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Wireless Network of Dissolved Oxygen (DO) Monitors

Sd-May11-20 Betty Nguyen Scott Mertz David Hansen Ashley Polkinghorn. Wireless Network of Dissolved Oxygen (DO) Monitors. Advisors Joseph Shinar Ruth Shinar with Bob Mayer. Background. Existing Solution Network communication confirmed, prototype No confirmed DO content measurement

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Wireless Network of Dissolved Oxygen (DO) Monitors

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  1. Sd-May11-20 Betty Nguyen Scott Mertz David Hansen Ashley Polkinghorn Wireless Network of Dissolved Oxygen (DO) Monitors Advisors Joseph Shinar Ruth Shinar with Bob Mayer

  2. Background • Existing Solution • Network communication confirmed, prototype • No confirmed DO content measurement • Bulky Code • No Calibration Messages • Power consumption ~180mA at all times • Non-functional boards • Faulty boards that would burn out

  3. Project Objective • Implement robust low-power, star topology network of DO sensors • Increase accuracy of DO measurements by factoring in temperature • Implement remote calibration of DO sensors • Reduce power consumption of units to increase battery life of remote sensors • Redesign and refactor existing implementation to increase maintainability and flexibility

  4. Functional Requirements • The monitor units shall take readings of dissolved oxygen and of temperature and use them to calculate DO levels. • The monitor units shall wirelessly transmit their readings to the master controller. • The master controller shall request readings from each monitor unit. • The master controller’s graphical user interface shall display information from each monitor unit to the user and allow an operator to obtain data from a specific unit. • The master controller user interface shall allow the user to poll a monitor unit for data. • The Windows service shall log all data processed through the unit in a SQL database. • The network nodes shall create a star-like topology. • The Windows service shall send calibration data to each monitor unit. • The monitor units shall enter a low-power sleep mode when not in use.

  5. Nonfunctional Requirements • The monitor units’ calibration data shall persist across power loss. • The DO monitors and the network coordinator must communicate when they are up to 1000 meters apart. • The system should be able to configure in a star topology. • The temperature measurements shall be accurate to ±1 degree Celsius. • The DO measurements shall be accurate to ±0.5 ppm. • The monitor units’ batteries shall last 14 days.

  6. System Decomposition

  7. DO Sensor Hardware

  8. DO Sensor Theory of Operation • Platinum/Palladium Octaethylporphyrin (Pt/PdOEP) films excited by UV or green OLEDs. • Measure DO by observing the decay constant (tau) of the photoluminescence (PL) of the excited PtOEP films

  9. DO Sensor Theory of Operation • Excite the PtOEP film • Sample PL over time using a photodiode and microprocessor to measure the voltage from the sensor • Calculate tau using least-squares exponential fit • 0% DO - ~100µs • 20% DO (air) - ~30µs • 100% - <5µs • Calculate DO with temperature (and film) dependent a and b

  10. DO Monitor Software

  11. ZigBee Node

  12. ZigBee Network Coordinator

  13. Master Controller Improvements • Modular Message Types • Fewer Database Queries • Separation of Concerns • Calibration Capability • Database Relationships

  14. Master Controller Service

  15. Master Controller GUI

  16. Master Controller Database

  17. DO Sensor Testing • Couldn’t compare DO measurement directly due to old, degradatedPtOEP films • Instead, measure tau and compared to lab measurement • 100% PL decay too fast to measure with MCU • Temperature measurements within ±1°C

  18. DO Monitor Unit Power Usage • Estimated battery life w/out changes (remote, 5 minute period): 2.4 days • Estimated battery life w/ changes (remote, 5 minute period): 20.2 days • Estimated battery life w/ changes (remote, 15 minute period): 23.7 days

  19. ZigBee Network Testing • Verified ZigBee Node can register with the Master Controller • Verified ZigBee Node can sleep and wake up • Verified ZigBee Node checks in periodically • Verified ZigBee Node can wake up the DO Monitor to get DO Data and for calibration • Verified the Network Coordinator can receive/send messages and interact with the Master Controller

  20. Master Controller Testing • Verified that message are scheduled correctly • Verified that the correct data is displayed • Verified that the correct data is exported • Verified MC Service’s response to node check-ins • Verified that readings from nodes are received and stored properly

  21. System Testing • Accurate DO and temperature readings transmitted to the Master Controller and logged • Calibration data transmitted to the DO monitor unit • Monitors use as little power as possible • Calibration and readings are scheduled and executed on remote devices • Readings are retrieved for export and display in the GUI • Network functioned correctly with simulated high traffic (Increased check-in rate on network of 3 nodes)

  22. What is Next for the Project • Integrate Pressure Sensor • Handshaking protocol for PC software and Network Coordinator • Switch from Zigbit Amp to Digimesh to allow for true mesh network with power saving • Reduce current usage to ~5mA in sleep mode • Create Network Coordinator PCB • Accurate readings at high DO levels

  23. Conclusions • Integrated temperature sensor • Brought current consumption down to ~40mA by using a sleep mode procedure • Actually measured DO content accurately • Upgraded and refined hardware • Created a working star network • Added calibration utility • Documented new and existing code

  24. Questions?

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