The Physics Lesson I Keep Re-Learning

December 2, 2023 by Elliot Williams 69 Comments

One of the most broadly applicable ideas I’ve ever encountered is the concept of impedance matching. If you’re into radio frequency electronics, you’re probably thinking that I mean getting all your circuit elements working to a common characteristic resistance for maximum power transfer. (If you’re not, you’re probably wondering what that jumble of words even means. Fear not!)

But I mean impedance matching in the larger sense. Think about driving a stick-shift automobile. In low gear, the engine has a lot of torque on the wheels, but it can’t spin them all that fast. In high, the wheels turn fastest, but there’s not enough torque to get you started from a standstill. Sometimes you need more force and less motion, other times more motion and less force. The gearbox lets you match the motor’s power to the resistance – the impedance – it’s trying to overcome.

Or think about a cello. The strings are tight, and vibrate with quite a bit of force, but they don’t move all that much. Air, which is destined to carry the sound to your ear, doesn’t take much force to move, and the cello would play louder if it moved more of it. So the bridge conveys the small, but strong, vibrations of the strings and pushes against the top of the resonant box that makes up the body of the instrument. This in turn pushes a lot of air, but not very hard. This is also why speakers have cones, and also why your ear has that crazy stirrup mechanism. Indeed, counting the number of impedance matches between Yo Yo Ma and your brain, I come up with four or five, including electrical matches in the pre-amp.

I mention this because I recently ran into a mismatch. Fans blow air either hard or in large volume. If you pick a fan that’s designed for volume, and put it in a pressure application, it’s like trying to start driving in fifth gear. It stalled, and almost no air got pushed up through the beans in my new “improved” coffee roaster, meaning I had to rebuild it with the old fan, and quick before the next cup was due.

I ran into this mismatch even though I knew there was a possible impedance issue there. I simply don’t have a good intuitive feel how much pressure I needed to push the beans around – the impedance in question – and I bought the wrong fan. But still, knowing that there is a trade-off is a good start. I hope this helps you avoid walking in my footsteps!

Blinded With Science

August 12, 2023 by Elliot Williams 62 Comments

So the room-temperature superconductor was a super disappointment, but even though the claims didn’t stand up in the end, the even better news is that real science was done. A paper making extraordinary claims came out, the procedure to make LK-99 was followed in multiple labs around the world, and then it was tested. It didn’t turn out to conduct particularly well at all. After a couple weeks of global superconductor frenzy, everything is back to normal again.

What the heck happened? First of all, the paper itself made extravagant claims about a holy-grail kind of material. There was a very tantalizing image of a black pellet floating in mid air, which certainly seems like magic, even though it’s probably only run-of-the-mill ferromagnetism in the end. But it made for a great photo-op in a news-starved August, and the then-still-Twitterverse took to it by storm. And then the news outlets piled on the hype fest.

If you’re feeling duped by the whole turn of events, you’re not alone. But the warning signs were there from the beginning, if you took the time to look. For me, it was the closing line of the paper: “We believe that our new development will be a brand-new historical event that opens a new era for humankind.”

That’s not the kind of healthy skepticism and cautious conclusion that real science runs best on. Reading the paper, I had almost no understanding of the underlying materials science, but I knew enough about human nature to suspect that the authors had rushed the paper out the door without sufficient scrutiny.

How can we keep from being fooled again? Carl Sagan’s maxim that “extraordinary claims require extraordinary evidence” is a good start. To that, I would add that science moves slowly, and that extraordinary evidence can only accumulate over time. So when you see hype science, simply wait to draw any conclusions. If it is the dawn of a new era, you’ll have a lot of time to figure out what room-temperature superconductivity means to you in the rosy future. And if it’s just a flash in the pan, you won’t have gotten your hopes up.

Brainstorming

November 19, 2022 by Elliot Williams 5 Comments

One of the best things about hanging out with other hackers is the freewheeling brainstorming sessions that tend to occur. Case in point: I was at the Electronica trade fair and ended up hanging out with [Stephen Hawes] and [Lucian Chapar], two of the folks behind the LumenPnP open-source pick and place machine that we’ve covered a fair number of times in the past.

Among many cool features, it has a camera mounted on the parts-moving head to find the fiducial markings on the PCB. But of course, this mean a camera mounted to an almost general purpose two-axis gantry, and that sent the geeks’ minds spinning. [Stephen] was talking about how easy it would be to turn into a photo-stitching macrophotography rig, which could yield amazingly high resolution photos.

Meanwhile [Lucian] and I were thinking about how similar this gantry was to a 3D printer, and [Lucian] asked why 3D printers don’t come with cameras mounted on the hot ends. He’d even shopped this idea around at the East Coast Reprap Festival and gotten some people excited about it.

So here’s the idea: computer vision near extruder gives you real-time process control. You could use it to home the nozzle in Z. You could use it to tell when the filament has run out, or the steppers have skipped steps. If you had it really refined, you could use it to compensate other printing defects. In short, it would be a simple hardware addition that would open up a universe of computer-vision software improvements, and best of all, it’s easy enough for the home gamer to do – you’d probably only need a 3D printer.

