Aquatic Spectrometer

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Aquatic Spectrometer Turbidity Meter

• Preliminary Design Review
• ECE 4007 L1, Group 8
• Paul Johnson
• Daniel Lundy
• John Reese
• Asad Hashim

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Introduction Background

• What is it?A device to detect the colour and
  clarity of a uniform flowing water sample
• How will it work?LEDs, a diffraction grating, a
  photodetector array and an on-board PC
• Why do we need it?Demand from Aqua-culturists
  and Water Regulation Authorities for a cheap and
  easy to use device

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High Level Block Diagram
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Electronic Specifications

• LEDs (Luxeon LXHL-NWG8)Switched on/off via
  control signal, through 350mA Continuous Power
  Supply
• CMOS Sensor (Kodak KAC-9630)Triggered to capture
  via control signal through serial interface
• Power Considerations

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Electronic Block Diagram
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Optics - Prism

• Higher cost
• Larger area required

Sourcehttp//hyperphysics.phy-astr.gsu.edu/hbase/
geoopt/prism.html
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Optics Diffraction Grating

• Inexpensive
• Easily positioned
• 500 grooves/mm
• Resolution of 0.633nm

Sourcehttp//hyperphysics.phy-astr.gsu.edu/hbase/
phyopt/gratcal.html
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Optics Physical Placement

• Requires fine sensor adjustment
• /-0.1mm tolerance for 1st order maxima
• Active sensor area is the limiting factor

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Mechanical Hardware

• Secure the optical and electronic components to
  the enclosure
• Facilitate and ease the alignment process
• Keep the system calibrated, mechanically, as long
  as possible

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Two Slits Assembly
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CMOS Sensor Assembly
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Base Support Plate

• Slotted holes provide movement and alignment
  adjustment for the distance between the
  diffraction grating and CMOS sensor
• Mates to the Vertical Support Plate

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Vertical Support Plate

• Three Point Precision Mount (Springs and Screws)
• Middle screw hole utilizes negative pressure via
  lock down screw to secure position
• Provides minute adjustments in the horizontal
  direction
• Mates to both the Base Support Plate and CMOS
  Mount Plate

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CMOS Mount Plate

• Attaches the CMOS Sensor to the plate via
  standoffs
• Provides the vertical alignment adjustment

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Single Board Computer

• TS-7250 ARM9 Single Board Computer
• 200 MHz
• 32 MB RAM
• Programming in C
• Four source files
• SpecMain.c
• SquareWave.c
• Process.c
• Networking.c
• Compiling with ARM9 compiler obtained from vendor
• Networking software with wireless networking
  capabilities

Sourcehttp//www.embeddedarm.com/Manuals/ts-7250-
manual-rev2.2.pdf
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Software Flow Chart
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Photo Sensor Interfacing

• Sensor will be clocked at 10 MHz
• A 1 byte intensity value corresponds to each
  pixel on the sensor
• A serial image consists of a data out pin d0
  and three synchronization pins d1,vsync, and
  hsync

Source Kodak KAC-9630 data sheet
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Normalizing the Spectrum

• The white light spectral response
• of the sensor is not perfectly flat
• Other factors such as LED spectral
• output also add distortion to white
• light response

• These inconsistencies are accounted for by
  performing spectral analysis with no sample
  present and multiplying the measured response of
  samples by the inverse of the white light
  response

Source Kodak KAC-9630 data sheet
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Color Analysis - Obtaining Spectrum Values

• Intensity values are stored in a vector
• Vector is divided into 3 (or more) regions
• Total intensity of each region is calculated
• The resulting regional intensities are compared
  to each other and stored as ratios
• Ratios are compared to predetermined ratios from
  known algae samples to determine the algae's
  growth stage

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Spectrum Division
Visual representation of spectral division
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Turbidity Analysis

• Regional intensities from color analysis are
  summed to create an overall intensity
• The weaker the overall spectral intensity, the
  greater the turbidity
• Intensity to turbidly conversion will be
  calibrated by finding the spectral intensities of
  various samples of water with known turbidities

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Cost Analysis
Part Cost
LEDs 9
SBC 184
CMOS Image Sensor 14
Optics Kit 10
Power Supply 20
Misc. Hardware 120
Total 357
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Conclusions

• ElectronicsSchematics drawn, parts en route,
  prototyping in progress
• OpticsParts en route, calculation
  experimentation stage
• MechanicalMechanical drawings done, in
  fabrication stage.
• SoftwareSBC delivered, preprogramming stage

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Questions?