CLOUD BASED LASER MICROPHONE. GROUP ONE – Final Presentation Anirudh rawat |ali sultan | basil dixon | Bryant donato. OUTLINE. Summary Points Current Design For Completion Technical Overview Requirements Met & Missed Design Changes Usage Sequence Diagram Raw Data Future Considerations
CLOUD BASED LASER MICROPHONE GROUP ONE – Final Presentation Anirudh rawat |ali sultan | basil dixon | Bryant donato
OUTLINE • Summary Points • Current Design For Completion • Technical Overview • Requirements Met & Missed • Design Changes • Usage Sequence Diagram • Raw Data • Future Considerations • Demonstration Video
SUMMARY POINTS • After testing four different multiple circuit designs, we have assembled a working laser microphone combined with an audio amplifier that can pick up ambient conversations and music • Our prototype works at a distance 21 feet ( 7 yards) and is scalable to 10+ yards • We have developed a working linux software platform that has an automated script that works. • We have also expanded the design added a windows platform for ease of use and compatibility • We can pick up ambient music, audio, and background sounds off multiple reflective surfaces, including glass, mirrors, and windows.
TECHNICAL OVERVIEW • Our circuit uses a pre-packaged LM386 amplifier circuit which we customized to take input via a phototransistor. It is powered using a standard 9V battery, yielding over a day of battery life! • A phototransistor replaced a photodiode because it is much more sensitive to light, and allows us to pick up human voice with greater accuracy • We soldered everything to the most compact breadboard possible, measuring roughly 1.5 inches by 2.5 inches. • This was placed in a metallic project enclosure, that will act as a Faraday cage and ground to reduce interference (under certain conditions, we were able to pick up FM radio transmission and listen to 102 WVAQ). • An onboard potentiometer controls volume (amplification). • A standard 3.5 mm output jack allows a user to record audio to a computer or use headphones to listen to audio. • The design has changed very little from our original concept
DESIGN CHANGES • A prepackaged LM386 circuit was substituted for our hand-built circuit to guarantee quality, electromagnetic shielding, and robustness. The unit only added $7 to the cost of the project, which is negligible. • MATLAB added to software platform – filters and scripts • Windows added to software platform, along with audio processing software Audacity which allows for quick editing of .wav files • Note: Security is still a top concern, with SSH keys being required on the raspberry Pi • Database software not implemented due to lack of time. • Interferometer setup was abandonded for two reasons: • Project became too precise, bulky, and expensive. This was difficult to deploy quickly and easily in the field • Lack of time for implementation. A standard LM386 diode circuit worked just fine.
RAW DATA CAPTURED • Filtered: • Unfiltered: • We have successfully used filters in MATLAB, Audacity, and other signal processing software. • A combination of lowpass, highpass, and bandpass filters were used, but not thoroughly developed due to lack of time. • Commercial, off-the-shelf programs like audacity do a satisfactory job with default filters. • All of the programs were successful in removing various amounts of noise.
FUTURE CONSIDERATIONS LIMITATIONS • Project limitations remain unchanged • Stable surface without vibrations is required • The more ambient light present, the more noise will be introduced into recorded audio • A voltage delivery of at least 9 volts, (maximum 12 V) is required. Exceeding 9 volts is NOT recommended. Drill holes in project enclosure to display power on/off LED, and to allow for control of amplification potentiometer. (potentiometer is currently set at 50% volume). Provide some kind of light shade on acquisition phototransistor to reduce ambient light noise.