Tie And Jeans

Archive for the tag “scratch”

Violins and Voltage Dividers

This is a quick project sketch, building on a conversation with Josh Burker. It’s a reference, not a tutorial.

This is probably possible using the MakeyMakey’s analog input ports, but the Picoboard’s resistance sensors are a better and more direct choice.

This was my first prototype. Apologies for the sideways video.

This just uses a few resistors in series along a span of copper tape. After checking that the values were distinct enough, I had the Scratch instrument play the resistance value as the note. This is probably a bad plan for actual music. :)

Josh asked for a string that could be fingered to change pitch, while the “bow” played in the same place.

violin string

This is random wire, wrapped around popsicle sticks at either end of the cardboard tube and taped in place. The kinks and bends in the wire are no good, but the concept is sound.

I attached one clip form the Picoboard to the bow, and one to the copper tape + resistor strand. The key is that the wire/string doesn’t touch the copper tape at all. If you touch the bow to the string, you don’t complete the circuit.

In order to get any reading (ie, resistance less than 100 in Scratch), you need to pinch the string to the resistor+tape.

photo 2 (1)
You need a multimeter for this. The Adafruit Circuit Playground app would also be a helpful, between checking resistor codes and calculating the voltageOut.

Making this into a stable instrument is hard work. What voltage range can the PicoBoard sense? How do those values map to Scratch’s 0-100? How do those 0-100 values turn into pitch? What size resistor makes a good step? How many “frets” can you fit on the neck of your instrument? How close together do you fit the strings? Does fingering a chord produce a clean combination of tones or something else? Do you keep the fingers on your chord-ing hand electrically isolated? Does the bow need to be isolated?

Those aren’t facts to discover, but choices that will shape design. You could give that framework to 50 kids and wind up with an orchestra of different instruments.

photo 3

photo 2 (2)

photo 4


MakerEd update: Looms and Bridges

I dread Halloween for a number of reasons. The most trivial among them is that starts November and the traditional* post every day challenge. Working with that daily requirement forces me to realize how easily I fall into bad “essayist” habits with the blog. I don’t post about stuff until I’ve got something to say about the stuff, which in my saner moments I recognize is the exact opposite of the correct plan.

In the spirit of November, here’s the disjointed status of Makers.

The most elaborate Scratch+MakeyMakey project my class has ever seen reached something like alpha software and moved on to laying copper tape. Hence this, the most elaborate Bridges of Königsberg puzzle I’ve ever seen. I felt so math teacher proud about this. I laid down the law! Paths must not cross!

baseball bridges

There was a full period of pencil sketching on the inside of their contraption before they even thought to reach for copper tape. They worked smart, using the raised edges, and running a long common ground through easily two dozen triggers. Then, after so much had been laid down, they discovered that they had taped themselves into a corner. “Isn’t there some way we can put stuff between the layers of tape?” Yes. now is the time when we talk about insulators and conductors.

Nate Kellogg asked about how our MS kids are using the 3D printer. Up until this week, my honest answer would have been “not as much as I had hoped.” The kids who actually built the machine display some ownership over it’s continued functioning, but they don’t seem to have any interest in using it in a significant way. I wasn’t sick with grief over this, but it was a bit surprising to me. I was happy to see that when other projects needs some thing, the printer would get called in to service, which represents both a crucial skill set and a mind shift for middle school students. But… I thought all kids were crazy for small plastic trinkets!

This week, I found the small plastic trinkets for which our students bring the craze. Makers and gentlenerds, the Rainbow Loom.


Are rubber band bracelets a thing with your kids? Then these designs will drive incredible traffic to your printer.

We started out using this great SCAD design for a closed ring loom. The commercial kit uses linear strips of the pegs that mount onto a base in various configurations. It’s pretty flexible, but bulky and not well suited for designs that extend off of the loom itself. The circular loom we’ve been printing is perfect for those, and turns a design that’s a tricky mess on the normal setup (the HEXAFISH**) into something that’s super easy and compact.
There have been more 5th and 6th graders in the lab this week than ever before. I know the about the “whistle trap” for 3D printing (although I can’t remember who coined the phrase), where the device becomes a tool to make a certain thing rather than something that enables student design. In my head I pretend that the loom isn’t a whistle, in part because of the changes they’re making to the base design in OpenSCAD. But really, I’m willing to risk it because of the crazy velocity, the sheer churn of kids coming into the space and asking about what they can make.

In other groups we have a RC plane under construction, a bunch of 555 timer projects (bad move: starting kids with breadboard projects more complicated than a pushbutton LED), a skeeball game, and powered paper airplanes. But the other lesson I remember from previous Novembers is that it’s better to post half the story in an 20 minutes than try to cover everything in an hour.

* aka I’ve done it twice

**strictly speaking the N-Fishtail.

Artifact from a good day

Each 5th grade class had a moment today where the only sound was the chuffing of adolescent brains capturing their own absurd/hilarious pigeon visions on Scratch.

It made a horrible photo. Just kids sprawled out laptops. From the back it’s just a vendor ad. From their screen side, all you see is the rough, oddly zoomed Mo Willems inspired art. Nothing caught their perfect half smiles, tweaked just a bit by the challenge of translating their mental movie in a few move and costume blocks.

Makers was great, but similarly unphotogenic. I think that P- walked out with a Drawdio enabled tie. J- left this on the pinball machine, after a period checking coil resistances with the ohmmeter.


There was a small dance party when he found the line on the schematic between the blown 10amp fuse and coil #3, burned out with only 2ohms of resistance.

That moment would have made a good media artifact for the day. I missed it because I was too busy dancing.

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