Misc Hacks

4032 Articles

The 7805 Is Dead! Long Live The 7805!

September 5, 2022 by 70 Comments

The 78XX series of regulators are very handy to use. If you need, say, a 5V regulator, you grab a 7805, add a capacitor for stability, and send in enough voltage for the regulator to work with. Cheap and easy. However, the part is not without its faults.

A stock 7805 can’t convert 5.1V to 5V. You need to have a good bit more voltage coming in. But the more voltage you put in, the more the part is going to dump out as heat. So running from 9V is going to be cooler than running from 24V. All that heat isn’t very energy efficient on batteries, either. [Stefan] wanted to do better, so he made a drop-in replacement for these venerable regulators some time ago. But he’s recently made the board layouts available so you can build your own replacement, too.

The device accepts 4.5 to 16V, and you can select the output voltage using two resistors. You can draw up to 2A out of the regulator, which is more than you can say for a stock 7805.

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Hackaday Prize 2022: Drying Clothes With Ultrasound

September 4, 2022 by 29 Comments

Clothes dryers are great, and a key part of modern life, but they do use a lot of energy. [Mike Rigsby] decided to see if there was a more efficient method of drying clothes that could compete with resistive heating for efficiency. Thus, he started work on an ultrasonic clothes dryer.

In early testing, he found ultrasonic transducers could indeed blast droplets of moisture away from fabric, effectively drying it. However, unlike heat, the ultrasonic field doesn’t effectively permeate through a pile of clothes, nor can it readily be used with a spinning drum to dry many garments at once.

[Mike]’s current experiments are centered around using a basket-type system, with a bed of ultrasonic transducers at the bottom. The idea is that the basket will shake back and forth, agitating the load of clothing and allowing the different garments to effectively contact the transducers. It’s still a work in progress, but it’s an interesting approach to the problem. We’d love to see a comparison of the energy use of a full-scale build versus a regular dryer.

We’ve heard of the ultrasonic drying concept before, too, with the Department of Energy researching the matter. It could just be that we’ll all be using ultrasonic dryers in decades to come!

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Hackaday Prize 2022: Treadmill Becomes Human-Powered Generator

September 3, 2022 by 11 Comments

Running on a treadmill is a great way to workout, but what if the effort you put in could be put to use? This treadmill generator from [Amitabh Shrivastava] does just that.

The build starts with a regular old treadmill, which has a motor inside typically used to power the tread. Instead, the motor’s control electronics were removed, and it was repurposed to work as a generator. The output from the treadmill’s DC motor was fed directly to a DC-DC converter. This was then fed to an inverter that generates 120 V AC, which can power appliances that use up to 20-25W based on [tinkrmind’s] running performance.

It’s a fun way to generate power during a workout. If you don’t want your treadmill’s monitor to die in the middle of a Friends rerun, you’ll have to dig deep on those long runs. We’ve seen similar builds before too, with exercise bikes being a popular method of generating electricity. In fact, that’s [Amitabh]’s next project! Video after the break.

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Fixing A Hot Shop, With Science

September 2, 2022 by 42 Comments

We know that pretty much everybody in the Northern hemisphere has had a hellish summer, and there’s little room for sympathy when someone busts out with, “Oh yeah? You think THAT’s hot? Well, lemme tell you…” But you’ve got to pity someone who lives in north Texas and has a steel Quonset hut for a shop. That’s got to be just stupidly hot.

But stupid hot can be solved — or at least mitigated — with a little smarts, which is what [Wesley Treat] brought to bear with this cleverly designed shop door heat shield. When it pushes past 42°C — sorry, that sounds nowhere near as apocalyptic as 108°F — the south-facing roll-up door of his shop becomes a giant frying pan, radiating heat into his shop that the air conditioner has trouble handling. His idea was to block that radiant heat with a folding barrier, but to make sure it would be worth the effort, he mocked up a few potential designs and took measurements of the performance of each. His experiments showed him that a layer of extruded polystyrene (XPS) foam insulation covered with reflective Mylar did better than just the foam or Mylar alone.

The finished heat shield is an enormous tri-fold plywood beast that snugs up against the door when things get toasty in the shop. There’s a huge difference in temperature between the metal door and the inside surface of the shield, which will hopefully keep the shop more comfortable. We imagine that the air between the door and the shield will still heat up, and convection could still distribute all that hot air into the shop. But at least he’s giving the AC a fighting chance.

In addition to great shop tips like this and his custom storage bins, [Wesley] is a talented signmaker. He’s pretty funny too — or maybe that’s just the heat talking.

