Home Chapter 4 Artist's applications of capacitance
Artist's applications of capacitance
Chapter 4


The fact that capacitance can be measured and used as input has been exploited in various kinds of experimental musical instruments, such as Todd Machover’s Sensor Chair. The artist Liz Phillips has also used capacitance to modulate sound in her sculptural environments.

The sensor chair utilizes RF-field (radio field) capacitive sensing in order to sense the body movement of the user. Metal sensors are located in plastic canisters both above and below the user. These sensors measure the varying electrical field around the user and by moving to different positions and speeds this data is taken and translated by software and this determines the weight and levels of activation that different movements will or will not be activated by the software as well as which movements will produce which sound.

 

Sensor Chair by Tod Machover , in collaboration with Joe Paradiso, 2004

 

In discussing his work Todd Machover says: The trick is that we have to be very clever about what aspect of the body movement to measure (you don't want to collect all the data--which would be too much, and not very interesting--but just the relevant data) to indicate what "feeling" the movement has and how to define which movements will produce what music.

 

Liz Phillips creates soundscapes that are activated by the movement of the audience/participant(s) by interrupting electronic signals that activate synthesizers.

In discussing her work she says: I make my work a lot like a painter paints with a wide palette. You mix a little of this and a little of that until you build up the right textures of background and foreground. A lot of what I'm trying to achieve is a dynamic variation that's very much like landscape – like the wind would carve sand dunes.

 

Sunspots by Liz Phillips, 1982. Sunspots is a site-specific sound installation that is tuned to the room in which it's heard. Audience presence and nearness to a copper coiled arch and suspended brass screen determine the combination of sounds.

 

Selecting Capacitors:

Like most parts, select capacitors that best meet the need for your project.

When using electronic parts you must be concerned with absolute maximum ratings. These ratings are the maximum quantities of voltage, amperage,and frequency that a part can withstand and if these maximums are exceeded, then damage to your part is probable.

When selecting capacitors, the key characteristics to be concerned with are value, working voltage, dielectric, class, size, tolerance, and whether or not the capacitor is polarized.

Value is the amount of µF in the capacitor, and you can join capacitors to create custom amounts of µf or microfarads.

Working voltage is the maximum voltage allowed. When choosing a capacitor for a project that calls for a 35v capacitor, it is wise to over-design and use a 50v capacitor.

Larger capacitors can store a lethal charge, and great care should be taken when handling these devices.

A friend told me a story about how he accidentally discharged a large capacitor from the back of a TUBE based TV he was deconstructing, and he woke up across the room.

The capacitor had discharged into his body and his leg muscles contracted like a frog. He is lucky to be alive. Handle large capacitors with care.