Enginursday: The Macchiato Synth and MIDI Tools

via SparkFun Electronics Blog Posts

I’ve got a new synthesizer to show today, fresh from Zeppelin Design Labs. This video continues on the synth theme and shows off what this spry little kit, called the Macchiato Mini Synth, can do. Then I connect it up with some MIDI tools I built from SparkFun products to show how you really can get exactly what you want when you build with open source.

Have a look, and then read a bit about the parts and components used in the video.

The Macchiato Mini Synth

This came to me as a prototype kit, which assembled easily and was fun to build. Check out the product page, or the end of the assembly manual, for a schematic. This runs an ATMega644pa processor at 16MHz to get extra IO and twice the memory of a 328p. It can be reprogrammed with our Pocket AVR Programmer.

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Key features of the synthesizer:

  • Two-voice polyphony
  • Capacitive touch keyboard
  • Wave shape select
  • Amplitude envelope
  • LFO modulation to filter
  • 1-inch onboard speaker
  • Audio Out — accepts 3.5mm (1/8") TRS or TRRS male jack
  • ISP header for PC connection (to upload software updates/mods)

Although you can really program this from the ground up, it’s easier to reuse existing work. The factory example sketch is written with the Mozzi Arduino Library. You may remember Mozzi coming up before in our SbarkFun post. The Mozzi system allows wave shapes, generators, envelopes and other objects to be created and routed within the Arduino sketch — and can get a lot from a small microcontroller.

MIDI debug tool:

In the video, I have two MIDI shields and a USB serial device strapped to a RedBoard for MIDI splitting and debug output.

The software it runs is available at GitHub…/MidiSplitter, which starts a software serial instance for the debug port and dumps select MIDI messages on it.

Here are the parts used to build the device. (OK, so I used a USB Explorer instead of an FTDI Basic. Use whatever works for you!)

MIDI bender

The MIDI filter box is a bit more involved, and the source can be found at GitHub…/ArduinoSynthMidiBender.

The firmware is written to allow me to update and change the behavior of the filter as needs arise. For instance, this project required me to add the split feature, where I can select a split point, octave shift all notes and relative octave shift the upper half.

The flexibility is achieved by creating an included class DeviceSettings that holds all the data regarding the current configuration of the filter. A file BenderPanel.cpp contains state machines that control the settings object, and that configures the look of the panel based on its state and current settings.

Here are the parts I used to build the MIDI bender, which lives in an enclosure cut with a Shapeoko 3.

If you have any thoughts on these projects or the cool new synth, please share them in the comments below.

Keep on making,

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Stent-testing smart robot makes the medical grade

via Raspberry Pi

The Raspberry Pi often makes the world a better place. This time, it’s helping to test 3D-printed stents using a smart stent-testing robot.

Stents are small tubes used to prop open a patient’s airway. They keep people alive, so it’s incredibly important they don’t fail.

In fact, the FDA (Food and Drug Administration) requires testing of each design by compressing it over 300,000 times. That’s a sturdy challenge for any human, which is why machines are normally used to mash up the stents.

The usual stent-destroying machines are dumb clamps, with no idea whether the stent is breaking or not.

Stent Testing Robot Camera

A smarter stent-testing robot

Enter the Stent-Testing Robot, an intelligent arm that mashes stents while a Raspberry Pi Camera Module keeps a sharp eye on how it performs.

It’s designed by Henry J. Feldman, Chief Information Architect at Harvard Medical Faculty Physicians.

“We start with a CT scan of the lungs, and via a 3D reconstruction get the size and shape of the bronchus that we wish to stent open,” explains Henry. “The trick is to make it the exact shape of the airway.”

The challenge with testing is if stents start to fail before the end of the test. The dumb devices currently used continue to pulverise the stent when this happens.

Stent Testing Robot Camera Squisher

Machine vision to control stent-testing

The Raspberry Pi, meanwhile, uses machine vision to stop the mashing at the moment of failure.

