senior design sd1107 solar module observation device

Senior Design SD1107Solar Module Observation DeviceStudents:

Collin Howe, CprE Jacob Rasmuson, CprE Arthur Fiester, CprEAlex Rannow, EETim Fox, EE

Academic Advisor: Dr. Ahmed E. Kamal

Client: PowerFilm Solar, Inc.

Client Representative: Brad Jensen

SD11

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Sola

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Obs

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Devi

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Executive SummaryProblem StatementPowerFilm 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 moduleSD1107 - Solar Module Obeservation Device12/4/2011

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 capabilitySD1107 - Solar Module Obeservation Device12/4/2011

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 Device12/4/2011

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 PCBSD1107 - Solar Module Obeservation Device12/4/2011

Constraints and LimitationsDevelopment 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)


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

Solution

12/4/2011

System OverviewPowerFilm 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.


Technology/TradeoffsMSP430+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

in2SD1107 - Solar Module Obeservation Device12/4/2011

Project Schedule


Work Breakdown


Collin Arthur Alex Tim JacobResearch Microcontrollers X X XResearch Radios/ Interfaces X XMicrocontroller Bluetooth Interfacing XAndroid Development X XAndroid Bluetooth Interfacing X XSensing Circuitry/Validation XPower/protection XMicrocontroller Development XPCB Design X XPCB Validation X X XDebugging X X X X X

12/4/2011

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.

12/4/2011 SD1107 - Solar Module Obeservation Device

Cost Breakdown


Potential Risk

Lose a developer: Avoid issues by having substitutes and good documentation

Possible issues with Bluetooth: Use a simpler Bluetooth mode

Faulty schematics from manufacturers: Troubleshoot and adapt


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


Sensing Circuitry: Schematic


Sensing Circuitry: Testing

Test successful

Confirmed scalingratios

Continued to next step in testing


Initial Test: PSpice Simulation

12/4/2011

Sensing Circuitry: Testing & Results

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


Second Test: Scale Model

Results

12/4/2011

Schematic: Microcontroller and Bluetooth Transceiver

12/4/2011

Microcontroller and Bluetooth RadioMicrocontroller: 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 applicationSD1107 - Solar Module Obeservation Device12/4/2011

Bluetooth Implementation

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

Solution: BTStack on TI MSP430


Microcontroller SolutionBTStack 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


Microcontroller/Bluetooth TestingMicrocontroller Software/ADC Testing

Well-defined states and Dev Board LCD output made functional testing easy

Ensure ADC Linearity, Test/Pattern ADC measurements (0V to Vcc 2.5v)

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

PCB OverviewImplementation 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


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


Application: Platforms/TechAndroid APK vs. Apple IOSBoth 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.


Application: Implementations

Device ScreenContain controls for connect/disconnect along with real-time data toggle and sample rate controls.

Logging ScreenContains 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 Obeservation Device12/4/2011

Application: ImplementationsData ScreenShows 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 curtainsSQLite 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. BluetoothService Threads: 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


Application: Test PlanUsability TestingFour iterations of polling possible users and the client for input on the GUI structure and general functionality of the application

Performance/Responsive TestingTested 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 TestingTested for correct, precise, and consistent behavior between the Android application and the microcontroller on the experimenter board.


Application: Test ResultsUsability TestingIteration 1: Added table data viewIteration 2: Condensed adding new device behavior from 2 to 1 screenIteration 3: Removed graph view glitchesIteration 4: Removed unnecessary buttons and test elements

Performance/Responsive TestingRequired us to condense packet traffic for responsiveness.Additionally we changed the GUI and database structure to decrease wait time for graph drawingIntegration TestingGeneral debugging to remove unwanted and abnormal behavior


Conclusion

Working Android Application

Working Bluetooth Connection/ Bluetooth stack

Working microcontroller software

Sensing circuitry works in PSpice model

Measures voltages but does not measure current


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


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


senior design sd1107 solar module observation device

Documents

powerfilm solar

solar modules efficiency

remote measurement device

charge time device settings

bluetooth interface

pcb mobile phone application

pan1315 bluetooth radio

logged data