Black MIDI: There Is No Denser Music

November 12, 2015 by Elliot Williams 73 Comments

Imagine if you played all the keys on a piano at once. What would it sound like? Now imagine that you’d like to transcribe that music. What would it look like? So many notes that you could hardly see the paper underneath.

Which is why the people making such “impossible music” are calling themselves the Black MIDI Crew: if you wrote the music down, it’d look like a big black blob. Or at least, that’s the joke. Amazingly, though, it doesn’t sound like a big mess. Check out “Pi, The Song With 3.1415 Million Notes” below the break to see what we mean.

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Adding Range (and Bling) To An Electric Skateboard

November 10, 2015 by Elliot Williams 5 Comments

Long-time Hackaday reader [Andrew Rossignol] bought a Boosted-brand electric skateboard while he was living in NYC. While the batteries more than sufficed for his commute in the Big Apple, he ran out of juice when he moved to the Left Coast, leaving him three miles short of a ten mile trip.

Faced with the unthinkable fate of pushing his skateboard like a Neanderthal, [Andrew] added more batteries. There’s great detail about how he chose the battery chemistry and the particulars of charging and something about load balancing, so it’s definitely worth a read if you’re building an electric vehicle.

But once [Andrew] had some surplus battery capacity on board (tee hee!) he thought of ways to waste it. The natural solution: tons of RGB LED underlighting.

Still not content with an off-the-shelf solution (which wouldn’t let him recharge the batteries without unplugging the lights), he ended up rolling his own with an Arduino and some WS2812s. The nicest touch? Keeping it all out of the elements in a sweet aluminum box, hiding the cable salad within.

There’s a lot to be said for the good industrial design of something like the Boosted skateboard, but if you’d rather DIY, we’ve been covering electric skateboard for a while now. It’s nice to see how battery and motor technology have changed since then, too. Compare and contrast this recent build with that old-school version and with [Andrew’s] build that was covered in this post. We live in good times.

Your Unhashable Fingerprints Secure Nothing

November 10, 2015 by Elliot Williams 95 Comments

Passwords are crap. Nobody picks good ones, when they do they re-use them across sites, and if you use even a trustworthy password manager, they’ll get hacked too. But you know what’s worse than a password? A fingerprint. Fingerprints have enough problems with them that they should never be used anywhere a password would be.

Passwords are supposed to be secret, like the name of your childhood pet. In contrast, you carry your fingers around with you out in the open nearly everywhere you go. Passwords also need to be revocable. In the case that your password does get revealed, it’s great to be able to simply pick another one. You don’t want to have to revoke your fingers. Finally, and this is the kicker, you want your password to be hashable, in order to protect the password database itself from theft.

In the rest of the article, I’ll make each of these three cases, and hopefully convince you that using fingerprints in place of a password is even more broken than using a password in the first place. (You listening Apple and Google? No, I didn’t think you were.)

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Two Turntables And No Microphone

November 9, 2015 by Elliot Williams 23 Comments

It used to be that you had to spend real money to get an alternative controller for your electronic musical arsenal. These days, with cheap microcontrollers and easily-accessible free software libraries, you can do something awesome for pocket change. But that doesn’t mean that you can’t make a sexy, functional piece of art along the way! [Jan Godde] did just that with his cleverly named Wooden Sensor Box With Two Rotary Disks. (If you’ve got a better name for this thing, toss it in the comments.)

From what we can see, the box has two potentiometer sliders, two touch-sensitive potentiometers, two force sensitive resistors, a slew of knobs, and a whole bunch of (capacitive?) touch points. In short, a ton of continuous controllers of all sizes and shapes in an aesthetic case. But stealing the show, and giving the device its name, are two platters from old hard drives that serve as jog wheels.

As shown in the video below the break, the two jog wheels are covered with alternating stripes on the underside. Each platter has a dedicated pair of IR LEDs and photodetectors underneath serving as a quadrature encoder that allows [Jan] to tell which direction the platters are rotating, and how far.

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Synth Secrets Exposed!

