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Senior Design SD1107 Solar Module Observation Device

Students: Collin Howe, CprE Jacob Rasmuson , CprE Arthur Fiester , CprE Alex Rannow , EE Tim Fox, EE Academic Advisor: Dr. Ahmed E. Kamal Client: PowerFilm Solar, Inc. Client Representative: Brad Jensen. Senior Design SD1107 Solar Module Observation Device.

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Senior Design SD1107 Solar Module Observation Device

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  1. Students: Collin Howe, CprE Jacob Rasmuson, CprE Arthur Fiester, CprE Alex Rannow, EE Tim Fox, EE Academic Advisor: Dr. Ahmed E. Kamal Client: PowerFilm Solar, Inc. Client Representative: Brad Jensen Senior Design SD1107Solar Module Observation Device SD1107 - Solar Module Observation Device

  2. Executive Summary Problem Statement PowerFilm wishes to have a remote measurement device that can communicate with a smartphone application over a Bluetooth interface. Benefits of this device include the following: • Access to information about charging/discharging rates to give the user an in-depth look into the status of the device • Logging capabilities which will allow users to track the solar module’s efficiency while user is out of communications range • Estimated charging times which will allow the user to track the charge progress of the device • Real-time data which will help determine optimal placement angles to place the solar module SD1107 - Solar Module Obeservation Device

  3. Functional Requirements • Bluetooth-connected voltmeter/ammeter device interfaced with solar panel and storage battery • Smartphone application to receive data and to display battery life and charge time • Device settings must be modifiable by the smartphone application when connected • Multiple power states (Active, Standby, Sleep) • Must provide logging capability SD1107 - Solar Module Obeservation Device

  4. Non-Functional Requirements • Operating temperature range of -40°C ~ 105°C • Must be able to measure voltages of 0-15.5VDC, and currents 0-0.5A • Powered by solar panel’s storage battery • Maximum production cost of $20/unit SD1107 - Solar Module Obeservation Device

  5. Wishes • Smartphone app with graphing capability to display data (zoom) • USB and/or GSM connectivity • User-defined sampling rates (1/2 second – 1 hour intervals) • Smartphone app able to control multiple solar devices • Tabbed user interface • A 1 in2 footprint PCB SD1107 - Solar Module Obeservation Device

  6. Constraints and Limitations Development • Time • PCB construction • Access to development community • Experience with programming with the microcontroller and Android application Device • Small size of PCB (less 3 in2) • Low power consumption (Must draw no more than 50 mA of current in full operation) • Maximum production cost ($20) SD1107 - Solar Module Obeservation Device

  7. Solution • TI MSP430F5438 microprocessor with PAN1315 Bluetooth radio connected to sampling circuitry • Integrated Bluetooth antenna inlaid in PCB • Mobile phone application running on a Bluetooth-enabled Android phone • Android application programmed in Java using Eclipse IDE SD1107 - Solar Module Obeservation Device

  8. SystemOverview PowerFilm wishes to have a remote measurement device to monitor the status of a solar device. This will allow users to observe real-time and logged data directly from a smartphone. SD1107 - Solar Module ObeservationDevice

  9. Technology/Tradeoffs MSP430+PAN1315 vs. CC2540 vs. Other All-In-One MCU/Radio • The MSP430 + PAN1315 option is somewhat more expensive than some other options • Relatively better support community • Complete system and demo/evaluation equipment • Uses universally-accepted Bluetooth2.1+EDR (the CC2540 used newer, backwards-incompatible Low Energy Bluetooth that has yet to be implemented in any end-user devices) Component Antenna vs. PCB Inlaid Antenna • Component antenna provided pre-engineered Bluetooth 2.4GHz antenna • Component antenna adds expense (no extra monetary expense for using PCB inlaid antenna from TI Designs) • Inlaid PCB antenna requires relatively large footprint of 1 in2 SD1107 - Solar Module Obeservation Device

