Acoustic Levitation with a Twist

Don’t blame us for the click-baity titles in the source articles about this handheld “acoustic tractor beam”. You can see why the popular press tarted this one up a bit, even at the risk of drawing the ire of Star Trek fans everywhere. Even the journal article describing this build slipped the “tractor beam” moniker into their title. No space vessel in distress will be towed by [Asier Marzo]’s tractor beam, unless the aliens are fruit flies piloting nearly weightless expanded polystyrene beads around the galaxy.

That doesn’t detract from the coolness of the build, revealed in the video below. There’s no tutorial per se, but an Instructables post is promised. Still, a reasonably skilled hacker will be able to replicate the results with ease straight from the video. Using mostly off the shelf hardware, [Marzo] creates a bowl-shaped phased array of ultrasonic transducers driven by an Arduino through a DC-DC converter and dual H-bridge driver board to boost the 40 kHz square waves from 5 Vpp to 70 Vpp. By controlling the phasing of the signals, the tractor beam can not only levitate small targets but also move them axially. It looks like a lot of fun.

Acoustic levitation is nothing new here – we’ve covered 3D acoustic airbending, as well as an acoustic flip-dot display. Being able to control the power of sound waves in a handheld unit is a step beyond, though.

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JOLED – a 3D Flip Dot Display

Flip-Dot displays are so awesome that they’re making a comeback. But awesome is nothing when you can have an insane flip-dot display that is three-dimensional with the dots floating in mid-air. Researchers at the Universities of Sussex and Bristol have built what they call JOLED, an array of floating pixels that can be controlled via a combination of ultrasonic standing waves and an electrostatic field. These “voxels” can be individually moved in space via ultrasonics, and can also be individually flipped or rotated through any angle, via the electrostatic field.

The key to the whole thing is something they call Janus Objects – hence JOLED. Janus particles have different features or chemistry on two opposite sides. A portion of each voxel is speckled with a small amount of titanium dioxide nano powder. This gives it a bipolar charge that makes it respond to the variable electrostatic field and hence capable of axial rotation. Half of each white voxel can then be covered with a contrasting color – red, blue, black – to achieve the flip dot effect. Each voxel appears to be a couple of millimeters in diameter. The ultrasonic actuators appear to be regular piezo transmitters found in every hacker’s parts bin. Transparent glass plates on opposite sides apply the variable electrostatic field.

While this is still experimental and confined to the research lab, future applications would be interesting. It would be like breaking e-ink displays out of their flat glass confines and giving them a third dimension. The short, two-minute video after the break does a good job of explaining what’s going on, so check it out. Now, who want’s to be the first to build a JOLED clock?

Thanks to [Garrow] for tipping us off about this.

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A Developer’s Kit for Medical Ultrasound

From watching a heart valve in operation to meeting your baby before she’s born, ultrasound is one of the most valuable and least invasive imaging tools of modern medicine. You pay for the value, of course, with ultrasound machines that cost upwards of $100k, and this can put them out of reach in many developing countries. Sounds like a problem for hackers to solve, and to help that happen, this 2016 Hackaday prize entry aims to create a development kit to enable low-cost medical ultrasounds.

PhysicalSpaceDeveloped as an off-shoot from the open-source echOpen project, [kelu124]’s Murgen project aims to enable hackers to create an ultrasound stethoscope in the $500 price range. A look at the test bench reveals that not much specialized equipment is needed. Other than the Murgen development board itself, everything on the test bench is standard issue stuff. Even the test target, an ultrasound image of which leads off this article, is pretty common stuff – a condom filled with tapioca and agar. The Murgen board itself is a cape for a BeagleBone Black, and full schematics and code are available.

We’ll be paying close attention to what comes out of the ultrasound dev kit. Perhaps something as cool as this augmented reality ultrasound scope?

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Augmented Reality Ultrasound

Think of Virtual Reality and it’s mostly fun and games that come to mind. But there’s a lot of useful, real world applications that will soon open up exciting possibilities in areas such as medicine, for example. [Victor] from the Shackspace hacker space in Stuttgart built an Augmented Reality Ultrasound scanning application to demonstrate such possibilities.

But first off, we cannot get over how it’s possible to go dumpster diving and return with a functional ultrasound machine! That’s what member [Alf] turned up with one day. After some initial excitement at its novelty, it was relegated to a corner gathering dust. When [Victor] spotted it, he asked to borrow it for a project. Shackspace were happy to donate it to him and free up some space. Some time later, [Victor] showed off what he did with the ultrasound machine.

