Bluetooth Monitor for PowerFilm Solar Panels SDDEC1107 Alex Rannow, Tim Fox, Arthur Fiester, Jacob Rasmuson, Collin Howe

Project Goal PowerFilm Solar Inc. wishes to have a device that can monitor voltages and currents of their foldable solar panels. The project is to design a remote measurement device that can communicate with a smartphone. A Bluetooth device, that can communicate with an Android phone over Bluetooth. A counterpart Android application that is able to control and monitor the device and estimate battery life and charging time.

Concept Sketch

Functional Decomposition The project can be decomposed into three ‘Blocks’ Sensing: The circuitry that allows the microprocessor to sense voltage and current at measurement points. Processing: The microcontroller itself. This is where the data is interpreted, logged, and broadcast. Displaying: The Android phone app. This configures the processing, receives the data broadcast, and displays it to the user.  Sense Current: -From Solar panel -Into Device Being Charged  Sense voltage: battery being charged Sensing  Receive Bluetooth data  Control processing via Bluetooth  Display data in a user friendly format Displaying  Process the data from the sensors  Log data from the sensors  Broadcast requested data via Bluetooth Processing

System Architecture

Technology Choices/Platforms CSR : BC4 PC-ROM Bluetooth 2.1 +EDR onboard microcontroller. Satisfies all requirements except it contains an onboard 8-bit ADC in which requirements specify we need a 12-bit ADC. The ADS7866 will be attached to provide a 12-Bit ADC. TI CC2540 Bluetooth Low Energy (BLE) onboard microcontroller. Satisfies all requirements except the Bluetooth compatibility. BLE's new standard is not backwards compatible and will not connect with modern Android devices. An external Bluetooth radio will be necessary. TI MSD430F2013 a 14-pin microcontroller that has no Bluetooth capabilities but is within our low energy standard and well below the budget. A simple external Bluetooth radio will be needed to fulfill all requirements.

System Analysis/Design Tradeoffs Power Used Vs. Transmit Power The power requirement restricts the possible power we can use in Bluetooth radio communication. Antenna size Vs. Gain A larger antenna will provide more gain. We area restricted to 1” by 1”, so we must use an antenna that fits within that requirement.

Module Design Microcontroller & Radio The microcontroller must be able to use the radio to communicate with the Android device. Current/Voltage Scaling Steps down high voltage to ADC level, amplifies voltage drop across very small resistance to measure current.

Module Design Power Supply Supply constant power at a stable voltage to the microcontroller and radio Android Application Poll the device at user-specified intervals and report back to the user. Display data in friendly format and allow user to change polling settings.

Interface Design Bluetooth Radio Communication Well defined by standards Current/Voltage Sensors Analog scaling circuits for ADC conversion Android Application Human interface

Test Plan PerformanceTestPreliminary results Accuracy of measuring voltages and currents.IMM5% error from actual input Battery Capacity/ charging time predictionIMM Range of voltages/currentsIMM volts and amps Input sampling rates(upper bound) via Android parameters IMM, System 5 samples/sec with < 1 second propagation delay ADC Input resolutionIMM, System2 decimal places Current consumption of deviceIMM, MC Active mode: < 300 µamp Standby/Hibernate mode: < 1 μamp Data rate between application and MCMC, App Perform properly and consistently under durability temperature range test SystemRange : -40 to 105 Power mode state change via AndroidMC, Android<1 second propagation delay Compatible with different android devicesApp Off switch safely powers down deviceSystem, MC Power surge protectionIMM, MC, SystemOperates within normal parameters Independent data updating to Android functionality is consistently working MC, App, System Works when connection denoted by the application Consistent Connect/Disconnect via AndroidMC, App Bluetooth rangeMCAt least 100 feet

Schematic

Schematic, Microcontroller

Cost Estimation ItemCost CSR : BC4 PC-ROM2.30 ADS HHM Measurement Components2.00 Module Cost5.88

Questions?