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Magic Eye Tubes Go Solid State With This Plug-In Replacement

August 29, 2022 by 35 Comments

Perhaps nothing added quite so much to the charm of vacuum tube circuits from back in the heyday of the vacuum tube as did the “Magic Eye” indicating tube. With the ghostly green glow of its circular face, magic eyes stood in for more expensive moving-coil meters for things like tuning indicators and VU meters. And while they may be getting hard to come by today, fear not — this solid-state replacement for the magic eye tube is ready to stand in for your restoration projects.

To pull off this clever build, [Gord Rabjohn] started with original 6E5 and 6U5 magic eye tubes, presumably ones that either no longer worked or had become too weak to see. The glass envelopes of the cathode-ray tubes were carefully cut from the sockets, and the guts of the tubes were discarded to make room for the replacement circuit, which lives on two PCBs. A rectangular control board holds an LM3915 bar graph LED driver chip, while a round display PCB holds 120 surface-mount green LEDs. The circular display board is mounted at the top of the control board and perpendicular to it, with a diffuser mounted above the LEDs. Everything is stuffed back into the original glass envelope and socket, making this a plug-in replacement for the tube.

The effect is quite convincing, as shown in the video below. True, you can see some evidence of the individual LEDs even with the diffuser, but honestly this just makes the display look more like the iris of an eye. We really like the look of this and we appreciate the work [Gord] put into it, especially the documentation. For a little more on how the tubes worked, check out [Al Williams]’ article.

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Visual Mandela Effect: You Don’t Know Iconic Images As Well As You Think

August 29, 2022 by 63 Comments

Pop quiz, hotshot: does the guy on the Monopoly box (standard edition) wear a monocle? Next question: does the Fruit of the Loom logo involve a cornucopia? And finally, does Pikachu have a black-tipped tail? If you answered yes to any of these, I am sad to say that you are wrong, wrong, wrong.

So, what’s the deal? These are all examples of the visual version of the Mandela effect (VME), which is named after the common misconception/mass false memory that anti-Apartheid activist Nelson Mandela died decades ago in prison, despite leading South Africa in the latter half of the ’90s and living until 2013. Many people even claim having seen TV coverage of his funeral, or say they learned about his death in school during Black History Month. The whole thing has VICE wondering whether CERN is causing these mass delusions somehow with the LHC.

The more attention VME gets, the more important it seems to be to study it and try to come to some conclusion. To that end, University of Chicago researchers Deepasri Prasad and Wilma A. Bainbridge submitted an interesting and quite readable study earlier this year purporting that the VME is ‘evidence for shared and specific false memories across people’. In the study, they conducted four experiments using crowd-sourced task completion services.

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A tennis racket and a tennis ball with a spinning motor inside

A Self-Spinning Tennis Ball To Surprise Your Opponent

August 25, 2022 by 6 Comments

In many ball sports like golf, football and tennis, controlling the ball’s spin is an important skill. Expert players can make golf balls curve around obstacles, launch footballs towards goal posts from impossible angles, or confuse their opponents by making a tennis ball bounce in a completely unexpected direction.

[Luis Marx], by his own admission, is not an expert tennis player at all, so when he found himself humiliated on the court by his roommate he set about finding a different way to win. In other words, to cheat. The basic idea was to make a tennis ball that would start spinning at the push of a button, rather than by skillful wielding of a racket: a spinning ball that flies through the air will follow a curved trajectory, so if you can make a ball spin at will, you can change its direction in mid-air.

Making a ball spin by itself is not as hard as it may sound. All you need is an electric motor that’s small enough to fit inside, along with a power source and some way to turn it on. When the motor inside the ball starts to spin, Newton’s third law ensures that the outside will spin in the opposite direction. [Luis] found a suitable DC motor and mounted it on a small custom-designed PCB along with an ESP8266 controller and powered it with a tiny lithium battery. A pushbutton mounted on his tennis racket operates the wireless interface to turn the motor on and off.

Although getting this setup to work wasn’t as easy as [Luis] had hoped, turning it into a ball that’s good enough to play tennis with was not straightforward either. [Luis] decided to 3D-print the outer shell using flexible filament in order to create something that would have the same amount of bounce as an ordinary rubber tennis ball. It took several rounds of trial and error with various types of filament to end up with something that worked, but the final result, as you can see in the video (in German, embedded below), was quite impressive.

Tests on the tennis court showed that [Luis] could now easily beat his roommate, although this was mostly due to the erratic bouncing caused by the ball’s spin rather than any aerodynamic effects. Still, the magic tennis ball achieved its objective and even survived several games without breaking. If you’re looking for a more brute-force approach to cheating at tennis, this 180 mph tennis ball trebuchet might come in handy.

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