MIDISWAY Promises To Step Up Your Live Show

October 8, 2017 by 13 Comments

If you like to read with gentle music playing, do yourself a favor and start the video while you’re reading about [Hugo Swift]’s MIDISWAY. The song is Promises, also by [SWIFT], which has piano phrases modulated during the actual playing, not in post-production.

The MIDISWAY is a stage-worthy looking box to sit atop your keys and pulse a happy little LED. The pulsing corresponds to the amount of pitch bending being sent to your instrument over a MIDI DIN connector. This modulation is generated by an Arduino and meant to recreate the effect of analog recording devices like an off-center vinyl or a tape that wasn’t tracking perfectly.

While recording fidelity keeps inching closer to perfect recreation, it takes an engineer like [Hugo Swift] to decide that a step backward is worth a few days of hacking. Now that you know what the MIDISWAY is supposed to do, listen closely at 2:24 in the video when the piano starts. The effect is subtle but hard to miss when you know what to listen for.

MIDI projects abound at Hackaday like this MIDI → USB converter for getting MIDI out of your keyboard once you’ve modulated it with a MIDISWAY. Maybe you are more interested in a MIDI fighter for controlling your DAW. MIDI is a robust and time-tested protocol which started in the early 1980s and will be around for many more years.

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Low-Tech Chair Enters The Matrix

October 8, 2017 by 37 Comments

This video demonstrates a really interesting experiment: sticking a Vive Tracker onto an ordinary chair in order to sync it up perfectly with its VR counterpart. The result? A chair that is visible in VR as a virtual object, but has a 1:1 physical world version occupying the same space. This means that unlike any other virtual object, this chair can be seen, touched, felt, moved, and actually sat in while the user is immersed in VR.

The purpose of this experiment seems to have been to virtually explore seating arrangements for real-world environments, and spawned a theatre planning tool by design studio [Agile Lens]. But we wonder if there’s unrealized potential in the idea of connecting physical objects that can be touched and held (or sat on) with their VR counterparts. Video demos of the chair test are embedded below.

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Hovering Questions About Magnetic Levitation

October 8, 2017 by 29 Comments

Who doesn’t love magnets? They’re functional, mysterious, and at the heart of nearly every electric motor. They can make objects appear to defy gravity or move on their own. If you’re like us, when you first started grappling with the refrigerator magnets, you tried to make one hover motionlessly over another. We tried to position one magnet over another by pitting their repellent forces against each other but [K&J Magnetics] explains why this will never work and how levitation can be done with electromagnets. (YouTube, embedded below.)

In the video, there is a quick demonstration of their levitation rig and a brief explanation with some handy oscilloscope readings to show what’s happening on the control side. The most valuable part, is the explanation in the article where it walks us through the process, starting with the reason permanent magnets can’t be used which leads into why electromagnets can be successful.

[K&J Magnetics]’s posts about magnets are informative and well-written. They have a rich mix of high-level subjects without diluting them by glossing over the important parts. Of course, as a retailer, they want to sell their magnets but the knowledge they share can be used anywhere, possibly even the magnets you have in your home.

Simpler levitators can be built with a single electromagnet to get you on the fast-track to building your own levitation rig. Remember in the first paragraph when we said ‘nearly’ every electric motor used magnets, piezoelectric motors spin without magnets.

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Your Hard Disk As An Accidental Microphone

October 8, 2017 by 30 Comments

We’re used to attaching peripherals to our computers, when we have a need for them to interact with the world around them. An Arduino Uno needs a shield to turn on the lights, for example. Just sometimes though there is the potential for unintended interaction between a computer and the real physical world which surrounds it, and it’s one of those moments that [Alfredo Ortega] has uncovered in his talk at the EKO Party conference in Buenos Aires. He demonstrates how a traditional spinning-rust computer hard disk interacts with vibration in its surroundings, and can either become a rudimentary microphone, or be compromised by sound at its resonant frequency (PDF).

It seems that you can measure the response time of the hard drive head during a read operation without requiring any privilege escalation. This timing varies with vibration, so can be used to reconstruct the sound that the drive is facing. Thus it becomes a microphone, albeit not a very good one with a profoundly bass-heavy response. He goes on to investigate the effect of sound on the drive, discovering that it has a resonant frequency at which the vibration causes it to be unreadable.

