Microcontroller Compensated Micromachined Oscillator Circuit

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MicrocontrollerCompensatedMicromachinedOscillator CircuitGroup 13:Megan Driggers, EEHeather Hofstee, EEMichaela Pain, CpESponsored by:Dr. Reza Abdolvand

Oscillators Overview Oscillators are heartbeat of electronics Necessary for stable signals and proper clocking Clock signals ensure data is not lost in delays Crystal oscillators are most common

Micromachined Oscillator Overview Micromachined oscillators/resonators: fabrication and smaller Issues arise with temperature stabilityFigure 1: 3D rendering of micromachined oscillator

Motivation Researchers at UCF work with thin-film piezoelectric-onsilicon (TPoS) microsystems resonators TPoS resonators: active compensation Project sponsor: Dr. AbdolvandFigure 2: Fabricated oscillators on silicon

Goals and Objectives Goal: to build a PCB that stabilizes resistance of resistor Resistance Temperature To be used in testing TPoS oscillators Unique temperature and resonance frequency characteristics

Requirements Hardware Deliverables: Controls resistance within mΩ Protection for resonator/functional checks Communication Relay temperature and resistance to user Software Deliverables: Controls resistance within mΩ Correct speed of program for stability

SpecificationsFeatureValueProject Budget 1000Completion Time31 weeks totalAccuracyResistance within1mΩSystem: ambient roomtemperature(approximately 23 C)OperatingTemperaturesResistance DeviationStart up timeLow PowerResonator: greaterthan 85 C(approximately 90 C)1mΩ 3second 20W

Overall System DesignOther Tasks:Power SupplyControl B Designand AssemblyDisplay andUser InputFeedbackResponsibility of:HeatherMeganMichaela

COMPONENTSELECTION

LCD Selection The TinSharp 16x2 screen was selected as the Liquid CrystalDisplay (LCD) because: Its size allowed for flexibility in the presentation of results and user prompts Compatibility and costProductLCMH01604DSFEA nufacturer DriverVoltageLumex5VCharacterArrangement16x4Number ofpins16Display TypePriceSTN, Transflective 27.92ElectronicAssemblyTinSharp5V8x214 16.975V16x216MicrotipsTechnology4.5V20x216Neutral, Blu-Contrast,STN, ReflectiveSTN, Transmissive,Negative, BlueSTN, Transmissive,NegativeGravitech4.7V20x416STN yellow green 14.35 9.95 15.74

0 TCR Resistor The 10Ω resistor was chosen as the 0TCR resistor because: Considering the 10V power source, aresistance greater than 10Ω would pulltoo much voltage Low price point and small and standardpackaging The options shown are manufactured byVishay Foil Resistors (a division of VishayPrecision Group) and have a TCR value of0.2 ppm/ CProductResistance Case Code(inches)Y16285R00000D0W 5Ω2512Price 16.75Y1625100R000Q9R100Ω1206 12.75Y402310R0000C9R10Ω1206 17.64Y1630250R000T9R250Ω1206 11.56Nonstandard0805 13.60Y11191R00000D9W 1ΩY162910R0000C9R10Ω 9.48

Microcontroller Series SelectionFeatureOperating VoltageManufacturerComm. InterfacesPin CountBit CountLow PowerPowerConsumption inActive ModeApprox. PriceMSP4301.8 V – 3.6 VTexas InstrumentsUART, SPI, I2C20 16-bitYes330 µA/MHzMSP4321.62 V to 3.7 VTexas InstrumentsUART, SPI4032-bitYes95 µA/MHzPIC24F2.0 V – 3.6 VMicrochip Tech.UART, SPI, I2C2616-bitYes300 µA/MHzGecko1.98 V – 3.8 VSilicon LabsUART, SPI3232-bitYes63-225 µA/MHz 14.99 12.99 4.99 29.99The MSP430 series microcontroller was chosen because: Familiarity with the family of microcontrollers Low cost High resolution A/D convertor options within series D/A convertor options within series

Microcontroller Product SelectionFeatureMSP430FG47xMSP430G2xMSP430F552xPin nalogResolutionAdditional features16-bit10-bit12-bit12-bitN/AN/AFive low-powerOn-board buttons andmodes, digitallyLEDs, modules forcontrolled oscillator added functionalityOn-board emulationfor programming anddebuggingApprox. Price 9.99 12.99 9.99The MSP430FG47x microcontroller was chosen because: Provides enough pins to connect LCD, user interface, and voltage readings Allows for an external crystal oscillator to increase clock speed Low cost Contains a D/A convertor Highest A/D resolution

