MIDI DAC for Vintage Synth Hacks

A lot of classic synthesizers rely on analog control voltages to vary parameters; this is a problem for the modern musician who may want to integrate such hardware with a MIDI setup. For just this problem, [little-scale] has built a MIDI-controllable DAC for generating control voltages.

It’s a simple enough build – a Teensy 2 is used to speak USB MIDI to a laptop. This allows the DAC to be used with just about any modern MIDI capable software. The Teensy then controls a Microchip MCP4922 over SPI to generate the requisite control voltages. [little-scale]’s video covers the basic assembly of the hardware on a breadboard, and goes on to demonstrate its use with a performance using the MIDI DAC to control a Moog Mother 32 synth. [little-scale] has also made the code available, making it easy to spin up your own.

We can see this project being indispensable to electronic musicians working with banks of modular synths, making it much easier to tie them in with automation in their DAW of choice. This isn’t the first MIDI interfacing hack we’ve seen either – check out this setup to interface an iPad to guitar pedals.

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Making VR Controllers From The Ground Up

VR is going to be the next big thing in five to seven years, and with that comes the problem of what the controllers will look like. The Vive and PS Move are probably close to what the first successful consumer VR setup will look like, but there’s plenty of room for experimentation. [ShinyQuagsire] decided to experiment with VR, IMUs, and computer vision and managed to make a VR controller from the ground up.

The design of [Quagsire]’s VR controller is very similar to the PS Move controller: there’s a glowy ball on top of a Wii-nunchuckish controller. There’s a good reason for this design: a sphere projected onto a 2D surface is always a circle. By illuminating a sphere with an IR LED, [Quagsire] can get an OpenCV script to hone in on the controller.

One thing that was particularly hard for [Quagsire] was building the 3D printed controllers. The first hardware revision wasn’t designed for manufacturing on a 3D printer — there were curves everywhere and very few flat areas for bed adhesion. The second hardware revision corrected these problems, but there’s a world of difference between designing a 3D printable part and being able to calibrate and tune a 3D printer. In the end, [Quagsire] sent the files off to 3DHubs to put that whole ordeal behind him.

With the case printed, [Quagsire] filled it with IMU breakouts, buttons, and a tiny joystick. The brains of the controller is a Teensy 3.2 that has plenty of examples of how to transmit gyro data and button presses over serial. With that done, the only thing left to do was to tie everything together.

The controller worked, and [Quagsire] learned a lot in the process. Making VR controllers is hard, even though a lot of the project isn’t the optimal way of doing things. For the next iteration of this project, [Quagsire] might look at wireless, but for now the entire project is up on Github for everyone to take a look at.

Barely-There GSM GPS Tracker

What’s the most un-intrusive GPS you’ve ever seen? How about for a bike? Redditor [Fyodel] has built a Teensy-based GPS/GSM tracker that slides into your bike’s handlebars and really is out of sight.

The tracker operates on T-Mobile’s 2G service band — which will enable the device to work until about 2020 — since AT/T is phasing out their service come January. Since each positioning message averages 60 bytes, an IoT data plan is sufficient for moderate usage, with plans to switch over to a narrow-band LTE service when it becomes more affordable. [Fyodel] admits that battery life isn’t ideal at the moment, but plans to make it more efficient by using a motion sensor to ensure it’s only on when it needs to be.

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Swear Bleep Detecting Eyebrows

Swear on broadcast television and they’re going to bleep out the audio to protect the sensibilities of the general public. Swear bleeps are fairly standardised at 1kHz, or so [mechatronicsguy] tells us. You learn something new every day.

OK, it’s not as though there’s an ISO document somewhere detailing the exact tone to use when someone says a naughty word on camera, it is far more likely that a 1kHz tone is the most likely frequency to be at hand in a studio. It’s so ubiquitous that even audio engineers with nowhere near perfect pitch can identify it, and one to which an acquaintance of ours swears years of exposure have given his ears a selective notch filter.

Armed with this information, [mechatronicsguy] created a fun project. As a fan of the [electroBOOM] Youtube channel he made a set of LED eyebrows for a picture of his bleep-prone hero, and using a Teensy with its audio and FFT libraries he made them light up whenever a 1kHz tone is detected. It’s not the most amazing of hacks, but if you find yourself in need of a smile on a chilly November morning then maybe it’ll have the same effect on you as it did with us. He’s posted a quick video of the ‘brows in action which we’ve embedded below the break.

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Stormtrooper Voice Changer Helmet uses Teensy to Mangle Audio

Halloween has come and gone, but this DIY voice changing Star Wars Stormtrooper helmet tutorial by [Shawn Hymel] is worth a look for a number of reasons. Not only is the whole thing completely self-contained, but the voice changing is done in software thanks to the Teensy’s powerful audio filtering abilities. In addition, the Teensy also takes care of adding the iconic Stormtrooper clicks, pops, and static bursts around the voice-altered speech. Check out the video below to hear it in action.

Besides a microphone and speakers, there’s a Teensy 3.2, a low-cost add-on board for the Teensy that includes a small audio amp, a power supply… and that’s about it. There isn’t a separate WAV board or hacked MP3 player in sight.

