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Laser Microphone

Laser Microphone. CDR. Edward Nicholson Kareem Nammari Wes Stanway Kari Skupa Cui Sun. Recap. Measures vibrations resulting from sound waves. Designed for covert surveillance but has other uses. Edward. Problems. Lab access Need sponsorship Optics Alignment Expensive Lasers

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Laser Microphone

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  1. Laser Microphone CDR Edward Nicholson • Kareem Nammari • Wes Stanway Kari Skupa Cui Sun

  2. Recap • Measures vibrations resulting from sound waves. • Designed for covert surveillance but has other uses. Edward

  3. Problems • Lab access • Need sponsorship • Optics • Alignment • Expensive • Lasers • Safety Edward

  4. Accomplishments • Basic photodiode • Viewed a distorted version of original signal • Working sound box • Aquarium with speakers • A/D Converter • Confirmed capability • Stores digital signal Edward

  5. Low Goals • Basic bounce at an angle configuration • Replay Signal • Basic Filtering Edward

  6. Medium Goals • Identify audio source through DSP (FFT) • Store audio signal • Terminal Control Edward

  7. High Goals • Interferometry configuration • LCD Display • FFT signal analysis directly on board • Wireless signal communication Edward

  8. Software Functional Decomp LEDs USB Microprocessor I/O Intel x86 Embedded Software Software A/D Converter Hardware Interrupts ADC Read Matlab Hardware Buttons Hard Memory Audio Out Edward

  9. Hardware Functional Decomp Interferometer Laser Detector Analog Filters A/D Converter Microprocessor Optics Selector / Mux Memory Software Audio Amplifier Audio Source Audio Out I/O USB Hardware Post Processing POWER Terminal Laser! ±15 V Matlab +3.3V Sun

  10. Power Wall Wart • 12 V DC • 1-2 A Sun

  11. 3.3VRail • Powers the microprocessor • Can be powered by either USB or Wall wart • RS232RL chip Sun

  12. ± 10V Rail • MUX • OpAmps Sun

  13. LaserDriver • Adjustable intensity • Power the laser Sun

  14. Optics • Interferometery is on the backburner. • Focusing on Bounce System • Mounting • Rail • Board • Tripods Kareem

  15. Filters • All Filters are Active • Bessel Filters • Maximally flat group delay • All filters are second order • Antialiasing Filter • 4th order Butterworth • Very sharp cutoff • Phase delay not particularly important Kareem

  16. 7KHz LPF Kareem

  17. 20KHz LPF Kareem

  18. 60Hz HPF Kareem

  19. AA Filter Kareem

  20. Op-Amps • Op-Amps are LMP7704 • Low Noise • Wide Supply Range • High Bandwidth • Quad Package • 14 Pin SOIC Narrow Kareem

  21. Detector • Using a BPW21R photodiode for bounce • Detects light between 450nm and 700nm • Detection speed is not particularly important • No need to bias the photodiode • Sensitivity is increased when photodiode is unbiased • Gain can be adjusted easily Kareem

  22. Wes

  23. Wes

  24. Wes

  25. Wes

  26. MCU: MSP430F5438 • LCD capability • 20 MHz clock speed • 256 kB of flash memory • 16 kB of SRAM • 12-bit ADC • 87 GPIO pins Kari

  27. ADCSampling • Able to sample at 44,100 Hz • Can read amplitude of a signal • Can store amplitude data on chip Kari

  28. SoftwareInterface • Post-processing in MATLAB • DSP and FFT • Terminal communication • I/O interface • 8 LEDs • 3 buttons • USB • Audio jack out Kari

  29. DivisionofLabor Kari

  30. Budget Kari

  31. Schedule Kari

  32. MilestoneGoals Milestone I • Populated board • Basic analog reading • Tested power supplies Milestone II • Revised board layout • Populated the revised board • Working prototype Kari

  33. ExpoGoals • LCD display • Data storage • On-box options • Fourier analysis • Filter selection • Output on display Kari

  34. QUESTIONS?

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