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In Praise Of The DT830, The Phenomenal Instrument You Probably Don’t Recognise For What It Is

September 24, 2020 by 133 Comments

If we had to make a guess at the single piece of electronic bench equipment owned by the highest proportion of Hackaday readers, it would not be a budget oscilloscope from Rigol, nor would it be a popular portable soldering iron like the TS100. Instead we’re guessing that it’s a multimeter, and not even the most accomplished one.

The DT830 is a genericised Chinese-manufactured 3.5 digit digital multimeter that can be had for an astonishingly low price. Less than a decent hamburger gets you an instantly recognisable plastic case with a chunky rotary range selector switch, and maybe a socket for some kind of transistor or component tester. Make sure that there is a 9 volt battery installed, plug in the pair of test leads, and you’re in business for almost any day-to-day electrical or electronic measurement. They’ve been available in one form or another for decades and have been the subject of innumerable give-aways and loss-leader offers, so it’s a reasonsble guess that you’ll have one somewhere. I have three as far as I know, they make great on-the-go instruments and have proved themselves surprisingly reliable for what they are. Continue reading “In Praise Of The DT830, The Phenomenal Instrument You Probably Don’t Recognise For What It Is” →

Dynamic Soaring: 545 MPH RC Planes Have No Motor

September 24, 2020 by 59 Comments

The fastest remote-controlled airplane flight ever recorded took place in 2018, with a top speed of 545 miles/hour. That’s 877 km/h, or Mach 0.77!

What was the limiting factor, preventing the pilot-and-designer Spencer Lisenby’s plane from going any faster? The airstream over parts of the wing hitting the sound barrier, and the resulting mini sonic booms wreaking havoc on the aerodynamics. What kind of supercharged jet motor can propel a model plane faster than its wings can carry it? Absolutely none; the fastest RC planes are, surprisingly, gliders.

Dynamic soaring (DS) was first harnessed to propel model planes sometime in the mid 1990s. Since then, an informal international competition among pilots has pushed the state of the art further and further, and in just 20 years the top measured speed has more than tripled. But dynamic soaring is anything but new. Indeed, it’s been possible ever since there has been wind and slopes on the earth. Albatrosses, the long-distance champs of the animal kingdom, have been “DSing” forever, and we’ve known about it for a century.

DS is the highest-tech frontier in model flight, and is full of interesting physical phenomena and engineering challenges. Until now, the planes have all been piloted remotely by people, but reaching new high speeds might require the fast reaction times of onboard silicon, in addition to a new generation of aircraft designs. The “free” speed boost that gliders can get from dynamic soaring could extend the range of unmanned aerial vehicles, when the conditions are right. In short, DS is at a turning point, and things are just about to get very interesting. It’s time you got to know dynamic soaring.

Continue reading “Dynamic Soaring: 545 MPH RC Planes Have No Motor” →

Community Testing Suggests Bias In Twitter’s Cropping Algorithm

September 23, 2020 by 77 Comments

With social media and online services are now huge parts of daily life to the point that our entire world is being shaped by algorithms. Arcane in their workings, they are responsible for the content we see and the adverts we’re shown. Just as importantly, they decide what is hidden from view as well.

Important: Much of this post discusses the performance of a live website algorithm. Some of the links in this post may not perform as reported if viewed at a later date. 

The initial Zoom problem that brought Twitter’s issues to light.

Recently, [Colin Madland] posted some screenshots of a Zoom meeting to Twitter, pointing out how Zoom’s background detection algorithm had improperly erased the head of a colleague with darker skin. In doing so, [Colin] noticed a strange effect — although the screenshot he submitted shows both of their faces, Twitter would always crop the image to show just his light-skinned face, no matter the image orientation. The Twitter community raced to explore the problem, and the fallout was swift.

Continue reading “Community Testing Suggests Bias In Twitter’s Cropping Algorithm” →

Hard Disk Drives Have Made Precision Engineering Commonplace

September 23, 2020 by 50 Comments

Modern-day hard disk drives (HDDs) hold the interesting juxtaposition of being simultaneously the pinnacle of mass-produced, high-precision mechanical engineering, as well as the most scorned storage technology. Despite being called derogatory names such as ‘spinning rust’, most of these drives manage a lifetime of spinning ultra-smooth magnetic storage platters only nanometers removed from the recording and reading heads whose read arms are twitching around using actuators that manage to position the head precisely above the correct microscopic magnetic trace within milliseconds.

Despite decade after decade of more and more of these magnetic traces being crammed on a single square millimeter of these platters, and the simple read and write heads being replaced every few years by more and more complicated ones, hard drive reliability has gone up. The second quarter report from storage company Backblaze on their HDDs shows that the annual failure rate has gone significantly down compared to last year.

