Exploratorium Exhibit 2010

new Solderless Breadboard Felting LED Flasher

This led flasher uses a conventional astable multivbrator (with LED's in the emitters) but unconventionally uses conductive felt for the mechanical and electrical connections and to form the resistors.

Laser Cutting Conductive Fabric

Most conductive and resistive fabrics can be easily cut with a laser.

Felting Electronics

Felting techniques illustrate how an inclinometer and rotary position sensor is constructed from conductive thread and resistive thread from Eeonyx.

Kalimba Controller with piezo-resistive fabric pressure sensor for displacement measurement

This simple controller is inspired by the south African kalimba. The kalimba lends itself to rapid assembly because of its use of a single central bar held down by two screws to trap the array of tines between two pivot points. Wooden tines are used in this prototype because they are faster to shape than the traditional metal and this controller doesn’t require the tines to be tuned. The flexibility of copper tape is exploited as strips follow the contour of the flat base around the curve of a half-round pressure pivot.

Orientation

Are you feeling Red, Green or Blue? Just orient this convex hexahedral cage to illumunate the color of your choice. The lights flicker when you bang the table it is on (presumably the ball in the tilt switch bounces).

Dual Multitouch Pad with pressure

This controller demonstrates how most resistive touch screen systems can be modified to provide independent sensing of two positions on the surface. A single pressure measurement is also provided with a third sensing layer. A pair of SlideWide sensors (http://infusionsystems.com) are stuck to each other at right angles.

Pressure Sensing Illuminated Button Array

Illuminated button array music controllers have a long history. I was fortunate to meet the late great, Salvatore Martirano who pioneered the construction of large button array music synthesizers.

Tablo: e-textile Fabric Drape Sensing Controller

This controller with no direct antecedents is made by draping conductive stretchable fabric over a cereal bowl creating a curve similar to the famous one called the witch [sic] of Agnesi. Resistive strips around the bowl are shorted out by the fabric and the varying resistances are measured and sent as OSC messages via USB control software on a host computer - typically resonance model sounds in Max/MSP.

The fabric is stretched in an embroidery hoop and draped over an inverted circular bowl. A piece of conductive plastic cut in a special shape forms a corolla on the surface of the bowl. The tips of each petal are folded inside the bowl and taped with conducting-adhesive copper tape or fabric tape. The microcontroller board measures the electrical resistances of these petals from their tip to a common center established with a gold-plated fabric ring at the flat of the bowl. As the conductive stretchable fabric (the “calyx” to complete the flower analogy) is displaced towards the bowl it shorts out different lengths of each conductive plastic petal.

The result is a circular array of nearly mass-less displacement sensors. The gesture-to-displacement relationship changes according to distance from the center of the bowl (variable “gearing)”. This allows for several different playing styles.

One style, similar to hand drum technique, involves tapping the fabric surface directly onto the bowl with the fingers of one hand and leaning towards the other side of the bowl with the palm. Another style involves both hands interacting from the outer hoop towards and around the base of the bowl.

You may also put it on the ground and use it as multiple foot “pedals”.

A second version increases the number of fabric pressure sensors on the base board from 2 to 16.

An important point about the Tablo is that the drape sensing allows both very delicate light touch to be sensed along with very muscular or fast gestures when the fabric touches the piezoelectric strips. It is very hard with stacked position and pressure sensors to achieve this dynamic range so essential for compelling hand drum gestures.

It has been designed so that all the important sensing nodes are surrounded by grounded fabric to keep the noise down.

The hoop is easily removed so that the only moving part (the stretch fabric) can be replaced or washed.

A single pressure sensor is snuck into the top of the bowl.

There is lots of interesting potential math behind the shape of the bowl: spherical doesn’t work well, a catenary may yield a nice linear relationship between the finger position and sensed value, the “found object” bowl used is very good and almost linear.

You can scale this design up to support multiple people playing it if you can afford the fabric.

You can also build it in a linear/keyboard style instead of "in the round".

Battery and Power Supplies you can Sew

A collection of power sources for e-textile and wearables projects.
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