~ICMC 2015 - Sept. 25 - Oct. 1, 2015 - CEMI, University of North Texas
of the earth and its atmosphere [2]. Elements of the Tesla coil
design also made their way into commercial products and its
circuitry is fundamental to radio transmission [3]. Contemporary usage of Tesla coils generally centers around entertainment, with science museums and other venues around the
world utilizing them to provide spectacular lighting shows.
2.1 Tesla coil use in music
A musical Tesla coil, which may also be referred to as a
singing Tesla coil, Zeusaphone, or Thoramin is a solid state
Tesla coil (SSTC) which is able to use its arc to produce
melodies via external control. The practicality of enabling
Tesla coils to produce musical notes coincided with the rising attainability of insulated-gate bipolar transistors (IGBTs),
which are capable of switching high voltages and extremely
high currents, (up to thousands of Amps) for brief periods
and at radio frequencies. Though it was possible to generate
steady tones with early SSTCs and even older vacuum tube
designs, electronic melodic playback was achieved around
the year 2000 by Richie Burnett with a small scale coil with
a short arc [4]. In 2005 Joe DiPrima and Steve Ward built a
larger scale dual resonant type SSTC which was able to create melodies via larger, more impressive arcs, and they delivered the first public performance using musical Tesla coils in
March 2006 [5]. Soon afterwards, Scott Coppersmith developed the first true MIDI-based control system [5] followed
closely by a video created by Steve Conner in June 2006
which brought widespread awareness of the technique [6].
Steve Ward and Joe DiPrima's musical Tesla coil project
would later form the basis of the ArcAttack group which has
toured extensively. Other artists that have made use of musical Tesla coils include Bjirk with her piece entitled 'Thunderbolt' and the Tesla Orchestra [7].
2.2 Musical Telsa Coil Controllers
There are several musical Tesla coil controllers (also called
interrupters) available as commercial products, kits, and built
for personal use. Examples of commercial products include
the Eastern Voltage Universal Handheld MIDI Interrupter, the
ClassicTesla MIDI Pro Tesla Coil Controller and the oneTesla
MIDI Interrupter. These all receive MIDI data and send corresponding pulse information to the coil in order to generate
notes. These units are predominantly monophonic with some
options offering duophony, allowing two notes to be played
by a single coil simultaneously, but lack any expressive parameters beyond pitch-bend control. Blake Johnston's 'Nico'
controller improved on several of these limitations allowing
4-note polyphony, individual velocity control over each of the
voices, and providing the option to send control messages via
OSC as well as the usual MIDI [8].
3. CHIME RED
A new musical Tesla coil controller named Chime Red was
built by James McVay and Josh Bailey and seeks to provide
composers and performers with advanced expressive musical
control over Tesla coil performances.
Figure 2. The front panel of the Chime Red enclosure.
3.1 Hardware
The front panel of the Chime Red box shown in Figure 2 features a key to arm the unit, a 16x2 character LCD display,
LED indicators, and several knobs and toggle buttons. From
left to right, the buttons toggle between MIDI and PCM input modes, external and internal signal generation, fixed or
variable pulse-width, full or limited maximum level, and acceptance of channel 10 MIDI information. In MIDI performance mode, the lower knobs control the maximum pulserate, maximum pulse-width and maximum voltage input parameters. This allows the system to be adjusted to the size
and power handling capability of the coil being controlled.
The controller's software computes the correct pulse length
and relative timing within these maximums according to the
requirements of the musician. In the offline signal generator
mode, the momentary fire button on the top right enables the
output, while the knobs control frequency and pulse length.
Currently the MIDI and signal generator modes have been
implemented, with the PCM input mode under development.
The rear panel shown in Figure 3 is equipped with a 9V DC
power supply socket, a USB socket for USB-MIDI communication and firmware updates, and MIDI In and Thru sockets.
To minimize interference on the transmission lines, the signal to the coil is output by way of a fibre transmitter. These
pulses control the gate of the IGBT in the coil which controls when power is input. TTL compatible BNC ports provide PCM TTL input, as well as outputs for gate diagnostics,
charge enable, and charge level. The charge outputs allow the
controller to control both when power is input and the instantaneous input voltage. This feature enables advanced musical
features for coil designs that require a fixed pulse size like
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