1 OXYBUOY Constructing a Real-Time Inexpensive Hypoxia Monitoring Platform Rizal Mohd Nor Mikhail Nesterenko Peter Lavrentyev ASIT 2009

2 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 km 2, up to 50 meters in depth, 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

3 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

4 Outline Oxybuoy description  components  component cost  architecture  programming and operation  electric power design experiments  lab experiment  Bath lake deployment  power consumption study future work

5 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 (b and g) wireless card Dimension Engineering 5V 1A switching voltage regulator 2 Gig Flash Micro SD card 12 volts 7Ahr seal acid battery

6 Component Cost

7 Oxybuoy Architecture

8 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

9 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

10 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

11 Lab Experiment Results, Temperature

12 Lab Experiment Results, DO

13 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

14 Bath Lake Results, Temperature

15 Bath Lake Results, DO

16 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

17 Conclusion and Future Work demonstrated Oxybuoy viability plan on building extended prototypes and array of buoys

18 OXYBUOY Constructing a Real-Time Inexpensive Hypoxia Monitoring Platform Rizal Mohd Nor Mikhail Nesterenko Peter Lavrentyev ASIT 2009 Thank you! Questions?

19 Oxybuoy Description Oxybuoy functions  measure DO concentration, temperature, voltage  record and manage data  manage power usage  facilitate satellite communication  interact with data center data center operation  sampled data are uploaded  data center communicate SAT operator server via Internet  gather data from multiple Oxybuoy data center architecture  LAMP  PHP scripts are written to process, save and visualize data in real-time  JpGraph for data presentation

20 Buoy Casing and Ballast casing  made out of 6’’ PVC pipe  housed electronics, ballast and the battery  buoy attached by chain to anchor  hermetically sealed with PVC glue for waterproofing  oxygen sensor and the satellite antenna cables were fed through the silicone-sealed hole in lid ballast calculation  computed the weight of the ballast to have the buoy ¾ submerged calculated based on buoyancy and displacement  measured the weight of the buoy along with the weight of the equipment to be installed  tested the ballast using weights  sandbags were used as weights necessary to fine tune the amount of required ballast  after getting the correct measurement for the ballast, replaced the sandbags with the exact amount of weight

21 Outline Gathering Data For Hypoxia Why Construct a New Buoy Challenges of Sensor Marine Design Oxybuoy Description  Oxybuoy Components  Component Cost  Oxybuoy Architecture  Gumstix Programming and Operation  Electric Power Design  Buoy Casing and Ballast Experiment Setup  Lab experiment  Bath Lake Deployment  Power Consumption Study Future Work

22 Experiments Setup lab experiments  tested sensor device in a controlled environment Bath lake deployment  tested in the lake for 7 days power consumption study  important to verify life-time of device

23 Power Consumption Study, Voltage This result agrees with the calculations.  battery is rated at 7 Ah  during the active sampling mode the average current draw of Oxybuoy is 350 mA.  takes about 6 minutes to sample the DO sensor and transmit the data.  allows 120 samples.  we are able to obtain more samples since we are able to use the battery until the voltage fell below 8 V. 4 months operation battery requirement estimate  1 hour duty cycle, 160 Ah battery  6 hour duty cycle, 28 Ah battery

24 Challenges of Marine Sensors Design harsh environment  hardware has to be robust  packaging have to withstand environment power limitation  not accessible to power cables  battery power may not last and changing batteries is cumbersome  solar panels are expensive communication  underwater communication requires acoustic modem short range, unreliable, high latency  IEEE requires high mast to communicate due to Fresnel Zone  satellite communication expensive for large data sets