for this dive down the fandom rabbit hole, maybe a faithful version of the “pain box” will be next up on the project list.

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