The question is whether this means that HDDs stand to become only more reliable over time, and how upcoming technologies like MAMR and HAMR may affect these metrics over the coming decades.

Continue reading “Hard Disk Drives Have Made Precision Engineering Commonplace” →

Inputs Of Interest: BIGtrack Mouse Might Make You Squeal

September 22, 2020 by 20 Comments

You know me, I like to get my feet involved when I use my computer, which happens pretty much all day every day at this point. My cache of pedal inputs keeps growing like mushrooms in the darkness under my desk: every upper case letter in this post and dozens more have been capitalized with a shift pedal!

Naturally, I’ve thought about what it might be like to mouse with my toes. The more time I can spend with both hands on the keyboard, the better. I started sniffing around for foot-sized trackball candidates, thinking maybe I could just build one with regular mouse guts. Then I found a 15-year-old Golden Tee home edition console at a thrift store. It has a large ball and four buttons, so it seemed ripe for turning into a mouse as-is, or just stealing the ball to build my own. So far, that hasn’t happened, though I did solder a bunch of wires for testing out the controls. Continue reading “Inputs Of Interest: BIGtrack Mouse Might Make You Squeal” →

Axe Hacks: New Sounds For Your Electric Guitar Beginning From What Makes Them Tick

September 22, 2020 by 30 Comments

Creating music is a perfect hobby for anyone into hacking, and the amount of musical hacks and self-made instruments we come across here makes that supremely evident. It’s just a great match: you can either go full-on into engineering mode as music is in the end “just” applied physics, or simply ignore all of the theory and take an artistic approach by simply doing whatever feels right. The sweet spot is of course somewhere in between — a solid grasp of some music theory fundamentals won’t hurt, but too much overthinking eventually will.

The obvious choice to combine a favorite pastime like electronics or programming with creating music would be in the realm of electronic music, and as compelling as building synthesizers sounds, I’ll be going for the next best thing instead: the electric guitar. Despite its general popularity, the enormous potential that lies within the electric guitar is rarely fully utilized. Everyone seems to just focus on amp settings and effect pedals when looking for that special or unique sound, while the guitar itself is seen as this immutable object bestowed on us by the universe with all its predestined, magical characteristics. Toggle a pickup switch, and if we’re feeling extra perky, give that tone pot a little spin, that’s all there is to it.

The thing is, the guitar’s electrical setup — or wiring — in its stock form simply is as boring and generic as it can get. Sure, it’s a safe choice that does the job well enough, but there’s this entirely different world of tonal variety and individual controllability locked inside of it, and all it really takes is a screwdriver and soldering iron to release it. Plus, this might serve as an interesting application area to dive into simple analog electronics, so even if guitars aren’t your thing yet, maybe this will tickle your creativity bone. And if bass is more your thing, well, let me be ignorant and declare that a bass is just a longer guitar with thicker, lower-tuned strings, meaning everything that follows pretty much applies to bass as well, even if I talk about guitars.

However, in order to modify something, it helps to understand how it functions. So today, we’ll only focus on the basics of an electric guitar, i.e. what’s inside them and what defines and affects their tone. But don’t worry, once we have the fundamentals covered, we’ll be all settled to get to the juicy bits next time.

Continue reading “Axe Hacks: New Sounds For Your Electric Guitar Beginning From What Makes Them Tick” →

Linux Fu: Simple SSH File Sharing

September 21, 2020 by 28 Comments

If you have more than one Linux computer, you probably use ssh all the time. It is a great tool, but I’ve always found one thing about it strange. Despite having file transfer capabilities in the form of scp and sftp, there is no way to move a file back or forth between the local and remote hosts without starting a new program on the local machine or logging in from the remote machine back to the local machine.

That last bit is a real problem since you often access a server from behind a firewall or a NAT router with an ephemeral IP address, so it can’t reconnect to you anyway. It would be nice to hit the escape character, select a local or remote file, and teleport it across the  interface, all from inside a single ssh session.

I didn’t quite get to that goal, but I did get pretty close. I’ll show you a script that can automatically mount a remote directory on the local machine. You’ll need sshfs on the local machine, but no changes on the remote machine where you may not be able to install software. With a little more work, and if your client has an ssh server running, you can mount a local directory on the remote machine, too. You won’t need to worry about your IP address or port blocking. If you can log into the remote machine, you are good.

Combined, this got me me very close to my goal. I can be working in a shell on either side and have access to read or write files on the other side. I just have to set it up carefully. Continue reading “Linux Fu: Simple SSH File Sharing” →