EL wire's construction consists of five major components. First is a solid-copper wire core coated with phosphor. A very fine wire or pair of wires is spiral-wound around the phosphor-coated copper core and then the outer
Indium tin oxide (ITO) conductive coating is evaporated on. This fine wire is electrically isolated from the copper core. Surrounding this "sandwich" of copper core, phosphor and fine copper wire is a clear
PVC sleeve. Finally, surrounding this thin and clear PVC sleeve is another clear, colored
translucent or
fluorescent PVC sleeve. An alternating current electric potential of approximately 90 to 120 volts at about 1000 Hz is applied between the copper core wire and the fine wire that surrounds the copper core. The wire can be modeled as a coaxial
capacitor with about 1 nF of capacitance per 30 cm, and the rapid charging and discharging of this capacitor excites the phosphor to emit light. The colors of light that can be produced efficiently by phosphors are limited, so many types of wire use an additional fluorescent organic dye in the clear PVC sleeve to produce the final result. These organic dyes produce colors like red and purple when excited by the blue-green light of the core. A resonant
oscillator is typically used to generate the high voltage drive signal. Because of the capacitance load of the EL wire, using an inductive (coiled)
transformer makes the driver a very efficient tuned
LC oscillator. The efficiency of EL wire is very high, and thus up to a hundred meters of EL wire can be driven by
AA batteries for several hours. In recent years, the LC circuit has been replaced for some applications with a single chip switched capacitor inverter IC such as the Supertex HV850; this can run 30 cm of angel hair wire at high efficiency, and is suitable for solar lanterns and safety applications. The other advantage of these chips is that the control signals can be derived from a microcontroller, so brightness and colour can be varied programmatically; this can be controlled by using external sensors that sense, for example, battery state, ambient temperature, or ambient light etc. EL wire - in common with other types of EL devices - does have limitations: at high frequency it dissipates a lot of heat, and that can lead to breakdown and loss of brightness over time. Because the wire is unshielded and typically operates at a relatively high voltage, EL wire can produce high-frequency interference (corresponding to the frequency of the oscillator) that can be picked up by sensitive audio equipment, such as guitar pickups. There is also a voltage limit: typical EL wire breaks down at around 180 volts peak-to-peak, so if using an unregulated transformer, back-to-back
zener diodes and series current-limiting resistors are essential. In addition, EL sheet and wire can sometimes be used as a touch sensor, since compressing the capacitor will change its value. ==Sequencers==