Know Audio: Amplifier Nuts And Bolts

As we’ve followed a trail through Hi-Fi and audio systems from the listener’s ear towards the music source, we’ve reached the amplifier. In our previous article we gave a first introduction to distortion and how some amplifier characteristics can influence it, and here we’ll continue along that path and look at the amplifier itself. What types of audio amplifier circuits will you encounter, and what are their relative merits and disadvantages?

A Few Amplifier Basics

Horowitz and Hill's Transistor Man
Horowitz and Hill’s Transistor Man

If you know anything about a transistor, it’s probably that it’s a three terminal device whose output pin forms part of a potential divider whose state is dependent on what is presented to its input pin. The Art of Electronics had it as a cartoon of a man standing inside a bipolar transistor and adjusting a variable resistor between collector and emitter while watching an ammeter on the base.

Properly biased in its conducting range, a transistor can behave as a linear device, in which the potential divider voltage moves in response to the input in a linear relationship, and thus the voltage on the output is an amplified version of the voltage on the output. This is the simplest of transistor amplifiers, and because different types of amplifier are referred to by lettered classes, it’s known as a class A amplifier. Continue reading “Know Audio: Amplifier Nuts And Bolts”

Redefine Robots Is The Newest Hackaday Prize Challenge

Roboticists and automation enthusiasts, start your engines. This 2021 Hackaday Prize challenge is made just for you! It’s the Redefine Robots challenge and it calls for a softer, more utopian side of what tomorrow’s automated future can be.

The promise of robots has always been one of making our lives better. But so far we still don’t have a robot assistant sitting next to us ready to lend a hand. That’s where you come in! Whether it’s a physical, nuts-and-bots robot or a 1’s and 0’s software bot, create something that people can see and interact with in their day-to-day lives in ways that make sense and make us feel good about where technology is going.

We make fun of the robot that’s been brought into the world to pass the butter, but honestly if that’s something someone needs help with, isn’t a robot a pretty good solution? That’s what [Michael Roybal] thought way back during the 2016 Hackaday Prize when he designed Zizzy the robot to zip around a tabletop, assisting people with limited mobility.

In the same year, [Mike Rigsby] was working on a little bot whose purpose was to wander around interacting with people. A robot companion (dare we say pet?) is one way to keep up interactivity for people spending long periods of time alone. Along the same lines is the EMOJO chatbot already entered in this year’s contest that seeks to deliver a digital companion onscreen.

Assistive robots aren’t the only ones to shine here. Consider some labor savers, like pick-and-place robots that help you build electronics. Does that reinvent robots? Maybe, maybe not, but getting a 3D printer to do your solder for you sure does. Think of how revolutionary robot vacuums were for people who own both hardwood floors and cats. Those bots are around humans all the time and seem normal now. What’s next automation to get this introduction into everyday life?

Ten finalists from this round will win $500 and be shuttled onto the final round judging in October for a chance at the $25,000 Hackaday Prize and four other top prizes. Start your project page on Hackaday.io and use the drop-down in the left sidebar to enter it into the 2021 Hackaday Prize.

Sad clown holding melted ice cream cone

Freezing Out Ice Cream Machine Competition

We always knew that McDonald’s soft serve (you can’t really call it ice cream) machines are known to be finicky. There’s even a website that tracks where the machines are broken and, apparently, it is usually about 10% or more of them at any given time. But when we saw a news article about a judge issuing a restraining order, we knew there must be more to the story. Turns out, these $18,000 soft serve machines are in the heart of something we are very interested in: when do you own your own technology?

Cold Tech

There are apparently 13,000 or so of these machines and they are supposedly high-tech marvels, able to produce soft serve and milkshakes at the same time. However, they are also high maintenance. Cleaning the machine every two weeks (try not to think about that) involves a complete teardown. Worse, if anything breaks, you need a factory-authorized service person.

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Hackaday Links: August 22, 2021

It’s usually pretty hard to miss when Boston Dynamics drops a new video of one or more of their robots doing something flashy. But in case you’ve been under a rock the last few days, you might want to check out the Atlas parkour video. We last saw a pair of Atlas robots busting some dance moves with a few other Boston Dynamics robots, and while that was an incredible demonstration of the level of control they’ve engineered, they really were just playing back a series of preprogrammed moves. The obstacle course demo, though, seems like something different. There’s a good overview of the demo in IEEE Spectrum, where they point out that this is the first time we’ve seen Atlas show off using all four limbs at once for coordinated motion — that sweet vault over the fence. And really, it’s hard not to watch such human-like moves and not think that it’s just somebody in a robot suit. Even the stumbles feel human. What’s even more fun, though, is the behind-the-scenes look at Atlas. Especially for the face-plants and fails.

August 19 was the 100th anniversary of the birth of Gene Roddenberry, the creator of Star Trek. In the process of just trying to build a fictional universe to tell some interesting stories and make a little money, he managed to spawn not only an enduring science-fiction franchise but also to inspire generations of future scientists and engineers. The number of things that Star Trek writers invented to move their stories along that later showed up as actual products is astonishing, as are the weird coincidences like placing the fictional planet Vulcan in orbit around star 40 Eridani, only to find out that there’s actually a potentially habitable exoplanet circling that star. As a salute to Roddenberry, the Deep Space Network was used last week to send a message to 40 Eridani. One of the big dishes at the Goldstone DSN site in California blasted the 20-kW signal out on Thursday, starting it on its 16.5-year journey to the stars. We looked for details on what was sent, but the only description was that it contained a 1976 recording by the Great Bird of the Galaxy himself. Whatever it was, it’ll take at least 33 years to see if we get a response. Mark your calendars.

