Plasma Speaker Jordan Colburn-ECE Shawn Day-ME Paul Faget-ECE Phillip Shepard-ME Seth Tucker-ECE

Overview  Stand alone system  All necessary external connections are compatible with common consumer devices  Custom Power supply  RCA I/O  Intended for collaborative operation with external speakers  Plasma Speaker handles highs, external woofers handle lows

Overview - Block Diagram

Overview - Operation  Signal is input to Signal Processor  Signal broken up into high and low frequency components  High frequency converted to PWM, amplified and sent to Plasma Generator  Low frequency output at signal level  Power input to Power Supply  Provides 12V at low current, 67Vdc at high current  Plasma Generator uses HV transformer to create high voltages for electrodes

System Requirements  Needs to accept consumer level audio (2V p-p)  Must output filtered consumer level audio to an external system (2V p-p, low pass)  Must output high fidelity high frequency sound though a plasma channel  System must be able to power itself from a standard AC wall plug

Detailed Design – Signal Processor

 Filter  Adjustable volume  Adjustable low pass (<1kHz-∞)  Uses MCP604 Op-Amp ICs

Detailed Design – Signal Processor  Pulse Width Modulator  Uses Tl494 Motor Control IC to generate PWM signal  PWM is single sided, so audio signal is biased 0V [1]

Detailed Design – Signal Processor  Amplifier  Uses 2 FETs in parallel to distribute load  FETs are in parallel to each other, but in series with the load PWM In Load 67Vdc

Detailed Design – Power Supply

 12 Vdc  COTS Wall-Wart  35 Vdc  Uses 1:5 step-down transformer  Full-wave bridge rectifier give 35Vdc  6.8 mF Smoothing Capacitor provides smooth DC current

Detailed Design – Plasma Generator

 Switching transformer boosts input to tens of kV  Electrode assembly adjusts to allow optimal gap sizing

Test Results – Sound Output COTS tweeter Plasma Speaker

Test Results – Audio Signal Output All pass 1kHz Cutoff

Test Results – Power Supply  Multi-meter testing confirms operational integrity under specified conditions  Care must be taken to prevent system from overstressing power supply or itself  No built in safeguards

Conclusions and Recommendations  Optimization  Better HV transformer would allow for higher PWM carrier frequency  Improve signal circuitry design to help eliminate unwanted distortion  Safety  Implement more fuses  Use safe connectors  Current limiting  Research and Development  Explore arc behavior  Singing Tesla Coil

References  [1] TI’s guide to Designing switching regulators with the Tl494 IC. Available at: focus.ti.com/lit/an/slva001d/slva001d.pdf focus.ti.com/lit/an/slva001d/slva001d.pdf