November 8, 2015 by Elliot Williams 2 Comments

If you’re at all interested in synthesizers, but haven’t gotten as deep into programming them as you’d like, you absolutely need to check out the old “Synth Secrets” column from Sound on Sound magazine. Across 63(!) articles, the author [Gordon Reid] takes a practical approach to learning synthesizers: trying to copy the sound of one real instrument at a time, with concrete examples built up on one particular synthesizer.

[Gordon]’s approach to synthesis is straightforward, but that’s exactly what makes it useful. After the first couple articles, which introduce you to the common functions of many synthesizers, most articles follow a simple pattern: listen to the instrument’s characteristic sounds, look to the physics behind how it produces them, and then figure out how to replicate as much of the sound as is necessary (or possible) to capture the essence of the instrument. Sometimes when the instrument’s sounds are particularly complex, as in this series of articles on the violin, he’ll break this simple formula up across multiple articles.

Now you might complain that you don’t have a Korg MS-20 or an ARP Odyssey or whatever particular old synth is being used in any particular article. But the “Secrets” are actually so fundamental, and by-and-large worked out on such simple analog synths, that even if you can’t make exactly the same sounds as [Gordon] does, you’ll understand how he got where he got, you’ll probably get pretty close, and you’ll have tuned up your ears along the way.

Plus, you’ll learn a tremendous amount about the character and capabilities of your synthesizer by trying. Working through the “Synth Secrets” examples would be a great way to get to know a new synth in your rack, even if you’re only into space noise and not interested in reproducing real instruments.

But if you are into space noise, also check out our own Logic Noise series. You won’t learn anything about real instruments, but you’ll learn a heck of a lot about the 4000-series logic chips and the abuse thereof.

Thanks [Greg Kennedy] for reminding us of this gem, and for re-installing the “Synth Secrets” bee in our bonnet!

Compressorhead: Best Robot Band Ever?

November 7, 2015 by Elliot Williams 12 Comments

We’ve written about Compressorhead before but we’re writing about them again. Why? Because Compressorhead is the most amazing robot band you’ve ever seen, and because they’ve just opened up a Kickstarter to fund building a lead singer robot and recording an album.

And because they’ve released a bunch of new videos, one of which you’ll find below the break.

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Low Power And Pin-Constrained

November 7, 2015 by Elliot Williams 30 Comments

We’ve all been there. You’re building up a microcontroller project and you wish that you could just add “one more feature” but you’re limited by the hardware. Time to start thinking. (Or, arguably, buy the next model up.)

[Sam Feller] found himself in this position, adding a knob to set the time and a button to arm the alarm for his Analog Voltmeter Clock, and he came up with a way to implement an on-off switch, and poll a button and a potentiometer with only two pins of a microcontroller.

The problem with potentiometers in low-power designs is that they’re always leaking power. That is, unless you switch them off when you’re not using them. So the ideal solution is to power the potentiometer from one GPIO pin on the microcontroller, and read its value with another. That’s two GPIO pins just for the potentiometer. But [Sam] needed to read input from a button too, and he was out of pins.

Not pressed: pot sees VCC and VCC/2

Pressed: pot sees VCC/2 and GND

His clever solution is to switch two resistors in or out of the circuit depending on the status of the pushbutton, so that the voltage range at the potentiometer is between either VCC and VCC/2 when the switch is pressed, or between VCC/2 and GND when the switch is not pressed.

If the ADC reads something higher than VCC/2, the microcontroller knows that the button is pressed, and vice-versa. The potentiometer’s setting determines exactly where the voltage lies within either range.

Done and done. If you find yourself in the similar situation of needing to read in values from a whole bunch of buttons instead of a potentiometer, then you can try using an R-2R DAC wired up to the pushbuttons and reading the (analog) value to figure out which buttons are pressed. (If you squint your eyes just right, this solution is the same as the R-2R DAC one with the potentiometer replacing all but the most-significant bit of the R-2R DAC.)

Another tool for the toolbox. Thanks [Sam].