John Park’s Workshop Project Videos

Here’s a handy playlist of my Adafruit project video series:

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Euroshield adds Arduino + Teensy to Eurorack Modular Synthesizer

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I’ve been diving into the world of Eurorack format modular synthesizers for a little while now. A terrific, fun, and versatile addition to my rack has been the euroshield 1 by 1010music, a module that brings Arduino and Teensy to Eurorack.

One of the things that attracted me to the Eurorack format is the terrific blend of analog and digital synthesis, control, and processing going on. As I put together my first small rack of equipment — a VCO (voltage controlled oscillator) for generating pitched audible-rate waveforms, VCA (voltage controlled amplifier), envelope generator, filter, and LFO (low frequency oscillator), I started to yearn for a way to inject other modulations, effects, and signal processing experimentally, without necessarily committing to the cost and size of more individual modules. The euroshield does just that.
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I met Aaron Higgins at a modular event at Perfect Circuit Audio while he was in beta stages with the euroshield, and he kindly offered for me to test one out and give feedback. I added the euroshield to my rack, plugged in a Teensy 3.2, and installed the latest Teensyduino and excellent PJRC Teensy Audio Library, and the 1010music Euroshield example files.

The euroshield and Teensy are powered by the 5V supply line inside the rack. The demo code let me fire up the four LEDs on the module, test the two trim pots and pushbutton to make sure everything was working. Then, its onto the good stuff — software defined module building! I created low pass filters, bit crushers, saw waves, LFO signals, arpeggios and note sequences, and more to interact over the signal inputs and outputs with the rest of my modules.
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The euroshield (or a Teensy + Audio Shield) really shines when you start using the Audio System Design Tool for Teensy Audio Library https://www.pjrc.com/teensy/gui/ which is a visual node-graph GUI for designing audio signal processing code. I had a lot of fun going through the tutorials from the Microcontroller Audio Workshop.
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Then, I started cooking up my own bits of code to do things like generate semi-random sequences (turn the knobs to adjust the randomness and note ranges). I used the euroshield with a Teensy 3.6 as a class compliant USB MIDI host to send clock signals to an Arturia Beatstep, my modules, a Pocket Operator drum machine, and other MIDI devices.

I also made a little reverb unit out of it. A friend of mine, Jim Bumgardner, is also using a euroshield in his rack, and wrote a very nice Turing Machine to generate random melodies that are pitch quantized.
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Before I got the euroshield I had been experimenting with using a Circuit Playground Express and a Metro M0 with my Eurorack, which also have lots of promise for interfacing with synthesizers, particularly using CircuitPython. My solutions for interfacing these currently involve a lot of alligator clip wires, so I’m very impressed at how nice and neat the euroshield is for tying together all of the wiring and circuits needed to have a microcontroller play nicely with -10V to +10V Eurorack control voltages.
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If you’re into Eurorack and microcontrollers, have a look at the 1010music euroshield.

Restoring an original Gameboy

I got this launch edition 1989 Nintendo Gameboy at a yard sale for $1 and decided to restore it and clean it up. First, I needed to re-solder the battery connectors to the PCB so it would start up. Then, I cleaned out the cartridge slot so it would actually load games. The yellowing on the case was pretty gnarly, so I took it fully apart and used the hydrogen peroxide + UV light method to reverse the ageing. It worked great!

The basic chemistry of it, as detailed in the retr0bright project page, is that there was bromine added to the ABS plastic to act as a fire retardant. Over time and exposure to UV light, the bromine finds its way to the surface, lending the yellow cast. Hydrogen Peroxide, and activator, and more UV light finish the job and allow the bromine to fly free, leaving the surface of the ABS entirely.

Here you can see the front of the case after ageing for 29 years next to the back of the case after the hydrogen peroxide + sunlight for six hours treatment.

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You can search for the exact method and different recipes online, but you essentially need a high-ish concentration hydrogen peroxide — here I’ve got 20 volume which is 6% concentration — and an activator such as Oxy and something to thicken it. People call this Retr0brite. It turns out that salon-grade hair “bleach” has all of the necessary ingredients rolled into one bottle.IMG_1171

Paint it on (after cleaning the case with water and rubbing alcohol and more water), seal it up in cling wrap, and put it in the sun for six hours.IMG_1173IMG_1174IMG_1175IMG_1200IMG_1202

What a difference!

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Here, I’ve gotten the top half going. I didn’t leave it in the sun for as long and may give it another shot to further remove the yellowing.

Air!

My workshop has been sweltering hot in the summer, Southern California weather being what it is. But now I’ve got air conditioning! Coming soon: roof insulation.

Standing Desk Build

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I designed and built this lovely standing desk a few months ago — these are the build photos.

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My materials of choice were galvanized pipe, SpeedRail and Kee Klamp connectors, four heavy-duty locking casters, and a maple butcher block top.

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I use it for my computer workstation in my workshop — it’s nice to be able to roll it around when needed. It would also make for a very nice workbench or kitchen prep table.

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The top is 48″ x 30″ x 1-3/4″ thick. The legs are 34-1/2″ tall, so including casters and butcher block top, it stands at 38″ high.

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Making Handbalancing Canes

Here’s a quick DIY for making handbalancing canes. My daughter and I built these in an afternoon. They’re great for working on handstands, press-ups, L-sits, dips, and handbalancing tricks. We use them during aerial straps classes at Cirque School LA, so I thought it would be fun to make a set at home.

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Parts:
-One 2’x’2′ piece of 3/4″ plywood (we started with pine, but that was too soft) cut down to three sections
-Two 4″ lengths of 2×4 for hand blocks (I used some scrap framing pulled from our 1939 house during a renovation)
-Four 3/4″ floor flanges
-Two 18″ sections of threaded 3/4″ black pipe (you can choose 12″ for a shorter stand, and can always swap them out later)
-Twelve #10 1-1/2″ screws
-Sixteen #10 3/4″ screws

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CNC Circuit Playground Holder

I decided I needed a Circuit Playground and Circuit Playground Express render farm. Here’s the stand I made on the CNC machine.

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I designed it in Fusion 360 and then milled it with the Othermill Pro.cpFarm_IMG_2511 First, I ran a pocket clearing pass.

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Next, I ran a pencil pass to clear out the scooped out slots for the curvature of the boards.
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These rough passes left behind a bit of material, as you can see here.
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The final cleanup was a parallel pass with a fairly tight stepover, I ran it at 90 degrees from the stock, so it followed the grooves and had longer runs.
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Here it is with a Circuit Playground Express nestled in it lovingly.

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Here you’ll see some purple prototype boards, and the new red Circuit Playground Classic Digi-Key will be selling as part of the “buy one , give one” donation program for Girls Who Code
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Here’s the full set, ready for various tutorials I’m working on with MakeCode, Arduino, and Circuit Python!
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