As soon as the ultrasound scanner registers with the VR app, possibly using the image taped to the scan sensor, the scanner data is projected virtually under the echo sensor. There isn’t much detail of how he did it, but it was done using Vuforia SDK which helps build applications for mobile devices and digital eye wear in conjunction with the Unity 5 cross-platform game engine. Check out the video to see it in action.

Thanks to [hadez] for sending in this link.

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Find and Repair a 230kV 800Amp Oil-Filled Power Cable Feels Like Mission Impossible

How do you fix a shorted cable ? Not just any cable. An underground, 3-phase, 230kV, 800 amp per phase, 10 mile long one, carrying power from a power station to a distribution centre. It costs $13,000 per hour in downtime, counting 1989 money, and takes 8 months to fix. That’s almost $75 million. The Los Angeles Department of Water and Power did this fix about 26 years ago on the cable going from the Scattergood Steam Plant in El Segundo to a distribution center near Bundy and S.M. Blvd. [Jamie Zawinski] posted details on his blog in 2002. [Jamie] a.k.a [jwz] may be familiar to many as one of the founders of Netscape and Mozilla.

To begin with, you need Liquid Nitrogen. Lots of it. As in truckloads. The cable is 16 inch diameter co-axial, filled with 100,000 gallons of oil dielectric pressurised to 200 psi. You can’t drain out all the oil for lots of very good reasons – time and cost being on top of the list. That’s where the LN2 comes in. They dig holes on both sides (20-30 feet each way) of the fault, wrap the pipe with giant blankets filled with all kind of tubes and wires, feed LN2 through the tubes, and *freeze* the oil. With the frozen oil acting as a plug, the faulty section is cut open, drained, the bad stuff removed, replaced, welded back together, topped off, and the plugs are thawed. To make sure the frozen plugs don’t blow out, the oil pressure is reduced to 80 psi during the repair process. They can’t lower it any further, again due to several compelling reasons. The cable was laid in 1972 and was designed to have a MTBF of 60 years.

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Blackboard digitization for under $40

Digital White/Black Boards or “Smart Boards” are very useful in modern classrooms, but their high cost often makes it difficult to convince administrators from loosening their purse strings. Cooper Union’s 2nd annual HackCooper event in New York wanted students to design and build hardware and software projects that both solve real problems and spark the imagination. At the 24 hour hackathon, the team of [harrison], [david] and [caleb] decided to put together a low-cost and simple solution to digitizing classroom black board content.

A chalk-holder is attached to two strings, each connected over a pulley to a weight. The weights slide inside PVC pipes at the two sides of the black board. Ultrasonic sensors at the bottom of each tube measure the distance to the weights. The weights sit in static equilibrium, so they serve the purpose of keeping the string taut without negatively interfering with the writer.

With a couple of calibration points to measure the extent of displacement of each weight, board width can be determined, making it easy to adapt to different sizes of boards. Once calibrated, the system can determine position of the chalk over the board based on some trigonometrical calculations. Since they had just 24 hours to hack the system together, they had to use a hand operated radio with a couple of buttons to provide user control. Pressing the “Write” button starts transmitting chalk movements to the digital screen. A second button on the radio remote serves to “Erase” the digital screen. After receiving the chalk position data, they had to do a fair amount of processing to eliminate noise and smooth out the writing on the digital screen.

A server allows the whole class to receive the chalk board data in real time. After each “Erase” command, the chalk board state is saved and logged on the server, thus allowing previous content to be viewed or downloaded. If only text is written, optical character recognition can be used to further digitize the content.

What makes the project really useful is the low cost. The sensors cost a dollar. The other parts – PVC pipe, weights/pulleys, Arduino and the Radio key fob – were all bought for under 40 dollars. For some additional cost (and maybe more time in their case) they could have automated the detection of when the chalk was actually doing the writing. The team have made their code available on Github. For a Chalk board at the other end of the cost spectrum, check this one out. Video below.

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Know Your Speed on Rollerblades

[Anurag] is a computer engineering student with a knack for rollerblading. Rollerblades are not a transportation device that are often fitted with speedometers, so [Anurag] took that more as a challenge and designed this Arduino-powered computer to give him more information on his rollerblade rides.

The device uses an Arduino as the brain, and counts wheel revolutions (along with doing a little bit of math) in order to calculate the speed of the rider. The only problem with using this method is that the wheels aren’t on the ground at all times, and slow down slightly when the rider’s foot is off the ground. To make sure he gets accurate data, the Arduino uses an ultrasonic rangefinder to determine the distance to the ground and deduce when it should be taking speed measurements.

In addition to speed, the device can also calculate humidity and temperature, and could be configured to measure any number of things. It outputs its results to a small screen, but it could easily be upgraded with Bluetooth for easy data logging. If speed is truly your goal, you might want to have a look at these motorized rollerblades too.