College of Engineering Unit:
The plasma speaker project aims to develop a functional Bluetooth speaker by creating and controlling plasma produced by a high voltage electrical arc. This technology has been demonstrated to be capable of producing speakers with excellent replication of high-frequency audio. Plasma speakers eliminate the mechanical problems of a traditional solid-diaphragm speaker because no physical material is used to create the pressure waves. The system functions by creating an electrical arc between two high voltage electrodes and modulating the AC signal so that the plasma oscillates is response to the magnetic field. The plasma also modulates the surrounding ionized air and creates pressure (sound) waves. The system works by taking in the analog audio signal via Bluetooth, and creating a pulse width modulation (PWM) signal using an FPGA, with the duty cycle corresponding to the input. This PWM signal is stepped up to 30V using high power switching MOSFETs and this 30V signal is sent through a flyback transformer. The transformer steps up the voltage by a 1:800 ratio, creating a high enough voltage potential to create an arc between the output electrodes. This high voltage oscillating arc replicates the input audio. Helium gas was also used in the system by injecting it below the electrodes, making it easier for the surrounding air to ionize and creating higher fidelity audio. The goal of the project is to produce an appealing, safe, and easy-to-use desktop size Bluetooth plasma speaker. Due to the dangers of high voltage, safety is a top priority and thus is reflected in many of our engineering requirements. This is fulfilled by many electrical and mechanical safety mechanisms designed into the system. The high voltage also creates specific design constraints and styles for the electronics of the system such a minimizing power dissipation and isolating noise. The project resulted in a working prototype of the plasma speaker and was successful in fulfilling our original goal.