15-01-2013, 12:01 PM
Laser Communicator
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Introduction
•Idea:
–Encode a signal onto a beam of light with a microphone.
–Read this signal some distance away
•Potential Use: Surreptitious line-of-sight communication through glass or vacuum.
•Components:
–Microphone
–Laser
–Op-amps
–Photo Detector
–Speaker
The Microphone Amplifying Circuit
•This circuit amplifies Vinand it gives it a specific offset equal to Voffset.
•Section 1: High pass filter that removes the natural offset of a signal
•Section 2: Resistors set gain for the signal
Laser
•Vinis the output from the microphone.
•Laser brightness is proportional to current
•Current is proportional to voltage, as shown by the equation V=IR
Speaker Buffer Circuit
•This circuit amplifies signal from the gain step and provides current for the speaker.
•Section 1: Removes extra noise from Vin
•Section 2: Provides the needed amount of current to drive the speaker
Conclusion
Challenges
•Finding the right level of gain and offset so that the laser signal is powerful but not too powerful for the laser detector
•Laser alignment
•Gaining up the signal enough to hear it