MIDI to CV The DIY Way

MIDI has been a remarkably popular interface since its inception way back in 1983. Based on existing serial interfaces, and with a broad enough set of features, it remains the defacto standard for communication between musical gear. However, older gear and many modular synths simply don’t grok digital data, instead using analog control voltages to get the job done. Never fear, though – you can convert from one to the other with the goMIDI2CV.

It’s a simple device, hewn from an ATTINY microcontroller. MIDI signals are received at TTL voltage levels, and converted to output voltages by the ATTINY via use of the PWM hardware. A lowpass filter is added to remove the high-frequency content from the output signal.  A 6N138 optocoupler completes the project, to comply with the MIDI standard and ensure the device is not subject to any dangerous voltages from the hardware plugged in.

It’s a simple way to control older non-MIDI compliant hardware, and might make an old modular rig just that much more useful in the studio of today. We’ve seen similar builds before, like this combined CV and Gate converter. 

Alexa, Attack Intruders

If our doom at the hands of our robot overlords is coming, I for one welcome the chance to get a preview of how they might go about it. That’s the idea behind Project Icarus, an Alexa-enabled face-tracking Nerf turret. Designed by [Nick Engmann],  this impressive (or terrifying) project is built around a Nerf Vulcan, a foam dart firing machine gun mounted on a panning turret that is hidden behind a drop-down cabinet door. This is connected to a Pi Zero equipped with a Pi camera. The Zero is running OpenCV and Google Firebase, which connects it with Amazon’s Alexa service.

It works like this: you say “Alexa, open Project Icarus”. Through the Alexa skill that [Nick] created, this connects to the Pi and starts the system. If you then say “Alexa, activate alpha”, it triggers a relay to open the cabinet and the Nerf gun starts panning around, while the camera mounted on the top of it searches for faces. The command “Alexa, activate beta” triggers the Nerf to open fire.

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Mechanisms: Couplings

I was splitting wood one day a few years back, getting next winter’s firewood ready on my hydraulic splitter. It normally handled my ash and oak with ease, but I had a particularly gnarly piece of birch queued up, and the splitter was struggling. The 20-ton cylinder slowed as the wedge jammed in the twisted grain, the engine started to bog down, then BANG! I jumped back as something gave way and the engine revved out of control; I figured a hydraulic hose gave out. Whatever it was, I was done for the day.

I later discovered that a coupler between the engine shaft and the hydraulic pump failed dramatically. It was an easy fix once I ordered the right part, and I’ve since learned to keep extras in stock. Couplings are useful things, and they’re the next up in our series on mechanisms.

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Pop Goes the Haunted Jack-in-the-Box

Is Halloween sneaking up on you, too?  It’s less than two weeks away, but there is still plenty of time to build something that will scare the pants off trick-or-treaters and party guests alike. This year, Hackaday regular [Sean Hodgins] hacked his favorite holiday by taking something that ships with a base level of scariness and making it autonomous. What could be more frightening than a haunted toy?

The (decades-old) jack-in-the-box mechanism is simple. Turning the crank operates a mechanical music box that plays the traditional “Pop Goes the Weasel”. When the music box hits the high note, a jutting piece of plastic on the barrel of music box disturbs the other end of the latch, which frees the scary clown inside. [Sean] used a 100:1 DC motor to turn the crank from the inside, and a Pi camera to detect victims in the vicinity. Once the camera locks on to a face, the box cranks itself and eventually ejects the jester. Since most of the space inside is already taken up by the spring, [Sean] housed the electronics in a custom 3D-printed base with a hole cut out for the camera’s eye.

Many modifications are possible with a project like this. [Sean] is now in complete control of the latch operation, so he could make the clown pop appear instantly, or randomly, or sometimes not at all. Check out [Sean]’s entertaining build video after the break.