  10. Project Schedule SD1107 - Solar Module Obeservation Device

  11. Work Breakdown SD1107 - Solar Module Obeservation Device

  12. Market and Literature Survey • There are quite a few devices on the market which measure voltage and current with a few being made specifically for solar panels. • Many of these require an external power source and can be controlled with a pc over wireless. • None of the devices are controllable over Bluetooth. Also the monitors were much bigger and required more power than our requirements. SD1107 - Solar Module Obeservation Device

  13. CostBreakdown SD1107 - Solar Module Obeservation Device

  14. Potential Risk • Lose a developer: Avoid issues by having substitutes and good documentation • Possibleissues with Bluetooth: Use a simpler Bluetooth mode • Faulty schematics from manufacturers: Troubleshoot and adapt SD1107 - Solar Module Obeservation Device

  15. Sensing Circuitry: Overview Current Sensing • 20 mΩ sense resistor in series with lines of interest • Voltage drop across resistor fed into 200 V/V differential amplifier • Output of amplifier fed into ADC of microcontroller • Use ratio of 0.25A/V to calculate current • 2.4 V Zener diode placed at ADC for protection Voltage Sensing • Accomplished by voltage divider • Input voltage scaled by a factor of 1/7.8 • 2.4 V Zener diode placed at ADC for protection SD1107 - Solar Module Obeservation Device

  16. Sensing Circuitry: Schematic SD1107 - Solar Module Obeservation Device

  17. Sensing Circuitry: Testing Initial Test: PSpiceSimulation • Test successful • Confirmed scalingratios • Continued to next step in testing SD1107 - Solar Module Obeservation Device

  18. Sensing Circuitry: Testing & Results Second Test: Scale Model • Built voltage divider and current sensing circuit on bread board • Used parts from EE 330 lab kit • Not exact values of resistors, but useful to confirm sound design sound • Output conformed to expectations • Nothing worked as expected initially on PCB • Voltage Sensing: • Resistors were swapped in voltage divider • Short in one of the protection Zener Diodes • Successfully fixed, working • Current Sensing: • Biasing voltages (Vcc and –Vcc) unconnected • Despite troubleshooting attempts, still not working Results SD1107 - Solar Module Obeservation Device

  19. Schematic: Microcontroller and Bluetooth Transceiver

  20. Microcontroller and Bluetooth Radio Microcontroller: TI MSP430F5438 • Powerful microcontroller with low power consumption • Able to run open-source BTStack with the Panasonic Bluetooth radio • 12-bit ADCs provide satisfactory accuracy for voltage/current measurements Bluetooth Radio: Panasonic PAN1315 • Designed to work with (recently deprecated) TI-MSP430F5438 Bluetooth Solution • Compatible with BTStack • Provides satisfactory range for application SD1107 - Solar Module ObeservationDevice

  21. Bluetooth Implementation Solution: BTStack on TI MSP430 • Development board very similar to solution we wished to implement • Interfaced with PAN1315 radio on plug-in board • Initially supposed to work with MindTree Bluetooth stack (now deprecated) • Proven to work with open source BTStack • ADCs available for prototyping SD1107 - Solar Module ObeservationDevice

  22. Microcontroller Solution BTStack on TI-MSP430 • Bluetooth device communicates with Android using Bluetooth’s Serial Port Profile (character-based) • Smooth pairing, handling of out-of-range/back-in-contact cases • Logging and real-time updates interrupt-driven; nearly infinitely definable • Circular log keeps only most recent/relevant data should device ever overflow onboard memory reserved for logs • Strictly defined operation; very reliable microcontroller application SD1107 - Solar Module ObeservationDevice

  23. Microcontroller/Bluetooth Testing Microcontroller Software/ADC Testing • Well-defined states and Dev Board LCD output made functional testing easy • Ensure ADC Linearity, Test/Pattern ADC measurements (0V to Vcc2.5v) • Test logging functionality • Bluetooth Communication • Well-defined packets between measurement device and Android phone • Range testing up to 50 meters • Integration Testing • Full functionality, range, & data rate testing complete with Android application • Difficulty with PCB has limited full integration testing with sensing circuitry

