Visual Magnetic Fields

If you need help visualizing magnetic fields, these slow-motion video captures should educate or captivate you. Flux lines are difficult to describe in words, because magnet shape and strength play a part. It might thus be difficult to visualize what is happening with a conical magnet, for a person used to a bar magnet. We should advise you before you watch the video below the break, if you are repelled by the sight of magnetite sand clogging a bare magnet then flying on the floor, this is your only warning.

The technique and equipment are simple and shown in the video. A layer of black sand is spread on a piece of tense plastic to make something like a dirty trampoline, and a neodymium magnet is dropped in the middle. The bouncing action launches the sand and magnet simultaneously so they are hanging in the air and the particles can move with little more than air resistance.

These videos were all taken with a single camera and a single magnet. Multiple cameras would yield 3D visuals, and the intertwining fields of multiple magnets can be beautiful. Perhaps a helix of spherical magnets? What do you have lying around the hosue? In a twist, we can use magnets to simulate gas atoms and trick them into performing unusual feats.

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The Very Slow Movie Player Does It With E-Ink

Most displays are looking to play things faster. We’ve got movies at 60 frames per second, and gaming displays that run at 144 fps. But what about moving in the other direction? [Bryan Boyer] wanted to try this out, so he built the VSMP, or Very Slow Movie Player. It’s a neat device that plays back a movie at about 24 fph (frames per hour) on an e-ink display to demonstrate something that [Bryan] calls Slow Seeing, which, he says “helps you see yourself against the smear of time.” A traditional epic-length movie is now going to run you greater than 8,000 hours of viewing.

Artistic considerations aside, it’s an interesting device from a technical point of view. [Bryan] built it from a 7.4-inch e-ink display from Pervasive Displays. The controller is connected to a Raspberry Pi Zero, which is running a Python script to convert a frame of the movie file into a dithered file, then send it to the display. Because the Pi Zero isn’t a very fast computer, this takes some time, and thus the slow speed of the VSMP. Originally, [Bryan] had set it up to run as fast as the system could manage, which was about 25 seconds per frame, or about 2 frames per minute. He decided to slow it down a bit further to the more attractive multiple of 24 frames per hour to contrast with the 24 frames per second of the original movie. He did this by using a CRON job that kicks of the conversion script once every 2.5 minutes and increments the frame counter. All of this is topped off with a nice 3D-printed case that has a lovely interference pattern to make a rather neat and intriguing project.

Perhaps the best part of this is see a time-lapse of the VSMP — life moves quickly around it while 2001: A Space Odyssey plays at normal speed.

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Nvidia Transforms Standard Video Into Slow Motion Using AI

Nvidia is back at it again with another awesome demo of applied machine learning: artificially transforming standard video into slow motion – they’re so good at showing off what AI can do that anyone would think they were trying to sell hardware for it.

Though most modern phones and cameras have an option to record in slow motion, it often comes at the expense of resolution, and always at the expense of storage space. For really high frame rates you’ll need a specialist camera, and you often don’t know that you should be filming in slow motion until after an event has occurred. Wouldn’t it be nice if we could just convert standard video to slow motion after it was recorded?

That’s just what Nvidia has done, all nicely documented in a paper. At its heart, the algorithm must take two frames, and artificially create one or more frames in between. This is not a manual algorithm that interpolates frames, this is a fully fledged deep-learning system. The Convolutional Neural Network (CNN) was trained on over a thousand videos – roughly 300k individual frames.

Since none of the parameters of the CNN are time-dependent, it’s possible to generate as many intermediate frames as required, something which sets this solution apart from previous approaches.  In some of the shots in their demo video, 30fps video is converted to 240fps; this requires the creation of 7 additional frames for every pair of consecutive frames.

The video after the break is seriously impressive, though if you look carefully you can see the odd imperfection, like the hockey player’s skate or dancer’s arm. Deep learning is as much an art as a science, and if you understood all of the research paper then you’re doing pretty darn well. For the rest of us, get up to speed by wrapping your head around neural networks, and trying out the simplest Tensorflow example.