Microcontroller Voltage ReadingsInside MicrocontrollerResonator16-bitADCFigure 3: Microcontroller ADC visual representation Goal: Maximize resolution of voltage readingsthrough 16-bit A/D Convertor How: Manipulate input voltages to span overthe entire microcontroller ADC input voltagerange (0V to 1.5V)Figure 4: INA828 pin 28 Gain Resistor𝟓𝟎𝐤𝛀𝐆𝐚𝐢𝐧 𝟏 𝐑𝐆Figure 5: Voltage Divider CircuitVoltage Divider Circuit Gain𝟏𝑹𝟏𝟕 𝑹𝟏 𝑹𝟐Gain

POWER SUPPLY

Power SupplyThe main power supply was chosen to be the Agilent E3631A triple DC voltageoutput because: Already present in Dr. Abdolvand’s Lab Able to provide both 10V and -10V rails High stability/low voltage variationComponentSupply Voltage(s) 10VVoltageRegulatorMain Power eReference3V3.3V-1.4V-10VInstrumentationAmplifiers 10V-10VOperationalAmplifier 10V-10VLCD Display5VLCD Contrast Pin-1.4VMicrocontroller/LCD Logic3.3VADC and DACReference VoltageCircuit InputVoltage3V8.2V

Voltage RegulatorsThe most important aspect of voltage regulation for our project: ***Low noise*** High efficiency Acceptable powerComparison of Voltage Regulator wer CapacityLowHighHighMediumHighLowHighHighLowLinear voltage regulators would be the best option

EAGLE SCHEMATICAND BOARD DESIGN

EAGLE Schematic DesignMain Power Supply (10V) to LCD Logicand Microcontroller Power Supply (3.3V)Figure 6: 10V to 3.3V conversion circuitMain Power Supply (10V)Backlight Power Supply (5V)toLCDFigure 8: 10V to 5V conversion circuitMain Power Supply (10V) to CircuitInput Voltage (8.2V)Figure 7: 10V to 8.2V conversion circuitVoltage Reference (3V) forMicrocontroller ADC and DACFigure 9: 3V voltage reference circuit

EAGLE Schematic DesignMicrocontroller ConnectionsLCD ConnectionsContrast pinvoltage supplyFigure 10: LCD schematicJTAG InterfaceFigure 11: Microcontroller connections schematicUser Interface/ButtonsExternal CrystalVoltage InputFigure 12: Voltage input, crystal, and programminginterface schematicFigure 13: User interface schematic

EAGLE Analog Schematic DesignResonator voltage readingVoltage DividerRelay0TCR resistor voltage readingVoltage limiterVoltage to currentconverterFigure 14: Analog schematicVoltage limiter

EAGLE Analog Schematic DesignFigure 14: Analog schematic

EAGLE PCB DesignLCDJTAGinterface MicrocontrollerIn. amp., relay,& resonatorVoltage ref.CrystalSwitchesIn. amp for 10ΩVCCVolt. Reg.VoltageInputFigure 15: PCB design

Populated PCBLCDJTAGinterface MicrocontrollerIn. amp., relay& resonatorVoltage ref.CrystalSwitchesIn. amp for 10ΩVCCVolt. Reg.VoltageInputFigure 16: Populated PCB

Populated PCBFigure 16: Populated PCB

SOFTWARE

Software Functionality The purpose of the software is illustrated in the tasks below: Calculating the resistance of the resonator Communicating information between the user and device Controlling the current passed into the resonator Other requirements include: Operating in three modes: Standby Characterization OperationalScalable and efficient code

Programming Language C was selected as the programming language for thisproject because: Often the language of choice for this type of application Programs for embedded applications tend to not be object-orientedBuild-in and user-defined types, data structures and flexiblecontrol flow (1) Previous background in C programming