  24. PCB Overview Implementation • Used CadSoft’s Eagle PCB layout design software • Client supplied surface-mount device libraries • Gerber files sent to client for fabrication • Client-assisted mounting of microcontroller and radio onto PCB • Received assistance from Computer Support Group in mounting smaller components onto PCB • Manually mounted remaining parts • Problems Encountered • Microcontroller internal clock faulty • No power or biasing for op-amp • Bluetooth radio extremely difficult to mount manually • Texas Instruments provided faulty schematics • Bluetooth Stack provided for the MSP430f5438a was deprecated and support dropped SD1107 - Solar Module ObeservationDevice

  25. PCB Layout: MSP430+PAN1315 • Designed using CadSoft’s Eagle PCB design software • 3” x 3” area • Surface-mount devices • Could potentially be shrunk down to 1” x 1” in future projects SD1107 - Solar Module ObeservationDevice

  26. Application: Platforms/Tech Android APK vs. Apple IOS Both contain very powerful debuggers and interface builder along with a strong programming community. Android allows for more robust access to their Bluetooth libraries compared to IOS which require validation to use their Bluetooth API. Java vs. C/C++ Android provides excellent programming support and tutorial based on Java. C and C++ lack the support and necessary libraries for the scope of this project . Eclipse and ADT The Android APK is designed to work with Eclipse and make available its own development tools. SD1107 - Solar Module ObeservationDevice

  27. Application: Implementations Device Screen Contain controls for connect/disconnect along with real-time data toggle and sample rate controls. Logging Screen Contains controls for the logging toggle and the logging sample rate. In addition, it houses the controls to remove the device and its logged data. SD1107 - Solar Module ObeservationDevice

  28. Application: Implementations Data Screen Shows table information via table or graph. The graph will query all logs while the graph will show only voltage, current, or power. The graph is scalable and scrollable. Behind the curtains SQLite Database: Contains two tables, Device and Data. The Device table retains SMOD information such as name, address, and sampling rates. The Data table includes log data from the SMOD. BluetoothServiceThreads: Creates and updates threads for connecting, disconnecting and receiving, and transmitting packets from the SMOD GraphView API: We used open source libraries for drawing and altering the data graphs SD1107 - Solar Module ObeservationDevice

  29. Application: Test Plan Usability Testing Four iterations of polling possible users and the client for input on the GUI structure and general functionality of the application Performance/Responsive Testing Tested the responsiveness of the GUI with a round trip Bluetooth transmission and packet receiving with respect to the computation time of the microcontroller. Also tested computation time of the GUI when displaying and drawing log data. Integration Testing Tested for correct, precise, and consistent behavior between the Android application and the microcontroller on the experimenter board. SD1107 - Solar Module ObeservationDevice

  30. Application: Test Results Usability Testing Iteration 1: Added table data view • Iteration 2: Condensed adding new device behavior from 2 to 1 screen • Iteration 3: Removed graph view glitches • Iteration 4: Removed unnecessary buttons and test elements Performance/Responsive Testing Required us to condense packet traffic for responsiveness. Additionally we changed the GUI and database structure to decrease wait time for graph drawing Integration Testing General debugging to remove unwanted and abnormal behavior SD1107 - Solar Module ObeservationDevice

  31. Conclusion • Working Android Application • Working Bluetooth Connection/ Bluetooth stack • Working microcontroller software • Sensing circuitry works in PSpicemodel • Measures voltages but does not measure current SD1107 - Solar Module Obeservation Device

  32. Future Work • Smaller, marketable PCB • Android App ported to iOS • Update Android App to improve usability, performance, and visual appeal • Possibly change to a less expensive microcontroller than the MSP430 series SD1107 - Solar Module Obeservation Device

  33. Lessons Learned & Client Feedback • Double, triple check designs and schematics • Designing and soldering a PCB • Mr. Jensen, our client, was impressed with the voltage sensing and Bluetooth implementation results that were demonstrated • This project can be expanded upon in future senior design projects SD1107 - Solar Module Obeservation Device

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