I consider myself a fairly sharp guy. I’ve made a living off of being a scientist for over 20 years now, and I have at least a passing knowledge of most scientific fields outside my area. But I feel like I should be able to do something other than babble incoherently when asked about magnets. They baffle me – there, I said it. So what do I do about it? Write a Hackaday post, naturally – chances are I’m not the only one with cryptomagnetonescience, even if I just made that term up. Maybe if we walk through the basics together, it’ll do us both some good understanding this fundamental and mysterious force of nature.
[anfractuosus] has been reading magnetic stripe card… optically!
While hackers routinely read and write stripe cards, this is the first time we’ve reported on optically imaging and decoding data from the magnetic stripe. [anfratuosus] used a magnetic developer which is designed to allow visual inspection of the magnetic stripe. The developer uses micron sized iron particles in a suspension which are dropped onto the stripe. To the particles, the magnetic stripe looks like a series of magnets lined up. Long magnets represent 0s and short magnets 1s. With each bit the orientation of the magnet changes, something like the diagram to the right. The magnetic field is strongest where the poles meet. So the iron particles are attracted to these flux reversal points on the stripe creating a visible pattern . There’s an awesome video of the process in action below.
While magnetic developer was designed for debugging faulty recording systems [anfratuosus] went a step further scanning the “developed” card, and writing a tool to decode the images and extract the card data. [anfratuosus] doesn’t mention any particular application, we love this circuitous hack anyway!
[Rulof Maker] has a penchant for making nifty projects out of old electronics. The one that has caught our eye is a microphone made from parts of an old hard drive. The drive’s arm and magnet were set aside while the aluminum base was diagonally cut into two pieces. One piece was later used to reassemble the hard drive’s magnet and arm onto a wooden platform.
The drive’s arm and voice coil actuator are the key parts of this project. It was modified with a metal extension so that a paper cone cut from an audio speaker could be attached, an idea used in microphone projects we’ve previously featured. Copper wire scavenged from the speaker was then soldered to voice coil on the arm as well as an audio jack. In the first version of the Hard Drive Microphone, the arm is held upright with a pair of springs and vibrates when the cone catches sound.
While the microphone worked, [Rulof] saw room for improvement. In the second version, he replaced the mechanical springs with magnets to keep the arm aloft. One pair was glued to the sides of the base, while another pair recovered from an old optical drive was affixed to the arm. He fabricated a larger paper cone and added a pop filter made out of pantyhose for good measure. The higher sound quality is definitely noticeable. If you are interested in more of [Rulof’s] projects, check out his YouTube channel.
The idea of using nanobots to treat diseases has been around for years, though it has yet to be realized in any significant manner. Inspired by Purcell’s Scallop theorem, scientists from the Max Planck Institute for Intelligent Systems have created their own version . They designed a “micro-scallop” that could propel itself through non-Newtonian fluids, which is what most biological fluids happen to be.
The scientists decided on constructing a relatively simple robot, one with two rigid “shells” and a flexible connecting hinge. They 3D-printed a negative mold of the structure and filled it with a polydimethylsiloxane (PDMS) solution mixed with fluorescent powder to enable detection. Once cured, the nanobot measured 800 microns wide by 300 microns thick. It’s worth noting that it did not have a motor. Once the mold was complete, two neodymium magnets were glued onto the outside of each shell. When a gradient-free external magnetic field was applied, the magnets make the nanobot’s shells open and close. These reciprocal movements resulted in its net propulsion through non-Newtonian media. The scientists also tested it in glycerol, an example of a Newtonian fluid. Confirming Purcell’s Scallop theorem, the nanobot did not move through the glycerol. They took videos of the nanobot in motion using a stereoscope, a digital camera with a colored-glass filter, and an ultraviolet LED to make the fluorescent nanobot detectable.
The scientists did not indicate any further studies regarding this design. Instead, they hope it will aid future researchers in designing nanobots that can swim through blood vessels and body fluids. We don’t know how many years it will be before this becomes mainstream medical science, but we know this much: we will never look at scallops the same way again!
