All The Stuff You Wished You Knew About Fourier Transforms But Were Afraid To Ask

The Fourier transform underpins so much of our technological lives, in most cases probably without our realising it. The ability to mathematically split a waveform into its frequency components and vice versa underpins much of the field of digital signal processing, and DSP has become an essential part of many electronic devices we take for granted.

But while most of us will know what a Fourier transform is, fewer of us will know anything of how one works. They are a function called from a library rather than performed in themselves. Even when they are taught in schools or university courses they remain something that not all students “get”, and woe betide you if (as your scribe did) you have a sub-par maths lecturer.

The video below the break then is very much worth a look if Fourier transforms are a bit of a mystery to you. In it [Grant Sanderson] explains them through a series of simple graphical examples in a style that perhaps may chalk-and-talk mathematics teachers should emulate. You may still only use Foruier transforms through a library, but after watching this video perhaps some of their mysteries will be revealed.

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Celebrating the Olympics With Flaming Windmills

Like many of us, [Gustav Evertsson] was looking for an excuse to set stuff on fire and spin it around really fast to see what would happen. Luckily for him (and us) the Winter Olympics have started, which ended up being the perfect guise for this particular experiment. With some motors from eBay and some flaming steel wool, he created a particularly terrifying version of the Olympic’s iconic linked rings logo. Even if you won’t be tuning in for the commercials Winter Games, you should at least set aside 6 minutes to watch this build video.

The beginning of the build starts with some mounting brackets getting designed in Fusion 360, and you would be forgiven if you thought some 3D printed parts were coming up next. But [Gustav] actually loads the design up on a Carbide 3D CNC and cuts them out of wood.

A metal hub is attached to each bracket, and then the two pieces are screwed onto a length of thin wood. This assembly is then mounted up to the spindle of a geared motor rated for 300 RPM. The end result looks like a large flat airplane propeller. Five of these “propellers” are created, one for each ring of the Olympic’s logo.

Once the sun sets, [Gustav] takes his collection of spinners outside and lines them up like windmills. At the end of each arm is a small ball of fine-grade steel wool, which will emit sparks for a few seconds when lighted. All you’ve got to do is get the 10 pieces of steel wool alight at the same time, spin up the motors, and let persistence of vision do the rest. If you can manage the timing, you’ll be treated with a spinning and sparking version of the Olympic rings that wouldn’t look out of place in a new Mad Max movie.

Generally speaking, we don’t see much overlap between the hacker community and the Olympics. You’d have to go all the way back to 2012 to find another project celebrating this particular display of athleticism. We would strongly caution you not to combine both of these Olympic hacks at the same time, incidentally.

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Always Misplacing Your Keys? You Can Fix That With Some Logic Chips

Every time he came home, it was the same thing. As soon as he crossed the threshold, his keys just disappeared. There was no other logical explanation for it. And whenever it was time to leave again, he had to turn the house upside down to find them.

One day, [out-of-the-box] decided he’d had enough and built a door-activated alarm system out of stuff he had on hand—a decade counter, a cheapo reed switch-based door alarm, and some transistors. When the door is closed, the decade counter’s output is set to light up a green LED. When he comes home and opens the door, the reed switch closes, triggering the decade counter to shift its output to the next pin. The red LED comes on, and NPN transistor grounds the piezo, sounding the alarm. The only way to stop it is by inserting a shorted 1/4″ phone plug conveniently attached to his key ring into a jack on the circuit board until he hears that satisfying click of safe key-ping.

For those times when immediately plugging the keys into the wall isn’t feasible, or if his keys should disappear before he has the chance, there’s a momentary on the board that will stop the symphony of robotic cicadas blasting out from the piezo. It’s also good for family members who don’t want to play along or haven’t yet earned their 1/4″ plug.

Be sure to check out the build video after the break, which is just through that door there. And keep an eye on your keys, eh? Hackaday is not responsible for lost or stolen personal articles. Should you lose them, we can only suggest making a new car key from the spare and printing replacements for any standard keys.

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Careful Testing Reveals USB Cable Duds

What’s worse than powering up your latest build for the first time only to have absolutely nothing happen? OK, maybe it’s not as bad as releasing the Magic Smoke, but it’s still pretty bewildering to have none of your blinky lights blink like they’re supposed to.

