Senior Design SD1107 Solar Module Observation Device Team Leader: Collin Howe, CprE Webmaster: Jacob Rasmuson, CprE Communications: Arthur Fiester, CprE.

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Senior Design SD1107 Solar Module Observation Device

Team Leader: Collin Howe, CprE Webmaster: Jacob Rasmuson, CprE Communications: Arthur Fiester, CprE Team Member: Alex Rannow, EETeam Member: Timothy Fox, EE

Academic Advisor: Dr. Ahmed E. KamalClient: PowerFilm Solar, Inc.Client Representative: Brad Jensen

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Agenda

• Executive Summary• Project Overview• Modules• Sensing Circuitry• Microcontroller• Android Application

• Development• Schedule and Cost

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Problem 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. • 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.

Executive Summary

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• 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

• A 1 in2 footprint PCB• 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• Multiple power states (Active, Standby, Sleep)• Maximum production cost of $20/unit• Must log data over specified time if so configured by user

Requirements

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• 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

Wishes

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Development• Time• Access to development community• Experience with programming with the microcontroller and Android

application

Device• Small size of PCB (less 1 in2)• Low power consumption (Must draw no more than 50mA of current

in full operation)• Maximum production cost ($20)

Constraints and Limitations

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• TI MSP430F247 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

Solution

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System Overview

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Losing a team member Unable to utilize Bluetooth PCB integration Component damage during fabrication Design is incorrect and requires rework

Risk Management

MSP430+PAN1315 vs. CC2540 vs. Other All-In-One MCU/Radio:• The MSP430 + PAN1315 option is somewhat more expensive than some

other options• Much 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 on our PCB

Technology/Tradeoffs

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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

Voltage Sensing • Accomplished by voltage divider• Fraction of Vcc inputted into ADC of microcontroller

2.1 V Zener diode placed at ADC for protection

Sensing Circuitry: Overview

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Schematic: Sampling Circuitry

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Microcontroller: OverviewADC Interface to the Current/Voltage sensing circuits• 12 bits of resolution• Measure VIA timer interrupt at certain user-defined intervals (1/2

second to 1 hour)• Software scaling to actual voltages/currents

Bluetooth Radio Control• Communicate with TI/PAN1315 Bluetooth Radio over UART• Initiate as device using SPP (Serial Port Profile)• Communicate through MindTree/TI Bluetooth Stack VIA RTOS (Free

Real Time Operating System, open source)

Power States• Able to lower power state of MSP430 into “standby” and “sleep”

modes through software/radio control

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Microcontroller: Device Concept

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Microcontroller: Program Structure

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Schematic: Microcontroller and Bluetooth Transceiver

LEDs implemented in prototype only

To Current &Voltage

sensing circuits

To power supply(2V to 3.6V DC)

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• Makes use of Bluetooth on the Android hardware to interface with our device.

• Communication over GSM and USB are desirable possibilities as well, but might be unfeasible.

• Must be able to alter the configuration of the monitoring device (such as sampling rates and logging options).

• Incorporate data from the device into a friendly user interface.

Android Application: Overview

Android Application: GUI

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Home Screen• Display current status of tethered devices and

provide quick access to them.• Allow access to application wide variables

Device Screen• Controls power state and pinging function• Displays up-to-date voltages and currents along

with a graph of previous data• Allows user to set device settings

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Android Program Structure

Testing

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Module Testing: Determine if each module is working independently.(Test voltage/current for correct output based on controlled input. Test Android application against previously-implemented SPP terminal device)

Integration Testing:Once it is determined that each module is working within respective parameters we will integrate all three modules in a lab environment

System testing:Finally the system test will involve system integration between our working device and a testbed solar panel in “real world” conditions.

Testing

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Test Module Preliminary ResultsAccuracy of measuring voltages and currents. IMM 5% error from actual input

Battery Capacity/ charging time prediction IMM

Range of voltages/currents IMM 1-15.4 volts and 0.01-0.5 amps

Input sampling rates(upper bound) via Android parameters IMM, System 5 samples/sec with < 1 second propagation delay

ADC Input resolution IMM, System 2 decimal places

Current consumption of device IMM, MC Active mode: < 300 MicroampStandby mode: < 1 MicroampHibernate mode: < 1 Microamp

Data rate between application and MC MC, App

Perform properly and consistently under durability temperature range test

System Range : -40 to 105

Power mode state change via Android MC, Android <1 second propagation delay

Compatible with multiple and different android devices App

Off switch safely powers down device System, MC

Power surge protection IMM, MC, System Operates within normal parameters

Independent data updating to Android functionality is consistently working

MC, App, System Works when connection denoted by the application

Consistent Connection/ Disconnection via Android MC, App

Bluetooth range MC

Completed Tasks• Project plan & design document• Technology Selection• Detailed Design including all schematics• Acquired components and development tools• Tested and verified the sampling circuitry• Android Application development

Remaining Schedule• Module development and testing• Establish Bluetooth connectivity• Integrate sampling circuitry with microprocessor• End product testing and debugging

Schedule

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Cost EstimationEnd Product

Component Part Quantity Price

Sense Resistor RL16T.0206CT-ND 2 0.88

Op Amp NJM2710 1 1.62

Zener Diode FLZ3V9B 1 0.08

Protect Zener Diode BZX84C2V4S 2 0.44

Bluetooth Radio PAN1315 1 8.71

Microcontroller MSP430F247 1 3.41

Total $15.86

Development

Component Part Price

Experimenter board RL16T.0206CT-ND 150

Evaluation Module Pan 1315 99

Debugging Interface FLZ3V9B 99

Total $348

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Questions?

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