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?