Mechanical Tide: automating kinetic sculpture

Last fall the University of Chicago contacted me about my kinetic sculpture, Mechanical Tide. The piece had entertained visitors in the lobby of the Physics Department since 2008 but they were renovating the building and now it needed to find a new home. So we arranged for them to move the work to Pumping Station: One, where I could give the piece a tune-up and cleaning, before sending it off to its next venue.

The piece arrived in January and I was delighted to find that the movers hired to pack and transport the work from U of C were quite familiar with it. One told me that he had done a number of moves for the school in the past, and would wait for appointments in the lobby where he could watch the piece run and enjoy the free Tootsie rolls put out for visitors. 

Once we had it unpacked, I got to work: resetting the controls, refinishing the wood, and a bit of tinkering to improve the ball movement. Much thanks to Joe Mertz, the creative fabricator behind Amalgam Incorporated, who lent his considerable expertise to the entire enterprise. 

The piece is meant to be viewed from above, a gently tilting table covered with ball bearings, continuously rolling back and forth. Underneath the sculpture is the automation: a hefty motor rotating an arm that lifts and lowers the table.

The speed of the table's movement is controlled by a potentiometer on the side of the white control box. The piece looks particularly cool when the movement is slowed down: the rolling of the balls is more gradual and staggered. But if it's turned down too low, the motor does not get enough electric current to start. There is an audible hum from the motor, but no movement. So the pot needs to be turned up a little (clockwise).

A custom built cam affixed to the motor's shaft, "tells" the piece what position the table is in. The cam, which has a notch in it, rotates as the motor raises or lowers the table. When the table is fully lowered, the notch triggers a microswitch. When it is raised, the notch triggers a second microswitch.

When the microswitches are triggered, they each send a message to a bright orange Ametek TMM timer and the timer's "1-shot" mode pauses the motor, for a programmable number of seconds.

A motion detector (disconnected in the photos) turns the piece on when it detects passers-by. This conserves energy when no one is present. The length of time it remains on is selected by a switch on top.


We'll be moving the piece to a new venue, very soon. Stay tuned!

Merry Circuits


I taught my classes how to make custom pcb in KiCAD this fall. One of my students, Dom Frugoli, ended the semester with PCB holiday cards (complete with silkscreen family portrait and Krampus).

Happy Holidays!



How do you grade a circuit board?

Photo: auto-wah circuit by Izaak Thompson

When I first started assigning circuit board projects, I couldn't find much material online about how to grade a circuit board, so I devised my own rubric.

I found the quality of student work improved significantly once they had the Build Checklist and could see how it was weighted in the grade.

The photo: my student Izaak Thompson devised and completed this circuit for his auto wah pedal project in my advanced Building Circuits class in 2020. Since the class was entirely online due to the pandemic, students had to submit photos and video of their assignments. It was an advanced class so all of them had previously taken the pre-requisite electronics class in-person before the pandemic started; I think that experience prepared them to do this course at home.

On a side note, the pandemic is how I discovered that one can troubleshoot circuits surprisingly well just by looking at photos-- the hardest part is making sure the photos are well lit!




Artist Talk at Waubonsee Community College

Photo Credits: Tonya Whitlock

I recently visited Waubonsee Community College to give a talk to Debra Kayes Halpern's Design students, sharing some of my knitted circuitry and discussing my sculpture installed at the college. Waubonsee had invited me to do a hands-on workshop with the students but the course was in an art room without any electronics tools so I couldn't introduce them to the joy of soldering or breadboarding.  Instead, we made Throwies, a brilliantly simple form of electronic graffiti invented by the Graffiti Research Lab at Eyebeam.

Throwies require zero tools and minimal materials. Tape the LED to the battery, then tape on a rare earth magnet. Find a public space with metal infrastructure (a bridge? building pipes?) and toss your Throwie till it sticks. We tossed our around in a black box theater on campus.

***Fun fact: the LED doesn't need the standard protection resistor in this circuit because the coin cell battery's internal resistance prevents it from delivering enough current to damage the LED.

Student Projects from AUDI 413 Building Circuits

For Columbia students, there's still a few seats available for this fall's class. We are waiving the AUDI 313 pre-requisite. If you've taken AUDI 104 or have electronics experience, that's enough. (Just email me if you want to register.)

These videos are from the Fall 2020 section

You can find a bunch more students projects, from different semesters, on my youtube channel.

Class is online this fall but there will be the option of weekly In-Person workshop time.









Two books featuring my work

Foundations in Sound Design for Embedded Media, edited by Michael Filimowicz.

I contributed Chapter 2: The Electronics of Microphones and Loudspeakers. This allowed me to revisit in-depth the technical material I was exploring when I did my textile loudspeakers. The book features the work of 25 authors, with far more impressive biographies than my own. I'm enjoying reading their contributions on the subject.

Fabric and Fiber Inventions by STEAM educator Kathy Ceceri. I'm thrilled to be featured as a "Fabric Inventor" on pg 116-117. 

New electronics courses at Columbia College Chicago

This year I've been busy managing the explosive growth of Columbia's Electronics-For-Audio curriculum. What started as a single elective course is now a 3-course sequence! 

The Audio Department's little electronics workshop previously served about two dozen students a semester. This spring, we had almost a hundred! We hired several new adjunct faculty, and an incredible team of teaching assistants who helped me keep 8 sections running smoothly. It's clear that we're outgrowing our current digs, so I'm also working out plans for some serious upgrades for the coming year. Change is afoot!

photos: Phil Dembinski

Here's the new lineup:

AUDI 104: Audio Electronics (pictured) The first, intro-level course, Audio Electronics, is now a part of the required "core" course sequence for majors. Students build stuff from scratch, like this loudspeaker from a plastic cup. They also build circuits using Snap Circuit kits, which are great for small group activities. (This is what's happening in the photographs.)

