This simple circuit uses 5 leds, a switch and a battery, all soldered in place.
The wire looks great, and the circuit held up fine during a day of wear.
Machine-knitted lace circuit board. Components soldered by hand onto finished textile. The circuit creates a heart-beat-like pulse on the LED.
(Materials: silk, wire, capacitors, resistors, transistor, LED, 9v battery)
I'm developing a method to machine knit and solder copper wire, resulting in a flexible and conductive textile. Here are some of my test swatches, all knitted on my Brother 940 knitting machine in my new studio space. The swatches are knitted with 3 strands of 34 AWG wire, held together as a single strand.
I'm showing work in the "Concealed Carry" show at Experimental Station this month.
The show is a response to the new Firearm Conceal Carry law that went into effect January 1.
My work, "Security Blanket", features a knitted image of a gun, embedded with conductive fibers. Touching the trigger "triggers" a (very loud) audio recording of a gun shot. The piece uses capacitive sensing with an Arduino, and I'm excited to be working with this technology, as my students have expressed interest in it, and I plan to introduce a unit in my class on it soon.
The show opening is tonight from 5-8pm. Experimental Station is located at 6100 S. Blackstone Ave, at the edge of the Univ of Chicago campus.
The exhibit will be accompanied by two public conversations on the new law, led by former Chicago Public Radio host Steve Edwards.
[ETA 6/4/14 Here is a video of several speakers in action, taken at a speaker-making workshop I led in March.]
This speaker consists of four pieces of magnet wire, glued between two pieces of paper, positioned precisely over a magnet from a hard drive. The 4 pieces of wire are soldered together at both ends so that they carry audio signal from a small amplifier in parallel. The wires are placed just over the mid-section of the magnet.
This creates an effective speaker because hard drive magnets are dipolar. The broad face of the magnet has both a north and south pole. (Most bar magnets have just one pole per side, and aren't as effective for a flat speaker design.) Additionally, hard drive magnets are extremely strong.
When the wire is placed directly over the boundary between the magnet's two poles (i.e. the red line on the paper rests on the red line on the magnet), it produces a clearly audible speaker.
How and Why It Works
Electric current running through a copper wire produces an
electromagnetic field. If this wire is placed in a magnetic field, it experiences physical force.
The directions of the current, the magnetic field, and the physical force are all perpendicular to each other. A good way to remember this is Fleming’s left-hand rule, which uses your left hand as a mnemonic.
The thumb, forefinger, and middle finger are held perpendicular to each other, forming an x, y, and z axis. The first finger is the magnetic field (B), flowing from north (knuckles) to south (the fingertip). The middle finger is the electric current (I) traveling from positive (the knuckles) to negative (the fingertip). The thumb is the physical force (F), the direction the wire moves.
You can see this principle at work in a conventional speaker:
image: Tony DiMauro
The middle piece is the north pole, and the outer ring is the south. So the magnetic fields run perpendicular through the coil, with the result that it pushes out, in the direction of the cone. Very efficient!
Flattening the Speaker
A coil is great for speakers, but not particularly flat, as it sticks out perpendicular to the resonator.
So I started with a straight length of wire, glued between two pieces of paper. I centered it between the two very powerful poles on the face of the hard drive magnet. I attached a resonator, the paper, so the wire
vibrates the resonator, which vibrates the air much better than a piece of
wire. The result is an audible speaker. (The wire-between-two-magnetic-poles will look familiar to those who know the work of sound artist Alvin Lucier.)
However, one piece of wire doesn’t move the paper very much. To increase the volume, I attached several pieces
of wire, glued parallel to each other across the paper. I also sent the current running through the wires in
parallel (this is very important for increasing volume). Now all the wires vibrate the paper in sync.
My development of this design is on-going, and I am currently refining my knitting machine fabrication techniques. Stay tuned for more documentation.
Hannah Perner-Wilson's Kobakant - resource for e-textiles
Jess Rowland - foil-and-paper speakers using parallel wiring
Dr. Dominique Cheenne - my Columbia College colleague who suggested I look at planar speakers as an alternative model for embedded speakers
LaFolia Loudspeaker Project - a site for diy planar speakers
If you're ever in Central Florida, this place is worth a visit. A lot of junk from NASA, due to the location-- when I was kid, they had a used spacesuit hanging in a corner. It's long gone, but the buckets of electronics covering every inch remain.
I'm in Orlando for the holidays, so Saturday I decided to check out the local makerspace, FamiLab. Met some great makers who showed me the space and some awesome projects. Also learned that FamiLab stands for Four A.M. Lab, not Family-Lab. Big difference!
Playing around with the clamshell stompbox, I used two sketches included in the Arduino examples to turn it into a functioning switch.
To make a momentary push-button switch, I used the sketch, “IfStatementConditional”, found in the “Control” examples.
This sketch was meant for a potentiometer, so I treated the clamshell stompbox as one half of the potentiometer, and used a fixed resistor for the other half.