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Slow Motion Frame Will Be The New Magic Mirror

[Paul] created a frame that uses an Arduino and LEDs to create a slow motion illusion of a delicate item (like a flower or a feather). The effect is striking as you can see in the video below.

[Paul] had seen similar projects (both one-offs and sold as a product), but wanted to do his own take on it. The principle is simple: The device vibrates the objects at one frequency and strobes LEDs at a slightly different frequency (80 and 79.5 Hz, in this case). The difference between the frequencies (the beat frequency) is what your eye perceives as a very slow (0.5 Hz, here) motion.

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Tennis Ball Cannon With Clear Combustion Chamber

[hw97karbine] has made a pretty cool tennis ball cannon. While making a cannon of this sort is nothing new to us, we were impressed by the effort taken to get a stoichiometrically ideal mixture of 3.2% butane and air in the combustion chamber.

[hw97karbine] filled a syringe with butane and then dosed exact amounts into the chamber using a hole in the back. To control the air mixture he marked lines on the outside of the cylinder with magic marker. Simple but effective.

More rewarding than the methods was the cool slow-mo videography of the explosions in the chamber. You really have to check it out. [hw97karbine] shows clearly the difference between a well-balanced fuel to air mixture and a poorly balanced one. It’s one thing to say that more fuel does not mean better combustion, as we all remember from our personal potato cannon experiences, but it’s another thing entirely to see it.

[Via Reddit]

Hackaday Links: November 29, 2015

The Raspberry Pi Zero was announced this week, so you know what that means: someone is going to destroy a Game Boy Micro. If you’re interested in putting the Zero in a tiny handheld of your own design, here are the dimensions, courtesy of [Bert].

[Ahmed] – the kid with the clock – and his family are suing his school district and city for $15 Million. The family is also seeking written apologies from the city’s mayor and police chief.

There are a lot — a lot — of ‘intro to FPGA’ boards out there, and the huge variety is an example of how the ‘educational FPGA’ is a hard nut to crack. Here’s the latest one from a Kickstarter. It uses an ICE40, so an open source toolchain is available, and at only $50, it’s cheap enough to start digging around with LUTs and gates.

Over on Hackaday.io, [Joseph] is building a YAG laser. This laser will require a parabolic mirror with the YAG rod at the focus. There’s an interesting way to make one of these: cut out some acrylic and beat a copper pipe against a form. A little polish and nickel plating and you have a custom mirror for a laser.

You know those machines with wooden gears, tracks, and dozens of ball bearings? Cool, huh? Tiny magnetic balls exist, and the obvious extension to this line of thought is amazing.

[David Windestål] is awesome. Completely and totally awesome. Usually, he’s behind the controls of an RC plane or tricopter, but this time he’s behind a slo-mo camera, an RC heli, and a watermelon. That’s a 550-sized heli with carbon fiber blades spinning at 2500 RPM, shot at 1000 FPS.

How do you label your cables? Apparently, you can use a label printer with heat shrink tubing. Nothing else, even: just put heat shrink through a label maker.

High Speed Laser Based Camera Flash Trigger For Only $2

[Matt Kane] works at a really cool company in the UK where he recently finished working on the Triggertrap Ada — the highest-performance, most feature packed camera trigger out there. So just for fun, he decided to challenge himself again — could he make a super basic, super fast, bare-bones camera trigger for $2 instead?

At the most basic level this is just a laser pointer and a light sensor. When the object your photographing breaks the light path, the flash triggers. Typically this is done with an IR laser, but since he’s going for a low-cost system, he’ll use a basic 1mw red laser pointer — the only downfall is you might see it in the picture.

Next up is the sensor. Ideally we’d use a photodiode which is very fast, but also expensive. A photoresistor is cheap, but not fast enough. A nice medium between the two is a phototransistor, which is relatively fast, and cheap. Finally, we need a minimum trigger period to offset the flash. [Matt] thought about using a 555 timer but instead decided to just generate a pulse with an Attiny45.  Continue reading “High Speed Laser Based Camera Flash Trigger For Only $2”