AUDI 313: Building Circuits for Modular Synthesis with Logic Gates After completing Audio Electronics, students can follow up with this elective on building circuits for analog synthesis. We build a number of projects from Nic Collins' book, Handmade Electronic Music. (I'm still kinda working on the course name for this one. I think I overdid it when the college said "More descriptive course names, please". )

AUDI 413: Building Circuits with Pick-Ups and Pedals This advanced class focuses on op-amps and pickups. It also fulfills a senior course requirement. Since students take the introductory class as a pre-requisite, they'll be able to get a lot further, a lot faster, in these two follow-up classes. 

The videos feature my Spring 2018 advanced students, in an improvised performance at Columbia's Manifest Urban Arts Festival this past May. I'm so proud! They built most of the hardware themselves: springboard instruments (inspired by Eric Leonardson), contact mics, spring reverb units, fuzz pedals and pitch trackers. Plus, checkout Rachael's "squarinet"-- that's a square clarinet-- that she built for her Physics of Musical Instruments course with Professor Dave Dolak.

Student Performers: Rachael Cowell, Vito Di Beasi, Hunter Funk, Aaron Gelblat-Bronson, Mac Kelley, Derek Muhl, Nick Novak, Isaiah Quino, Sky Roessler, Daniel Vega


Hola, SIGGRAPH! or How to do an e-textiles workshop for 50 people

I was invited to give a workshop with my knitted sensors on August 2nd at SIGGRAPH 2017, a huge computer graphics conference in Los Angeles.  It went great-- everyone's knitted sensors were up and running in just over an hour! 

Hands-on workshops require a lot of planning. People progress at different rates and can get impatient waiting for each other or for assistance. Too much waiting and the workshop loses momentum.  

So I like to work with small groups. I move around to offer assistance, and encourage people to help themselves to materials and progress at their own rate.

This wasn't going to work at SIGGRAPH-- the classroom was spread out with no middle aisle. And I'd be wearing a body mic. If I walked in front of the speakers, I'd set off ear-piercing feedback (which I did, twice, oops...). Plus... I wanted to give people sleeves that fit their hands but there was no way to measure hand sizes of participants ahead of time.

So we had to get creative with solutions.


Dylan responds to a post-it note call for help.

There wasn't room for participants to get their own materials, and asking for help would slow the presentation down. So I gave everyone bright yellow post-it notes. If they needed something, they wrote it on the post-it, attached it to top of their computer monitor, and one of our volunteers would sprint over to read the note and help or retrieve materials.  Worked great!


Ziploc full of goodies

Materials were distributed to each workstation in baggies, in advance, thanks to workshop coordinator Brittany Ransom. Plus, we put a pdf of the powerpoint presentation on each computer's desktop (see below). I invited people to use it to progress at their own rate.
 

Sewing diagrams

I tested out the activity with the volunteers ahead of time, and realized that tech people were going to struggle with sewing the wires in place. They needed sewing diagrams! Luckily I had time to add a few. We didn't have to worry too much about the knot because we had Fraycheck-- a fabric glue. And glue makes sewing seem easy!

I also made diagrams on Fritzing for the breadboard connections--super helpful.

Fits like a glove

Instead of sizing participants, everyone randomly received either a 10x30 or 12x40 size-sleeve on it (with the size labelled). I figured this would get the right size into the hands of at least half the attendees. I invited people to swap with their neighbors or flag us down to request another size. (I also brought 10x40 and 12x50 sized sleeves.) I was surprised to find that only a few people requested another size.

The one thing we didn't pass out in advance was the resistors. In order to get the best range from your sensor, it's important to match it with an appropriate fixed resistor. But the resistance of the sleeve depends on how it fits the wearer.  So I had everyone measure their sleeve resistance and write it on a post-it. The volunteers picked up the post-its, and passed out appropriate resistors.

In preparation, I had taped the resistor packs onto a large cardboard backing with the values labelled. During the workshop, it was easy for the volunteers to grab the exact resistor they needed to "fill the order" on each post-it.

 
Materials for Knitted Finger Sleeves
Resistive yarn (80% polyester, 20% stainless steel)
Snaps #199 10 Line (6.9 mm), nickel finish
Striveday silicone coated stranded wire AWG 26
Male crimp pins  these are great for breadboarding
tapestry needle
yarn for sewing wire
Dritz Fraycheck

Also used:
Breadboards
Hookup wire
Arduino uno
piezo discs
resistors
multimeters
scissors

My tools (used to knit the sleeves ahead of time and attach wire with snaps)
Superba Knitting Machine
Snap Press Machine (with punch/die)
Crimp tool (I use Engineer Inc PA-09 crimping pliers )

img: Tesia Kosmalski


Improving Arduino sensor range



Adding a fixed resistor ½ the value of a variable resistance sensor improves Arduino performance.


Whenever you connect a 2-lead variable resistor (VR) sensor (like a photo cell or bend sensor) to an Arduino, you add a resistor to it. I did this with my knitted stretch sensor. It creates a circuit known as a voltage divider, which controls the voltage level, based on the relative resistance of the resistor to the sensor. This is important because the voltage level is what AnalogRead "reads" in Arduino.


I wondered what value would give the best performance for my knitted sensors. So I used the equation below to calculate the output range of voltage dividers, based on the ratio between R1 and R2, given that R2 is my knitted sensor and R1 is the (unchanging) resistor. I graphed the outputs for each VR value at 0%, 25%, 50%, 75%, and 100% of its maximum range.

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