Aquatic Spectrometer & Turbidity Meter

Preliminary Design Review

ECE 4007 L1, Group 8Paul JohnsonDaniel Lundy

John ReeseAsad Hashim

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

High Level Block Diagram

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

Electronic Block Diagram

Optics - Prism

Higher cost Larger area required

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

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 Requires fine

sensor adjustment +/-0.1mm

tolerance for 1st order maxima

Active sensor area is the limiting factor

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

Two Slits Assembly

CMOS Sensor Assembly

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 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

Attaches the CMOS Sensor to the plate via standoffs

Provides the vertical alignment adjustment

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

Software Flow Chart

BeginProgram

Compute turbidity

Set up Program

Store resultsDetermine colorTake in serial data

Turn LED's on andoff

SpecMain.c

SquareWave.c

Process.c

Networking.c

Establishconnection

Send data

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 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

Source: Kodak KAC-9630 data sheet

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

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

Visual representation of spectral division

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

Cost Analysis

Part CostLEDs $9

SBC $184

CMOS Image Sensor $14

Optics Kit $10

Power Supply $20

Misc. Hardware $120

Total $357

Conclusions Electronics

Schematics drawn, parts en route, prototyping in progress

OpticsParts en route, calculation & experimentation stage

MechanicalMechanical drawings done, in fabrication stage.

SoftwareSBC delivered, preprogramming stage

Questions?