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LASER MICROPHONE

EDWARD NICHOLSONKAREEM NAMMARI

WES STANWAYKARI SKUPA

CUI SUN

CDR

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– Safety

EDWARD

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

LOW GOALS

•Basic bounce at an angle configuration•Replay Signal•Basic Filtering

EDWARD

MEDIUM GOALS

• Identify audio source through DSP (FFT)• Store audio signal• Terminal Control

EDWARD

HIGH GOALS

• Interferometry configuration• LCD Display• FFT signal analysis directly on board• Wireless signal communication

EDWARD

SOFTWARE FUNCTIONAL DECOMP

Intel x86

Software

Microprocessor

Embedded Software

Matlab

I/O

Hard Memory

HardwareButtons

USB

LEDs

A/D Converter

Audio Out

ADC Read

Hardware Interrupts

EDWARD

POST PROCESSING

INTERFEROMETER

DETECTOR

ANALOG FILTERS

AUDIO AMPLIFIER

A/D CONVERT

ER

MICROPROCESSOR

AUDIO OUT

SOFTWARE

I/O

MATLAB

SELECTOR / MUX

AUDIO SOURCE

POWER

LASER

OPTICS

TERMINAL

HARDWAREUSB

MEMORY

LASER!

±15 V

+3.3V

HARDWARE FUNCTIONAL DECOMP

SUN

POWER

Wall Wart• 12 V DC• 1-2 A

SUN

3.3V RAIL

• Powers the microprocessor• Can be powered by either USB or Wall

wart• RS232RL chip

SUN

± 10V RAIL

• MUX• OpAmps

SUN

LASER DRIVER

• Adjustable intensity• Power the laser

SUN

OPTICS

• Interferometery is on the backburner.• Focusing on Bounce System• Mounting

– Rail– Board– Tripods

KAREEM

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

7KHZ LPF

KAREEM

20KHZ LPF

KAREEM

60HZ HPF

KAREEM

AA FILTER

KAREEM

OP-AMPS

• Op-Amps are LMP7704– Low Noise– Wide Supply Range– High Bandwidth– Quad Package

• 14 Pin SOIC Narrow

KAREEM

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

WES

WES

WES

WES

MCU: MSP430F5438

• LCD capability• 20 MHz clock speed• 256 kB of flash memory• 16 kB of SRAM• 12-bit ADC• 87 GPIO pins

KARI

ADC SAMPLING

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

KARI

SOFTWARE INTERFACE

• Post-processing in MATLAB– DSP and FFT

• Terminal communication• I/O interface

– 8 LEDs– 3 buttons– USB– Audio jack out

KARI

DIVISION OF LABOR

Kari Sun Cole Wes Kareem

Software Power Software Layout Optics

Digital Hardware

Optics Digital Hardware

Power AnalogHardware

Sound Box Analog Hardware

Sound Box Populate Board

Detector

Optics PopulateBoard

Populate Board

Full Schematic Budget

KARI

BUDGETBlock Estimated Cost

Laser $50

Optics $250

PCBs $120

Digital Components

$150

Analog Components

$200

Power $100

Demo Box $75

Expo Materials $75

UROP Funding -$1000

Total -$80

KARI

SCHEDULE

KARI

MILESTONE GOALS

Milestone I• Populated board• Basic analog reading• Tested power supplies

Milestone II• Revised board layout• Populated the revised board• Working prototype

KARI

EXPO GOALS

• LCD display• Data storage• On-box options

– Fourier analysis– Filter selection– Output on display

KARI

QUESTIONS?