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OXYBUOYConstructing a Real-Time

Inexpensive Hypoxia Monitoring Platform

Rizal Mohd NorMikhail NesterenkoPeter Lavrentyev

ASIT 2009

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Hypoxia Description

Hypoxia – dissolved oxygen depletion in the lower part of the water column

an emerging global problem negatively affects biological resources: fish and commercial

invertebrate species anthropogenic causes

hypoxia dimensions - affects a large areas in coastal waters over the summer

up to 20,000 km2, up to 50 meters in depth, 10-40 miles off shore active up to 4 months

poorly understood – no accurate models to describe phenomenon, needs empirical measurements

measurements techniques research vessels – vessels can be sent to collect water

samples or trawl sensors expensive and insufficient data density

satellite images no biological markers does not occur at surface

unattended sensor buoys

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Why Build a New Buoy

commercial offerings market too small – tend to make them generic

and expensive

COTS components enable scientific multi-parameter sensors to construct buoys

we propose Oxybouy inexpensive COTS components easy to assemble allows long term deployment

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Outline

Oxybuoy description components component cost architecture programming and operation electric power design

experiments lab experiment Bath lake deployment power consumption study

future work

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Oxybuoy Components

processor Gumstix embedded computer

Xscale PXA270 processor PIC16F86 Microcontroller

Nalresearch 9601-D-N satellite modem via RS232 ZebraNet D-Opto DO sensor via SDI-12

more robust than membrane based DO sensor Vegetronix RS232 to SDI-12 converter 802.11(b and g) wireless card Dimension Engineering 5V 1A switching voltage regulator 2 Gig Flash Micro SD card 12 volts 7Ahr seal acid battery

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Component Cost

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Oxybuoy Architecture

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Gumstix Programming and Operation

data sampling receive power level from the PIC processor sample DO sensor requests satellite modem to transmit the data

data transmission and saving checks the signal strength indicator. If it is too low, the data is saved to flash card and

transmitted next time check for change in sampling rate request from data center

system power down send command to PIC to set sleep interval check WiFi for connection, remain awake if exists send power down signal to PIC

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Electric Power Design

managed by PIC

two operating modes active sampling mode:

draws 350 mA turns on for every sampling period has 1024-bit ADC connection to the battery to read voltage level PIC operation

sends the current battery voltage level to the Gumstix waits for a 2-bit signal from Gumstix to indicate the sleep

duration when signal received, switches to sleep mode (power down

the remainder of the system)

power saving sleep mode: draws 11 mA only PIC remains powered PIC operation

keeps track of the clock cycle for the next sampling time turns system on for the active sampling mode

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Lab Experiment

Objective: test the operation of the electronics in controlled environment

used a water tank in a fish physiology laboratory at the AkronU equipped for hypoxia experiments

DO concentration in the tank was maintained at specific level tank had external thermometer and YSI DO meter minimal protective packaging for the electronic components only the DO sensor was submerged configured Oxybuoy to use the wireless card to report the measurements every

20 minutes to the wireless bridge and on to the data center located at KSU

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Lab Experiment Results, Temperature

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Lab Experiment Results, DO

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Bath Lake Deployment

Objective: test the complete operation of Oxybuoy in target environment

deployed buoy in Bath Lake, a small eutrophuc lake within the Bath Nature Preserve near Akron, Ohio for 7 days

did not use power saving mode

during the deployment, Oxybuoy reported DO measurements 6 times per hour

Oxybuoy remained operational and reported data for over 18 hours

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Bath Lake Results, Temperature

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Bath Lake Results, DO

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Power Consumption Study

Objective: to estimate the lifetime of the buoy in multi-mode operation ran the electronics of the buoy in the

simulated deployment electronics were configured to switch to

data acquisition mode once an hour PIC recorded battery power output and

relayed it to Gumstix stopped experiment when battery

power > 8 Volts (required by the DO operation)

results: Oxybuoy produced 155 samples.

For four 4 months operation required battery:

1 hour duty cycle, 160 Ah battery 6 hour duty cycle , 28 Ah battery

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Conclusion and Future Work

demonstrated Oxybuoy viability

plan on building extended prototypes and array of buoys

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OXYBUOYConstructing a Real-Time

Inexpensive Hypoxia Monitoring Platform

Rizal Mohd NorMikhail NesterenkoPeter Lavrentyev

ASIT 2009

Thank you!Questions?