The instant-stop approach enables Henry’s team to check which part failed, and view a time-lapse leading up to the failure. The video helps them design more reliable stents in the future.

Henry explains:

Naturally, we turned to the Raspberry Pi, since, along with a servo control HAT, it gave us easy OpenCV integration along with the ability to control a Hitec HS-5665MH servo. We also added an Adafruit 16-channel Servo/PWM HAT. The servo controls a ServoCity Parallel Gripper A.

Python was used to write the servo controller application. The program fires off a separate OpenCV thread to process each image.

Henry and his medical team trained the machine learning system to spot failing stents, and outlined the likely points of failure with a black marker.

Each time the gripper released, the robot took a picture with the Pi Camera Module and performed recognition of the coloured circles via OpenCV. If the black marker had a split or was no longer visible, the robot halted its test.

The test was successful:

While the OpenCV could occasionally get fooled, it was remarkably accurate, and given this was done on an academic budget, the Raspberry Pi gave us high-performance multi-core capabilities for very little money.

The post Stent-testing smart robot makes the medical grade appeared first on Raspberry Pi.

Ultrasonic Transducers – measurements and horn design

via Dangerous Prototypes

Lindsay Wilson writes:

Over the past few years, I keep getting inquiries from people asking about how to measure the resonant frequency of these transducers, how to design horns, tune the length etc. I decided it was time to do a video about the entire process – hopefully I’ve covered everything relevant. If you check the YouTube description, I’ve put time links to each individual section of the video.

Project info at imajeenyus.com.

TwoPotatoe and ThreePotatoe compete at AVC

via Pololu Blog

I am happy to bring some overdue attention to our customer who created TwoPotatoe, a balancing robot that I first wrote about on this blog a few years ago. This past fall, TwoPotatoe and his new robot ThreePotatoe competed in the Sparkfun AVC Competition. TwoPotatoe won first place for the 10 lb to 25 lb weight class. Check out the AVC video below! TwoPotatoe starts its run at about 53:00. ThreePotatoe won second place in the 25 lb to 40 lb weight class. Considering all the weight classes together, TwoPotatoe and ThreePotatoe scored third and fourth place overall, which is very impressive considering they were competing against four-wheeled robots that didn’t have to balance. ThreePotatoe’s run starts at about 1:08:30.

You can find more pictures and information about TwoPotatoe and ThreePotatoe in the AVC competition on the TwoPotatoe website.

GoonieBox: a puzzling piece of interactive furniture

via Pololu Blog

Customer Guido Bonelli Jr., who is also the creator of the Dr.Duino Arduino shield, had us laser cut pieces of baltic birch for a unique piece of furniture for his home: a large, interactive puzzle. An Arduino Mega 2560 R3 controls the various puzzles and contraptions packed into this piece. His article in Design News goes into more detail including a parts list and more pictures.

Thanks, Othermill!

via SparkFun Electronics Blog Posts

Sometimes when you’re working hard and fast to accomplish the ridiculous, you tend to fly right past some of the smaller, but certainly no less important, steps of a build. Such was the case here recently, while milling some prototype boards on our Othermill Pro.

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Our Othermill Pro - So much more than just a PCB mill!

In our haste to get one of our new boards milled so that we could test it, we neglected to offset the board file from zero when we sent it to the Mill. The result was that, when it cut out the board, it also took a nice bite out of our alignment bracket.

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Rookie mistake.

We got in touch with support over at Other Machine Co, and they were amazing! Not only did they send us two replacement alignment brackets (maybe we sounded like we might make the same mistake at least once more?), but having heard us mention a high frequency noise, they suspected it might be a power supply issue, and sent out a new one of those as well.

It’s always great to find solid tools to make your job - and your life - easier. But when those tools are backed up by an equally solid company with a great support staff, well that’s just the powdered sugar on the beignet!

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