Want to make your own fright machine from scratch? We’ve got all the inspiration you need, from tabletop to trash can-sized monsters. Continue reading “Pop Goes the Haunted Jack-in-the-Box”

MIDI to CV/Gate The Easy Way

Let’s say you’ve got a modular synthesizer. You’re probably a pretty cool person. But all your cool laptop DJ friends keep showing off their MIDI-controlled hardware, and you’re getting jealous. Well, [little-scale] has the build for you.

The Teensy 3.6 is the current top-of-the-line Teensy from PJRC, and it’s [little-scale]’s weapon of choice here. With USB-MIDI and two 12-bit DACs on board, it’s made creating an interface between the worlds of analog and digital music into a remarkably simple job. Control voltages for pitch and velocity are pushed out over the analog pins, while pin 29 is used for gate signals.

It’s a testament to the amount of development that has gone into the Teensy platform that such projects can be built with virtually no off-board components. The build is a further step forward in simplicity from [little-scale]’s previous work, using a Teensy 2 with an offboard DAC to generate the output voltages.

Here at Hackaday, we’ve always been big fans of adding computer control to analog hardware. This CNC mod to a guitar pickup winding machine is a great example.

Hackaday Links: September 17, 2017

BREAKING NEWS: APPLE HAS RELEASED A NEW RECTANGLE. IT IS BETTER THAN THE PREVIOUS RECTANGLE, WHICH WAS A LESSER RECTANGLE. SOME PEOPLE ARE UNHAPPY WITH THE NEW RECTANGLE BECAUSE OF [[CHANGES]]. THE NEW RECTANGLE HAS ANIMATED POO.

Mergers and acquisitions? Not this time. Lattice Semiconductor would have been bought by Canyon Bridge — a private equity firm backed by the Chinese government — for $1.3B. This deal was shut down by the US government because of national security concerns.

[Jan] is the Internet’s expert in doing synths on single chips, and now he has something pretty cool. It’s a breadboard synth with MIDI and CV input. Basically, what we’re looking at is [Jan]’s CVS-01 chip for a DCO, DCF, and DCA), a KL5 chip for an LFO, and an envelope chip. Tie everything together with a two-octave captouch keyboard, and you have a complete synthesizer on a breadboard.

As an aside relating to the above, does anyone know what the cool kids are using for a CV/Gate keyboard controller these days? Modular synths are making a comeback, but it looks like everyone is running a MIDI keyboard into a MIDI-CV converter. It seems like there should be a –simple, cheap– controller with quarter-inch jacks labeled CV and Gate. Any suggestions?

World leaders are tweeting. The Canadian PM is awesome and likes Dark Castle.

Way back in July, Square, the ‘POS terminal on an iPad’ company posted some data on Twitter. Apparently, fidget spinner sales peaked during the last week of May, and were declining through the first few weeks of summer. Is this proof the fidget spinner fad was dead by August? I have an alternate hypothesis: fidget spinner sales are tied to middle schoolers, and sales started dropping at the beginning of summer vacation. We need more data, so if some of you could retweet this, that would be awesome.

Remember [Peter Sripol], the guy building an ultralight in his basement? This is going to be a five- or six-part video build log, and part three came out this week. This video features the installation of the control surfaces, the application of turnbuckles, and hardware that is far too expensive for what it actually is.

Augmented Reality Pinball

Pinball machines are fascinating pieces of mechanical and electrical engineering, and now [Yair Moshe] and his students at the Israel Institute of Technology has taken the classic game one step further.  Using computer vision and a projector, this group of engineers has created an augmented reality pinball game that takes pinball to a whole new level.

Once the laptop, webcam, and projector are set up, a course is drawn on a whiteboard which the computer “sees” to determine the rules of the game. Any course you can imagine can be drawn on the whiteboard too, with an interesting set of rules that no regular pinball game could take advantage of. Most notably, the ball can change size when it hits certain types of objects, which makes for a very interesting and unconventional style of play.

The player uses their hands to control the flippers as well, but not with buttons. The computer watches the position of the player’s hands and flips the flippers when it sees a hand in the right position. [Yair] and his students recently showed this project off at DLD Tel Aviv and even got [Shimon Perez], former President of Israel, to play some pinball at the conference!