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Aquatic Spectrometer & Turbidity Meter. Preliminary Design Review ECE 4007 L1, Group 8 Paul Johnson Daniel Lundy John Reese Asad Hashim. Introduction & Background. What is it? A device to detect the colour and clarity of a uniform flowing water sample

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Aquatic spectrometer turbidity meter

Aquatic Spectrometer & Turbidity Meter

Preliminary Design Review

ECE 4007 L1, Group 8

Paul Johnson

Daniel Lundy

John Reese

Asad Hashim


Introduction background
Introduction & Background

  • What is it?A device to detect the colour and clarity of a uniform flowing water sample

  • How will it work?LED’s, 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



Electronic specifications
Electronic Specifications

  • LED’s (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



Optics prism
Optics - Prism

  • Higher cost

  • Larger area required

Source:http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/prism.html


Optics diffraction grating
Optics – Diffraction Grating

  • Inexpensive

  • Easily positioned

  • 500 grooves/mm

  • Resolution of 0.633nm

Source:http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/gratcal.html


Optics physical placement
Optics – Physical Placement

  • Requires fine sensor adjustment

  • +/-0.1mm tolerance for 1st order maxima

  • Active sensor area is the limiting factor


Mechanical hardware
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




Base support plate
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


Vertical support plate
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


Cmos mount plate
CMOS Mount Plate

Attaches the CMOS Sensor to the plate via standoffs

Provides the vertical alignment adjustment


Single board computer
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

Source:http://www.embeddedarm.com/Manuals/ts-7250-manual-rev2.2.pdf



Photo sensor interfacing
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 d[0] and three synchronization pins: d[1],vsync, and hsync

Source: Kodak KAC-9630 data sheet


Normalizing the spectrum
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


Color analysis obtaining spectrum values
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


Spectrum division
Spectrum Division

Visual representation of spectral division


Turbidity analysis
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



Conclusions
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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