Underwater LaserCommunication

P15252

Ethan Lavine - MEFrank Mekker - EETyler Montesi - CEPat Shuman - CE

Tariq Hashimi - EE

Agenda

● Recap/Problem Statement● Eng Requirements - Updated● Functional Decomp - Overview● Concept generation - Overview● Function Generation - Detailed per function● Concept Selection - Detailed per function● System/Test Rig design overview● Functional Architecture● Feasibility Analysis ● House of Quality/Risk Management● Project Plan● Questions

Problem Statement (Recap)

● Proof of concept for underwater uniaxial laser communication● high-speed● reliable● Faster data transfer than acoustic system● Alpha level project but many follow ups in the future (Biaxial

communication, etc.)

CN/ER - Updated

Functional Decomposition

Beginning of Concept Generation: Morphological Table

Function #1* - Align the Laser(Functional Decomp)

● Need to align laser to the receiver or receiver to the laser● Customer Need constrains us from having digital feedback for alignment● Visual feedback is necessary to insure proper alignment (LED)

Function #1: Align the Laser(Concept Selection)

Function #2- Input Command(Functional Decomp)

User → Input Device → Microcontroller → Laser

Function #2: Input Command(Concept Selection)

* Decision affected by Display Results PUGH chart

Function #3 - Send Data(Functional Decomp)

● Microcontroller provides digital signal to laser driver

● Laser driver modulates laser diode● ~450nm λ on EM spectrum is least

absorbed/scattered by water

Function #3: Send Data(Concept Selection)

Parameters Amplitude Modulation Serial

Ease of Implementation - +

Transfer Rates + -

Cost S S

Power Consumption S S

Function #4 - Receive Data(Functional Decomp)

● Customer Need constrains us to stationary receiver● Photoelectric sensor excited by photons of laser!

Photoelectric Requirement Analysis

Rise/Fall Time Responsivity (at ~450nm λ)

Reverse Bias Voltage

PN Photodiode 10ns - 400 ns .12 A/W <50 V

PIN Photodiode .1 ns - 5 ns .4 A/W < 50 V

Avalanche PD .1 ns - 2 ns 10-125 A/W 150-300 V

Phototransistor 1 us - 10 us 18 A/W (β) < 50 V

Photo-Multipliers <<1 ns 10^5 A/W > 500 V

Photoresistor 10 ms - 30 ms ----- < 50 V

Function #4: Receive Data(Concept Selection)

Function #5 - Display Command(Functional Decomp)

-Highly based on concept selection

Function #5: Display Results(Concept Selection)

Test Rig System Design

Test:Primary Function → Concept Selection

Align Laser → PVC Pipe

Input Command → Keyboard

Send Data → Serial Communication

Receive Data → Photodiode

Display Data → “Hello World”

Transmitter

PVC pipe

Receiver

Final Product System Design

Final:Align Laser → PVC

Input Command → Joystick

Send Data → Serial Communication

Receive Data → Photodiode

Display Data → Video Game

Transmitter

PVC pipe

Receiver

Functional Architecture

Q#1) How easy would it be to seal the container for the components?

Worst = + Poor = ++ Good = +++ Best = ++++

Feasibility Analysis 1

Parameters Latex Layer

Custom Rubber Seal Epoxy O-ring

Application Ease ++ + ++++ +++

Expense ++ + +++ ++++

Effectiveness + ++++ ++ +++

Allowance for Modularity ++ ++++ + +++

Feasibility Analysis 2Q#2) How many bits will be needed for a packet of data?

Assumptions: Using communication to play a 4-directional videogame(Pacman, pong,.. etc) with a joystick and a keyboard.

Analysis: 4 bits per direction for intensity of each direction 4 directions 4 bits for header (may need two) Results: 20 bits per packet = 4 bits per direction * 4 directions + 4 bits for header

Since we have a desired transfer rate of 15 kbps this would be our minimum baud rate

Feasibility Analysis 3Q#3) What are the bottlenecks for speed of each concept selected?

● The clock cycle of the micro-controller○ Baud rate of average microntroller supports up to 250 kbps○ Customer wants 15 kbps

● The excitation time of the receiver (resistance and capacitance of the photoreciever)○ Worst Case for photodiode is 500ns which supports up to 2MHz

● The propagation delay of the gates○ Average delay of a non inverted gaining Op-Amp is 2 ns meaning supports up 500

MHz● The stabilization rate of the laser (key constraint)

○ previous attempts by other projects have remained stable up to 100 kbps

Feasibility Analysis 4Q#4) How much power is needed for each circuit system selected?

Transmitter Supply Voltage Current (Max) Power

Driver/Laser 5V 1600 mA 8W

Microcontroller 5V 400 mA 2W

Reciever

Microcontroller 5V 400 mA 2 W

Schmitt Trigger 5V 24 mA .12 W

House of Quality

Risk Management

Project Plan

QUESTIONS?