spin

8 Articles

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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New Resin Printing Method Creates Objects In Seconds

June 1, 2022 by 20 Comments

For anyone looking to buy a 3D printer at home, the first major decision that needs to be made is whether to get a resin printer or a filament printer. Resin has the benefits of finer detail, but filament printers are typically able to produce stronger prints. Within those two main camps are various different types and sizes to choose from, but thanks to some researchers at Switzerland’s École polytechnique fédérale de Lausanne (EPFL) there’s a new type of resin printer on the horizon that can produce prints nearly instantaneously.

The method works similarly to existing resin printers by shining a specific light pattern on the resin in order to harden it. The main difference is that the resin is initially placed in a cylinder and spun at a high speed, and the light is shined on the resin at different angles with very precise intensities and timings in order to harden the resin in specific areas. This high-speed method allows the printer to produce prints in record-breaking time. The only current downside, besides the high price for the prototype printer, is that it’s currently limited to small prints.

With the ability to scale in the future and the trend of most new technologies to come down in price after they have been on the market for some amount of time, it would be groundbreaking to be able to produce prints with this type of speed if printers like these can be scalable. Especially if they end up matching the size and scale of homemade printers like this resin printer.

Thanks to [suicidal.banana] for the tip!

Portable MRI Machine Comes To The Patient

May 8, 2020 by 40 Comments

To say that the process of installing a magnetic resonance imager in a hospital is a complex task is a serious understatement. Once the approval of regulators is obtained, a process that could take years, architects and engineers have to figure out where the massive machine can be installed. An MRI suite requires a sizable electrical service to be installed, reinforced floors to handle the massive weight of the magnet, and special shielding in the walls and ceiling. And once the millions have been spent and the whole thing is up and running, there are ongoing safety concerns when working around a gigantic magnet that can suck ferromagnetic objects into it at any time.

MRI studies can reveal details of diseases and injuries that no other imaging modality can match, which justifies the massive capital investments hospitals make to obtain them. But what if MRI scanners could be miniaturized? Is there something inherent in the technology that makes them so massive and so expensive that many institutions are priced out of the market? Or has technology advanced far enough that a truly portable MRI?

It turns out that yes, an inexpensive MRI scanner is not only possible, but can be made portable enough to wheel into a patient care room. It’s not without compromise, but such a device could make a huge impact on diagnostic medicine and extend MRI technologies into places far beyond the traditional hospital setting.

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Building A Spinning Moiré Effect Lamp

December 28, 2019 by 7 Comments
A concise, comical explanation of Moiré patterns, via XKCD.

Moiré patterns are interference patterns created when grids of different size or alignment are placed over each other. You’ve probably seen these when photographing a TV screen or looking through a pair of windows screens at the same time. [ChrysN] put the effect to work with this spinning Moiré lamp build.

It’s a build that can be achieved with scrap-bin components. An LED-encrusted PC cooling fan is used as the base of the lamp, fitted with Sugru bumpers to hold a cheap glass vase. A line pattern is then printed on to paper, rolled into a cylinder, and slid on to the fan to spin with the blades, inside the vase. Another line pattern is then printed on to a transparency (a printable transparent sheet for those who don’t remember overhead projectors) and slid around the outside of the vase. When powered up, the LEDs glow, and the fan spins, creating a hypnotizing moving moiré pattern.

It’s a simple but visually captivating build, and one that should keep you up at night thanks to the blue LEDs. Moiré patterns can do so much more though – they’re even put to work guiding ships. Video after the break.

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Hackaday 10th Anniversary: Jon McPhalen And The Propeller

October 10, 2014 by 62 Comments

[Jon] came out to our 10th anniversary mini-con to talk about the Propeller, and judging from his short introduction, his hacker cred is through the roof. He has a page on IMDb, and his first computer was a COSMAC. Around 1993, he heard of a small company introducing the BASIC Stamp, and like us with most new technology was incredulous this device could perform as advertised. He tried it, though, and for a few years after that, he was programming the BASIC Stamp every single day.

Having a lot of blinky light project under his belt, [Jon] was always struggling with interrupts, figuring out a way to blink an LED exactly when he wanted it to blink. A lot has changed over at Parallax since 1993, and now they’re spending time with the Propeller, an 8-core microcontroller where interrupts are a thing of the past. He showed off a huge, 10-foot tall bear from League of Legends, all controlled with a single Propeller, using 1000 LEDs to look like fire and flames.

[Jon] shared the architecture of the Propeller, and the inside of this tiny plastic-encapsulated piece of silicon is wild; it’s eight 32-bit microcontrollers, all sharing some ROM and RAM, controlled by something called a Cog that gives each micro access to the address, data, and IO pins.

When the Propeller was first released, there were a few questions of how the chip would be programmed. C isn’t great for multicore work, so Parallax came up with a language called Spin. It’s written for multicore microcontrollers, and from [Jon]’s little session in demo hell, it’s not that much harder to pick up than Python. Remember that hour or two where you learned the syntax of Python? Yeah, learning Spin isn’t a huge time investment.

Even though you can program the Propeller in C and C++, there’s a reason for Spin being the official language of the Propeller. It isn’t even that hard, and if you want to dip your toes in multicore microcontroller programming, the Propeller is the way to do it. It’s an open source chip as well so you can give it a try with an FPGA board.

FPGA With Open Source Propeller 1 Running Spin

August 24, 2014 by 12 Comments

fpga-running-p8x32a-and-sidcog

Open Sourcing something doesn’t actually acquire meaning until someone actually uses what has been unleashed in the wild. We’re happy to see a working example of Propeller 1 on an FPGA dev board. That link takes you to a short description and some remapping of the pins to work with a BeMicro CV board. But you’ll want to watch the video below, or rather listen to it, for a bit more explanation of what [Sylwester] did to get this working.

You’ll remember that Parallax released the Propeller 1 as Verilog code a few weeks back. This project first loads the code onto the FPGA, then proves it works by running SIDcog, the Commodore 64 sound emulation program written in Spin for p8x32a processors.

We do find this to be an interesting first step. But we’re still waiting to see what type of hacks are made possible because of the newly available Verilog code. If you have a proof of concept working on other hardware, certainly tell us about it below. If you’ve been hacking on it and have something you want to show off, what are you waiting for?

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Internet Controlled Remote

September 10, 2010 by 41 Comments

How often does this happen to you? You’re leaving on a long trip, and half way there you remember the TV was left on. Never? Alright then, how about wanting to control an Xbox 360 from within the other room and you don’t have the remote. Still a rare occurrence?

Perhaps you have a better situation where an internet controlled IR remote, that can be programmed to work with any TV or IR accepting device, would be useful. [Nicholas McClanahan] starts off with USB Propeller from Parallax, adds an Ethernet module making a mini server, and ends with an IR LED and receiver. The code is nearly as simple being a combination of SPIN, Html, and JavaScript. All coming together under a nice website GUI that prompts for what IR signals to send. To make the project even more straightforward, [Nicholas] has included an Instructable as well. In the end though, while the hack is great, we’re still trying to find a decent enough use. Video after the rift.

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