Now I’ve shared the brainstorm with you. Hope it inspires some DIY 3DP innovation, or at least encourages you to brainstorm along below.

The Quiet Before The Storm?

August 27, 2022 by Elliot Williams 82 Comments

My wife and I are reading a book about physics in the early 1900s. It’s half history of science and half biography of some of the most famous physicists, and it’s good fun. But it got me thinking about the state of physics 120 years ago.

What we’d now call classical mechanics was fully settled for quite a while, and even the mysterious electricity and magnetism had been recently put to rest by Maxwell and Heaviside. It seemed like there was nothing left to explain for a while. And then all the doors broke wide open.

As much as I personally like Einstein’s relativity work, I’d say the most revolutionary change in perspective, and driver of the most research in the intervening century, was quantum mechanics. And how did it all start? In the strangest of ways – with Niels Bohr worrying about why hydrogen and helium gasses gave off particular colors when ionized, which lead to his model of the atom and the idea of energy in quantum packets. Or maybe it was De Broglie’s idea that electrons could behave like waves or magnets, from slit and cathode-ray experiments respectively, that lead to Heisenberg’s uncertainty principle.

Either way, the birth of the strangest and most profound physics revolution – quantum mechanics – came from answering some ridiculously simple and straightforward questions. Why does helium emit pink, and how do TVs work? (I know, they didn’t have TVs yet…) Nobody looking at these phenomena, apart or together, could have thought that answering them would have required a complete re-thinking of how we think about reality. And yet it did.

I can’t help but wonder if there are, in addition to the multi-bazillion dollar projects like the Large Hadron Collider or the James Webb Space Telescope, some simpler phenomena out there that we should be asking “why?” about. Are we in a similar quiet before the storm? Or is it really true that the way to keep pushing back the boundaries of our ignorance is through these mega-projects?

Ask Hackaday: Is Bigger (E-mail) Better?

June 13, 2022 by Al Williams 30 Comments

While pundits routinely predict the end of e-mail, we still get a ton of it and we bet you do too. E-mail has been around for a very long time and back in the day, it was pretty high-tech to be able to shoot off a note asking everyone where they wanted to go to lunch. What we had on our computers back then was a lot different, too. Consider that the first e-mail over ARPANET was in 1971. Back then some people had hardcopy terminals. Graphics were unusual and your main storage was probably a fraction of the smallest flash drive you currently have on your desk. No one was sending photographs, videos, or giant PDF files.

Today, things are different. Our computers have gigabytes of RAM and terabytes of storage. We produce and consume richly formatted documents, photographs at high resolutions, and even video. Naturally, we want to share those files with others, yet e-mail has turned up woefully short. Sure, some systems will offer to stash your large file in the cloud and send a link, but e-mailing a multi-megabyte video to your friend across town is more likely to simply fail. Why?

Continue reading “Ask Hackaday: Is Bigger (E-mail) Better?” →

The Virtue Of Wires In The Age Of Wireless

April 9, 2022 by Elliot Williams 47 Comments

We ran an article this week about RS-485, a noise resistant differential serial multidrop bus architecture. (Tell me where else you’re going to read articles like that!) I’ve had my fun with RS-485 in the past, and reading this piece reminded me of those days.

You see, RS-485 lets you connect a whole slew of devices up to a single bundle of Cat5 cable, and if you combine it with the Modbus protocol, you can have them work together in a network. Dedicate a couple of those Cat5 lines to power, and it’s the perfect recipe for a home, or hackerspace, small-device network — the kind of things that you, and I, would do with WiFi and an ESP8266 today.

Wired is more reliable, has fewer moving parts, and can solve the “how do I get power to these things” problem. It’s intrinsically simpler: no radios, just serial data running as voltage over wires. But nobody likes running cable, and there’s just so much more demo code out there for an ESP solution. There’s an undeniable ease of development and cross-device compatibility with WiFi. Your devices can speak directly to a computer, or to the whole Internet. And that’s been the death of wired.

Still, some part of me admires the purpose-built simplicity and the bombproof nature of the wired bus. It feels somehow retro, but maybe I’ll break out some old Cat5 and run it around the office just for old times’ sake.

Confessions Of A Crimpoholic

April 4, 2022 by Dan Maloney 80 Comments

Hi, my name is Dan and I’m a crimpoholic.

Honestly, I didn’t know I was a serial abuser of crimping tools until this weekend. I’ve been working on a small solar power system, and on Saturday I found myself struggling to get the BMS installed on the battery. I bought a Bluetooth dongle to connect the BMS to a smartphone app for checking the individual cells of the battery. I assumed it would just plug right into the UART port on the BMS, but alas — different connectors. So off I went to my bench, looking for a sensible way to make the connection.

My first thought was to simply log the connector off the dongle and solder the leads to the traces on the PCB right below the UART port. But then I saw that the pins in the port looked like 0.1″ pitch, so I rummaged through my stash to see what I could find. To my surprise, I had not only a kit of 0.1″ female crimps and housings, but I also had the crimping tool for them! I had no memory of making the purchase, but I thanked my lucky stars that I did, and got on with the job.

Continue reading “Confessions Of A Crimpoholic” →