Sadly the talk itself appears not yet to be online, but given that previous years’ EKO talks are on YouTube it is likely that when the dust has settled you will be able to see it in full. Meanwhile he’s posted a video demonstration which we’ve posted below the break.

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Radio Tuning The Quicksilver Way

October 7, 2017 by 58 Comments

Modern radios are often digital affairs, in which the frequency is derived from a stable crystal oscillator and varied through a microprocessor controlled frequency synthesiser. It won’t drift, and it’s exactly on the frequency dialed in. Older radios though relied on a tuned circuit, a combination of capacitor and inductor, for their frequency selection. If you were curious enough to peer inside — and we know you were — you’d have seen the moving vanes of a variable capacitor controlled by the tuning knob.

Of course, there is another way to adjust a tuned circuit: by changing the value of the inductor. Older car radios for instance moved a ferrite slug inside a coil to tune from station to station. But that method is not good enough for [David Mills]. Being in possession of some finely graduated syringes he decided to try liquid tuning by increasing the volume within the coil.

Solutions of salts made little difference, so he reached for some mercury. The result is an RF inductor wound round a syringe body, with a body of mercury whose position can be adjusted by the plunger. He measures the Q factor of the coil with air core or mercury core, and as the inductance decreases with more mercury, so does the Q.

We see home-made parts from time to time, and there’s nothing too special about permeability tuning. However, this unusual take on the matter makes this one rather special. We doubt we’ll see its like very often in the future.

SpiderMAV drone perching from the ceiling

SpiderMAV Drone Shoots Webs To Perch And Stabilize

October 7, 2017 by 8 Comments

Introducing your friendly neighborhood SpiderMAV, a micro aerial vehicle that shoots webbing to enable it to hang from ceilings and stabilize itself horizontally using low power. It’s inspired by the Darwin’s bark spider that spins a circular web with anchor lines up to 25 meters (82 feet) long.

SpiderMAV perching and stabilizing modules

For the DJI Matrice 100 drone to hang from a ceiling, a compressed gas cylinder fires a magnet with a trailing polystyrene line up to a steel beam. The line can then be reeled in to the desired length. For horizontal stabilization, line-trailing magnets are fired horizontally instead and then reeled in to tension the lines.

To test the effectiveness of the system, a cross wind was produced using a fan. With the DJI’s attitude-hold mode, maximum X, Y and Z deviations were 136, 386 and 106 mm respectively. With the stabilization, however, the deviations were reduced to 47, 80 and 74 mm. The power requirements were also reduced to essentially nil. Watch it in action in the videos below.

SpiderMAV is the brainchild of Imperial College London’s Aerial Robotics Laboratory, led by [Mirko Kovac], and is still experimental. For example, a magnet release mechanism has yet to be built in. Perhaps a sharp tug by the reeling mechanism, or a sudden thrust by the drone would release the magnets. Or the permanent magnets could be replaced with electromagnets, provided the required current doesn’t offset the efficiency gains. What solutions can you come up with? Let us know in the comments.

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Dog-POV: Canine Speed Indicator

October 7, 2017 by 16 Comments

[Johan Beyers] built an elegantly simple Dog Speedometer project that uses a POV display to display a running dog’s speed without the benefit of an accelerometer. Using an Arduino (looks like it might be a D-love) and a line of 5 LEDs, [Johan] built a dirt-simple POV — 39 lines of code — that times out the flashes so that an immobile viewer sees the dog’s speed. How do you know your pup’s loping speed? That’s the beauty of this project.

Instead of putting all of the LEDs in a line, they are arranged in a V-shape. Because of this spatial offset, the patterns flashed out only “look right” at the right speed. Each number is flashed at a different speed, so you just look for the least distorted numeral.

[Johan]’s code does only what it needs to get the job done. The character data are stored in arrays that are played back directly to the pins of PORTD — avoiding most of the usual Arduino-style complexity with pin definitions and other foolery.

POV displays can be leveraged to add pizzazz to any project — this CD-ROM POV clock and this wind-powered POV weather station come to mind.