Musical Jacket with embroidered keypad.

The Musical Jacket (Figure 3) turns an ordinary
denim jacket into a wearable musical instrument,
allowing the wearer to play notes, chords, rhythms,
and accompaniment using any instrument available in
the General MIDI scheme. It integrates directly into
the jacket an embroidered fabric keypad, a MIDI
sequencer/synthesizer, amplifying speakers, a fabric
bus sewn from conductive organza, and batteries to power
the above subsystems.

The embroidered keypad is flexible, durable, and
highly responsive to touch. It was mass-produced us-
ing ordinary embroidery techniques and a mildly con-
ductive stainless steel and polyester composite thread
(Bekaert BK50/2, described later), and demonstrated
for the first time that a textile keypad could be made
by e-broidery on a single layer of fabric in one step.
This process allowed us to precisely specify the cir-
cuit layout and stitch pattern in a computer-aided
design (CAD) environment, from which any number
of articles can be sewn under machine control.

The MIDI jacket keypad used a PIC** microcontroller
from Microchip Technology Inc., to perform capac-
itive measurements of connections to sewn elec-
trodes on a denim substrate. The measurement was
implemented almost entirely in software as an ex-
ercise in developing electric field sensors with a min-
imum of hardware, but this minimalism also bene-
fits the fabric circuit designer by reducing the number
of components (and hence interconnections) re-
quired in a circuit. The electrode array was sewn in
the pattern of a telephone keypad, with traces lead-
ing from the symbols to an array of connection pads
intended to mate with a conventional circuit board.

The resistivity of the electrodes and their associated
connecting traces is reduced by the precise place-
ment of individual stitches. Each electrode is sewn
from a single continuous thread that crosses itself
many times, leading to a multiplicity of intersections
that create parallel resistances and increase the over-
all conductivity of the sewn circuit element. By us-
ing this “e-broidery stitch” we obtain resistances per
unit trace length that are dramatically lower (by more
than an order of magnitude) and more consistent
than those obtained with conventional embroidery
stitches (e.g., satin or tatami stitches) that are cho-
sen for their appearance or texture.

The embroidered keypad 3 uses a capacitive sensing
technique 4 because of the high impedance of the
sewn electrodes. The measurement algorithm is sim-
ilar to that used in the Museum of Modern Art
(MoMA) table described elsewhere in this issue, 5 but
here the measured capacitance is compared to a
threshold to distinguish contact events. This mea-
surement is implemented using a single bidirectional
digital input/output (I/O) pin per electrode and a
leakage resistor (which can be sewn in highly resis-
tive yarn). Key contact events are output as a serial
data stream by the microcontroller. The circuit board
makes contact with the electrodes at the circular pads
only at the bottom of the electrode pattern. A view
of the component side of the circuit board has been
superimposed to show its extent and its connections
to the fabric. A flexible circuit board can be substi-
tuted for the rigid one used in this implementation.

Fifty denim jackets were embroidered with this pat-
tern and outfitted with sewn fabric buses that carry
power, ground, serial data and analog audio signals
across the backs of the jackets. These jackets also
provided an AC ground for the keypad, to ensure con-
sistent capacitance measurements. In all 50 jackets,
both the fabric keypad and bus worked reliably and
held up to repeated mechanical stresses better than
the more traditional wires and connectors also used.
The interface between the sewn keypad and the elec-
tronics led into our work to do away with the circuit
board entirely.

Figure 3: On the left is the Musical Jacket, comprising a fabric keypad on one side, a MIDI synthesizer “boat” on the other side, speakers behind speaker grills in the pockets, and fabric buses visible inside the jacket. On the right is a composite image of both sides of the circuit board attached to the back of the fabric keypad.


BM SYSTEMS JOURNAL, VOL 39, NOS 3&4, 2000 POST ET AL. 843

OK. What on earth is it? Where are the pics? Is there a link to take a look?

I have no idea what this is supposed to be.

Pic please.

Oh No...all that means is that Prince is gonna be playing a girlfriend.

Well why isn't this shit locked yet?