Ahh, toddlers. They’re as ham-fisted as they are curious. It’s difficult to have to say no when they want to touch and engage with the things that we love and want them to play with. [Shawn] feels this way about his son’s interest in the family Sonos system and engineered an elegant solution he calls Song Blocks.
The Sonos sits on a dresser that hides a RasPi B+. Using bare walnut blocks numbered 1-12, his son can use the Sonos without actually touching it. Each block has a magnet and an NFC tag. When his son sticks a block on the face of the right drawer containing embedded magnets and an NFC controller board, the B+ reads the tag and plays the song. It also tweets the song selection and artist.
The blocks themselves are quite beautiful. [Shawn] numbered them with what look like Courier New stamps and then burned the numbers in with a soldering iron. His Python script is on the git, and he has links to the libraries used on his build page. The Song Blocks demo video is waiting for you after the jump.
Up on the second level of World Maker Faire’s main hall, one could hear Technotronic’s hit “Pump up the Jam” playing again and again. We were expecting breakdancing robots, but upon investigating, what we found was something even better. [David Durlach] was showing off his Choreographed Iron Dust, a 9 x 9 grid of magnets covered in iron filings. The filings swayed and danced to the beat of the music, at times appearing more like ferrofluid than a dry material. Two LED lights shined on the filings from an oblique angle. This added even more drama to the effect as the light played on the dancing spikes and ridges.
While chatting with [David] he told us that this wasn’t a new hack. Choreographed Iron Dust made its debut at the Boston Museum of Science back in 1989. Suddenly the 80’s music made more sense! The dust’s basic control system hasn’t changed very much since the 1980’s. The magnets are actually a stack of permanent and electromagnets. The permanent magnet provides enough force to hold the filings in place. The electromagnets are switched on to make the filings actually dance.
Since it was designed in 1989, there were no Arduinos available. This project is powered by the most hacker friendly interface of the era: the PC’s parallel port. As one might imagine, [David] has been having a hard time finding PC’s equipped with parallel ports these last few years.
[David] wasn’t just showing off iron dust. Having spent so much time painstakingly animating the iron filings for various customers, he knew there had to be a better way. He’s come up with ChoreoV, a system which can take recorded video, live performances, or even capture a section of a user’s screen. The captured data can then be translated directly into light or motion on an art piece.
Computer animation is a task both delicate and tedious, requiring the manipulation of a computer model into a series of poses over time saved as keyframes, further refined by adjusting how the computer interpolates between each frame. You need a rig (a kind of digital skeleton) to accurately control that model, and researcher [Alec Jacobson] and his team have developed a hands-on alternative to pushing pixels around.
The skeletal systems of computer animated characters consists of kinematic chains—joints that sprout from a root node out to the smallest extremity. Manipulating those joints usually requires the addition of easy-to-select control curves, which simplify the way joints rotate down the chain. Control curves do some behind-the-curtain math that allows the animator to move a character by grabbing a natural end-node, such as a hand or a foot. Lifting a character’s foot to place it on chair requires manipulating one control curve: grab foot control, move foot. Without these curves, an animator’s work is usually tripled: she has to first rotate the joint where the leg meets the hip, sticking the leg straight out, then rotate the knee back down, then rotate the ankle. A nightmare.
[Alec] and his team’s unique alternative is a system of interchangeable, 3D-printed mechanical pieces used to drive an on-screen character. The effect is that of digital puppetry, but with an eye toward precision. Their device consists of a central controller, joints, splitters, extensions, and endcaps. Joints connected to the controller appear in the 3D environment in real-time as they are assembled, and differences between the real-world rig and the model’s proportions can be adjusted in the software or through plastic extension pieces.
The plastic joints spin in all 3 directions (X,Y,Z), and record measurements via embedded Hall sensors and permanent magnets. Check out the accompanying article here (PDF) for specifics on the articulation device, then hang around after the break for a demonstration video.