I’ve been doing a lot of work on cars lately, a task made considerably more approachable by the fact that the newest vehicle in the family fleet is from 2004. I find working on cars very satisfying, and I’m dreading the day when we’re forced to replace one of our old-timers with something more modern and less amenable to driveway repairs. That said, there’s also a lot to like about newer vehicles, particularly electric vehicles. It would be nice to have a way to move away from ICE vehicles while still being able to work on your ride. But if Ford’s tease this week of an EV crate motor comes to pass, it just might be the best of both worlds. The motor, bearing the unfortunate moniker “Eluminator” — just can’t resist putting that “E” in there, can they? — is supposed to be a drop-in replacement for an internal combustion engine, suitable for a “restomod” project. These car builds aim to make a car look as vintage as possible, but radically change the guts to add functionality — think a Raspberry Pi running a Spotify client that’s stuffed into a vintage Atwater Kent cathedral radio. We like the idea of electrifying an old car, but it seems to us that a crate motor is only part of the answer. Is there such thing as a crate battery?

And finally, there was an interesting article detailing a new approach to repairing ruptured eardrums using 3D printing. The tympanic membrane is a thin, delicate sheet of tissue that is easily punctured, whether by blunt-force trauma, infections, or even by loud sounds like gunshots or explosions. Hearing is compromised when an eardrum is damaged, and the hole can serve as a route for pathogenic microorganisms to get into the inner ear. Fixing the hole usually requires a graft from the patient’s own tissues, often sourced from the little dongle covering the ear canal. But this tissue isn’t nearly as thin as the natural eardrum, and while hearing can be restored, it’s often muddy and muffled. The new technique is to 3D-print a custom graft for the patient, using a special polymer and printer. The artificial membrane mimics the structure of the natural tympanic membrane and restores more natural hearing immediately. It also serves as a scaffold for the body to fill in with natural cells, hopefully returning natural function as the 3D-printed part is absorbed. It’s interesting work, and the video in the linked article is pretty fascinating too.

Keep Scraps Around

When I’m building something, I like to have a decent-sized scrap pile on hand. Because when I’ve got to test something out — does this glue adhere to this fabric, how much force will this hold if I tap it and put a screw in, will it snap if reinforced with carbon fiber and epoxy — it’s nice to have some of the material in question on hand just for experimentation. So I pull a chunk out of the scrap pile!

But scrap piles can’t expand forever, and we all know that “too much of a good thing” is a thing, right? Scrap piles require constant pruning. You don’t really need more than a few aluminum extrusion cutoffs, so when you start building up excess inventory, it’s time to scrap it. I mean, throw it away.

A corollary of this, that I’ve only recently started to appreciate, is that if I limit the number of materials that I’m working with, it’s a lot more manageable to keep the scrap pile(s) under control. It’s simple math. If I’m working with twenty different materials, that’s twenty different heaps of scrap. But if I can get by with one weight of fiberglass for everything, that one pile of scraps can do double or triple duty. There is also the added benefit that I already know how the material works, and maybe even have old test samples on hand.

Indeed, I’m such a scrapaholic that it’s almost painful to start working with a new material and not have a scrap pile built up yet. I’m always loathe to cut into a nice square piece of stock just to test something out. But this too is part of the Great Circle of Life. By not testing things out beforehand, I’m almost guaranteed to screw up and create scrap out of what I had hoped was going to be a finished piece. See? No problem! Next version.

What do you think? Are scrap, offcuts, and their close cousins — test pieces and samples — worth keeping around in your shop? Do you have a disciplined approach, or do you just throw them in the corner? Purge per project, or only when the mountain of XPS foam gets as high as your head?

Racks of ASIC mining hardware

Bitcoin In For Bumpy Ride As China Crackdown Shakes Things Up

Bitcoin. The magical internet money is often derided as “worthless” and “made up” by those who forget that all currencies only have value because we believe in them. Perhaps the world’s strongest currency not backed up by guns and ammo, Bitcoin nonetheless remains a controversial invention, as do the many cryptocurrencies that followed in its wake.

Recently, the Chinese government has cracked down on operations within the country. With China hosting the world’s largest fraction of Bitcoin mining capability, it’s sent shockwaves through the network and had a huge effect in a multitude of ways. Here’s what’s going down.

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Hackaday Podcast 132: Laser Disco Ball, Moore’s Law In Your Garage, Cheap Cyborg Glasses, And A Mouse That Detects Elephants

Hackaday editors Elliot Williams and Mike Szczys debate the great mysteries of the hacking universe. On tap this week is news that Sam Zeloof has refined his home lab chip fabrication process and it’s incredible! We see a clever seismometer built from plastic pipe, a laser, and a computer mouse. There’s a 3D printed fabric that turns into a hard shell using the same principles as jamming grippers. And we love the idea of high-powered lasers being able to safely direct lighting to where you want it.

Take a look at the links below if you want to follow along, and as always, tell us what you think about this episode in the comments!

Direct download (60 MB or so.)

Continue reading “Hackaday Podcast 132: Laser Disco Ball, Moore’s Law In Your Garage, Cheap Cyborg Glasses, And A Mouse That Detects Elephants”