Electrical Engineering Department
BS in Electrical Engineering
“Development of an Audio-Triggered EL Wire Sequencer” California Polytechnic State University 2011, Ben Paik and John Oliver, Ph.D. (advisor)
The purpose of this project is to investigate and develop a method for switching electroluminescent wire (EL wire) such that it can be activated by some audio source. EL wire is essentially a coaxial capacitor that luminesces when an alternating electric field excites the insulating phosphor layer in the wire (a 100Vp, 1kHz AC source is sufficient for this). The system involves the EL wire, a six channel sequencer to switch the EL wire, an method for processing the audio signal, and a microcontroller to interface these subsystems.
The user selects from two modes of operation – one where each EL wire is associated with a certain frequency, triggering when a magnitude threshold is crossed and the other where each wire is associated with a magnitude threshold for a selected frequency. Both the threshold and frequency in each respective mode can be selected.
Optoisolator TRAICs were initially tested as EL wire switches but failed due to their inability to handle 160Vp from the AC driver; normal TRIACs were used instead. Similarly, FFT implementation was abandoned due to lack of memory on the ATMega32A microcontroller and the low sampling rate of the ADC. The MSGEQ7, a seven-band graphic equalizer display filter was used instead to process the audio input. Free RTOS was used in the software design to achieve the response time necessary for real-time operation.
Final implementation of the design was successful, with expected functionality and a response time under 51ms.