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When a CRT Isn’t Retro Enough: LEDs

When we think of an old-style computer terminal, it has a CRT screen: either one of the big 1970s VDUs with integrated keyboard, or maybe one from a later decade with more svelte styling. You would have found other displays in use in previous decades though, and one of them came our way that we think it worthy of sharing.

16 segments in action. (PD) Wikimedia Commons.

[Dan Julio] was given several tubes of Siemens DL1416B 4-digit 17-segment LED displays by a friend, and decided to use them as an unusual retro display for his terminal project. These devices are an alphanumeric display with a parallel interface that can show a subset of the ASCII character set as well as a cursor. He had 213 of them, so made plans for a 64 character by 16 line display, however on discovering a quantity of the parts were non-functional he had to scale back to 12 lines of 48 characters.

The terminal in action.
The terminal in action.

The displays are mounted on PCBs in groups of four, controlled by a PIC16F1459 and some shift registers. These boards are then daisy-chained via a TTL serial line. The whole display shares one of the three serial ports on a Teensy 3.1 with his retro keyboard that has its own PIC controller, the others serving a serial printer port and the terminal serial port. The Teensy software has two modes: serial terminal or a Tiny Basic interpreter, and the relevant repositories are linked from the project page.

Since each set of DL1416Bs takes 250 mA, the whole display consumes about 9 A at 5 volts. On top of that the keyboard uses another 500 mA, so a sufficiently powerful supply had to be incorporated. This is mounted along with the Teensy in a very well-made enclosure, and the whole is mounted on what looks like a surplus monitor stand for a very professional finish.

To take us through the terminal’s features he’s posted a YouTube video that we’ve placed below the break. It comes across as a surprisingly usable machine, as he logs into a Raspberry Pi and edits a file, and takes us through some features of the BASIC interpreter.

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Hacklet 126 – Teensy Projects

The Arduino has proved to be a great platform for electronics projects. The same goes for the Raspberry Pi. However, there are some projects that fall in the gap between these two options. Projects that need more memory or processing power than the ATmega microcontrollers have to offer, but not so much as to require a full Linux/ARM powerhouse. For those projects, there is the Teensy series. [Paul Stoffregen] created these lilliputian boards, and he’s been adding features ever since. The thousands of Teensy projects out there stand as proof that these little boards have been well received by the hacker community. This week’s Hacklet is about some of the best Teensy projects on Hackaday.io!

beatsWe start with [Jonathan Payne] and Beats by Teensy. Beats is an all in one music machine. A sampler, sequencer, and MIDI control surface; all powered by the Teensy 3.1 and the Teensy Audio Board. The audio board gives Beats the ability to record and playback 16 bit audio at a sampling rate of  up to 44.1 kHz. [Jonathan’s] inspiration came from devices such as the Akai MPC, and the MIDI Fighter. He utilized the incredible Teensy audio library on the software side. A project like this needs a serious case. [Jonathan] designed and built the perfect panel and case utilizing arcade buttons and a 128×64 LCD from Adafruit.

sabNext we have [RF William Hollender] and Teensy Super Audio Board. Not satisfied with CD quality 44.1 kHz audio, [William] decided to add a high quality audio codec to Teensy’s bag of tricks. He picked the CS4272 codec from Cirrus Logic. Capable of sampling rates up to 192 kHz, with a THD+N of -100 db, this codec should please all but the most discerning audiophiles. The high noise immune design doesn’t stop there though. [William’s] design isolated the Teensy and the rest of the interfaces from the codec to prevent ground loops. Connectivity is via standard I2S for the audio stream and I2C for control. This means the super audio board can be used with Raspberry Pi’s and the like.

spinoNext up is [Spino] with Spino. Teensy boards can do a lot more than just audio. Spino is a POV display with 32 spinning RGB LEDs. Spino can do more than just show pretty pictures though. With a Teensy 3.2 and bluetooth radio on board, the spino team is able to play games on their display. LEDs don’t work exactly like CRTs and LCDs though, so some color changes were necessary. The team utilized cell shading with a sobel filter to make Doom look even better than ever. The Teensy is even powerful enough to handle live webcam video sent over USB. The video is rendered and displayed on the spinning LEDs.

megsyFinally we have [Tim Trzepacz] with Megsy? A homebrew Teensy 3++. [Tim] is working on Megsy as part of his  residency at the Supplyframe Design Lab. Teensy’s have lots of edge mounted IO pins. There isn’t enough real estate for all the pins though, so some are routed to pads on the bottom. Megsy is a Teensy carrier board that breaks these pads out to pins. The idea is to solder the Teensy directly do the Megsy. As [Tim] calls it, “a poor man’s BGA”. The problem is getting the solder hot enough to melt while sandwiched between two insulating PCBs. [Tim’s] first attempt netted him a rather scorched Megsy board. Blacked as it may have been, the board did work!

If you want to see more Teensy projects, check out our new Teensy projects list. Notice a project I might have missed? Don’t be shy, just drop me a message on Hackaday.io. That’s it for this week’s Hacklet, As always, see you next week. Same hack time, same hack channel, bringing you the best of Hackaday.io!