What you do at that point is largely a matter of your troubleshooting style, and when [Scott M. Baker]’s Raspberry Pi jukebox build failed to chooch, he returned to first principles and checked the power cable. That turned out to be the culprit, but instead of giving up there, he did a thorough series of load tests on multiple USB cables to see which ones were suspect, with interesting results.

[Scott] originally used a cable with a USB-A on one end and a 3.5-mm barrel plug on the other with a switch in between, under the assumption that the plug on the Pi end would be more robust, as well as to have a power switch for the jukebox. Testing that cable using an adjustable DC load would prove that the cable was unfit for Pi duty, dropping the voltage to under 2 volts at a measly 500-mA load. Other cables proved much better under load, even those with USB mini jacks and even one with a 5.5-mm barrel. But the larger barrel-plug cable also proved to be a stinker when it was paired with an inline switch. In the video below, [Scott] walks through not only the testing process, but also gives a quick tour of his homebrew DC load.

The lesson is clear: not all USB cables are created equal, so caveat hacker. And if you’ve got a yen to check the cables in your junk bin like [Scott] did, this full-featured smart DC load might be just the thing.

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Twitter Celebration of Scientist Hacks For Lab And Field

If you like reading about scientists creatively using household objects for their work, you will enjoy browsing Twitter hashtag #reviewforscience where scientists are sharing stories of repurposing everyday things for their lab and field.

Research papers focus on the scientific hypothesis and the results of testing it. It is very common for such papers to leave out details of tools and techniques as irrelevant. (A solid scientific conclusion should be reproducible no matter what tools and techniques are used.) This sadly meant much of scientists’ ingenuity never see light.

We can thank Amazon user [John Birch] for this event. His son wished to study how ants from different colonies interact. In order to observe how these groups of ants react to each other while still keeping the populations separate, he wanted to keep one group of ants inside a tea strainer. He posted this technique as a review on the tea strainer’s Amazon product page, where it caught the attention of @RobynJWomack and started spreading, taking off when @DaniRabaiotti suggested the tag #reviewforscience.

Sadly, it appears our original scientist (who posted under his dad’s Amazon account) did not succeed with the tea strainer technique. But he has succeeded in drawing attention to creativity in science worldwide, as well as making his dad internet famous.

We love lab hacks here. For scientists who wish there was a place to document their creative lab hacks, might we suggest Hackaday.io?

[via Washington Post]

What Is This, A Controller For Ants?!

What’s the smallest controller you’ve ever used? [BitBuilt] forum user [Madmorda] picked up a cool little GameCube controller keychain with semi-working buttons at her local GameStop. As makers are wont to do, she figured she could turn it into a working controller and — well — the rest is history.

This miniaturized controller’s original buttons were essentially one piece of plastic and all the buttons would depress at once — same goes for the D-pad. Likewise, the original joystick and C-stick lacked springs and wouldn’t return to a neutral position after fidgeting with them. To get the ball rolling, [Madmorda] picked up a GC+ board — a custom GameCube controller board — just small enough to fit this project, eleven hard tact switches for the various buttons, and two squishy tact switches to replicate the original controller’s L and R button semi-analog, semi-digital functionality.

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Quick and Dirty Driver Tips for Surplus VFDs

Sometimes it seems like eBay is the world’s junk bin, and we mean that in the best possible way. The variety of parts available for a pittance boggles the mind sometimes, especially when the parts were once ordered in massive quantities but have since gone obsolete. The urge to order parts like these in bulk can be overwhelming, and sooner or later, you’ll find yourself with a fistful of old stuff but no idea how to put it to use.

Case in point: the box of Russian surplus seven-segment vacuum fluorescent displays (VFDs) that [w_k_fay] had to figure out how to use. The result is a tutorial on quick and dirty VFD drivers that looks pretty handy. [w_k_fay] takes pains to point out that these are practical tips for putting surplus VFDs to work, as opposed to engineered solutions. He starts with tips on characterizing your surplus tubes in case you don’t have a pinout. A 1.5 V battery will suffice for the hot cathode, while a 9 V battery will turn on the segments. The VFDs can be treated much like a common cathode LED display, and a simple circuit driving the tube with a 4026 decade counter can be seen below. He also covers the challenges of driving VFDs from microcontrollers, and promises a full build of a frequency counter wherein the mysteries of multiplexing will be addressed.

Sounds like it’s time to stock up on those surplus VFDs and put them to work. For inspiration, take a look at this minimalist VFD clock, or perhaps mix VFDs with Nixies to satisfy your urge for all things glowy.

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