Laser Communication Science Fair Projects

Lasers

Lasers used to be a thing of science fiction. Today they are used for everything from toys to weaponry.

Bioloid Beginner Programmable Robot	OWI-9762 WAO Kranius Robot	Snap Circuits Wireless	LG8547 LEGO Mindstorms NXT 2.0 Robotic Invention System
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Objectives/Goals

Laser communication has many advantages over wired devices. Lasers can carry messages near the speed of light with little interference whereas electrical signals travel at 60%-90% of speed of light. The goal of my project was to build a low cost device to transmit my voice a long distance in open air using lasers and learn as much as I can about the related technologies.

Methods/Materials

I researched, brainstormed, and conducted a series of experiments in 2007 through Feb'08 to understand the concepts and built devices for sending my voice in open air using lasers.I video taped diaphragms of speakers playing sounds, examining the motion frame-by-frame, and learned the basics of speakers, sound, waves, frequency, microphones, lasers, solar cells, Doppler effect, simple circuits, and analysis /computer tools.

In my first series of experiments, I connected small mirrors to speakers and eventually headphones. I shone laser beams onto mirrors while playing music. I pointed the reflected beams into solar cells connected to MIC input of a laptop and used Adobe SoundBooth to capture and analyze the received signals.

In my second set of experiments, I used carbon-dust microphone to modulate my voice onto laser beams. I built my own carbon-dust microphone from pencil led (which I learned from a Nova science program on telephones). I connected the carbon microphone in series with the laser pointer batteries. I shone the beam onto a solar cell 200 feet away connected to the MIC input of a laptop, and captured /amplified the AC signal generated by variations in laser photon intensity.

In my final set of experiments, I attached a mirror to the bottom of coffee cans and shone lasers onto the mirror while talking into coffee cans. I pointed the reflected beams onto a solar cell connected to MIC input of a laptop.

Results

I achieved my goals of building a device capable of transmitting my voice with great clarity for $32 and learn many new concepts in the process. The carbon MIC had medium sound quality and cost $24. The coffee can designs cost $21 with 30% of transmitted words recognizable.

Conclusions/Discussion

Audio signals can be transmitted long distances using the techniques in my experiment. I also discovered other practical uses of my experiments including recreation of audio signals using lasers reflected off of vibrating windows acting as diaphragms far away, detecting earthquakes, and ground movements. 3rd party contributor