Programming Environment Code Composer Studio was selected as the software developmentenvironment because: Designed for TI’s microcontrollers and embedded processors Contains a multitude of tools for development and debugging embedded applications Compatible with our microcontroller Previous software experienceToolDescriptionCCS CloudCloud-based IDEEnergiaIntuitive, easy-to-use and Windows, Mac and In-line C,open source IDELinuxassemblyFull-featured, eclipseWindows and Linux C/C based IDECode ComposerStudioOperating SystemProgrammingLanguagesN/A – Web browser C/C Additional SupportCloud-hosted workspace and TIResource ExplorerFramework of APIs and codeexamplesEnergy Trace and ULP Advisortools

Resistance Control Algorithm A proportional integralderivative (PI) controller wasused to implement controlsystem to stabilize the resistance Figure 17: PID Control SystemSource: roller/Takes action based on past,present and prediction of futurecontrol errors Delivers control output at desiredlevelsFigure 18: Graphical Representation ofControllerSource: Analysis and Design of Feedback Systems by Astrom and Murray

Resistance Control Algorithm Our PI controller algorithm works as follows: Continuously calculates the error Calculates a correction based on proportional and integral terms The P-term is proportional to the current error The I-term is proportional to the integral of the errorApplies the correction to modify the current output Which in turn affects the voltage and resistance Loop tuning was used to produce the optimal control function

Initial Control System Testing When the resonator’s transfer function isapproximated to a first order system of form:𝑏𝑠 𝑎 𝑏 𝑒 𝑎𝑡 𝑢(𝑡)2𝜁𝜔0 𝑎,𝑏𝜔0 2𝑏 𝐾𝑝 The ‘b’ for each system is dependent on its𝐾𝑖 resistance and is different for each system. Figure 19: Initial control system testing(constant 𝐾𝑝 and 𝐾𝑖 )Error E(t) Resistance-Desired Resistance (For negative TCR)Controller 𝐾𝑝 𝐾𝑖𝑠The data shows that for constant 𝐾𝑝 and 𝐾𝑖values, the overshoot changes linearly withthe system’s resistance. Therefore, 𝐾𝑝 and 𝐾𝑖 are both inverselyproportional to the resistance.

Resistance Control System ResultsFigure 20: 15Ω Resistor overshoot analysisFigure 22: 22Ω Resistor overshoot analysisFigure 21: 15Ω Resistor time analysisFigure 23: 22Ω Resistor time analysis

Program ionOperational

Program FlowStandbyExiting Update LCDModeCharacterizationPromptinput: select modeExiting Update LCDModeUp: select mode: re-input currentOperationalExiting date LCDCalculatecurrentOutputvoltageModeUp: select mode: re-inputresistance

urevaluesCalculateresistanceUpdate date LCDMeasurevaluesCalculateresistanceUpdate ationalPromptinputOutputvoltage

LCD Testing The evaluation of the software is critical for verifying thecorrect performance of the application The software component of this system was required to receiveaccurate voltage inputs and perform calculations andconversions appropriately The LCD was used to debug and present measurements to thetester during program development

ADMINISTRATIVE

Work DistributionTeam MemberTasksMeganHeatherTeam CoordinationPResonator TestingPOverall SchematicSPPCB Schematic DesignPSPCB Board DesignSPPCB Assembly/ SolderingPPPower SuppliesPControl System DesignPDisplay and User InputSSSPMicrocontroller ProgrammingComponent SelectionKey: P Primary, S SecondaryMichaelaPPPP

BudgetVendorExpenseCostAdvanced CircuitsPCB (Quantity: 2) 89.771st BoardIterationDigikeyParts 43.77MouserParts 89.642nd BoardIterationAdvanced CircuitsPCB (Quantity: 1) 122.61MouserParts 86.083rd BoardIterationPCBWayPCB (Quantity: 5) 74.00MouserParts 85.39eBayMSP430 Programming FET 27.95Total budget remaining: 380.79Total spent: 619.21Other

Current ProgressResearchHardware DesignSoftware DesignPrototypingTestingOverall758085Percent Complete (%)9095100

Challenges and Takeaways Difficulties: PCB design, little experience Software and hardware integration Lessons: Teamwork, research carefully, be flexible

Final Thoughts Acknowledgements Optimize current range Control loop for positive TCR device Write up user instructions

Questions?

EAGLE Schematic Design Main Power Supply (10V) to LCD Logic and Microcontroller Power Supply (3.3V) . In. amp., relay, & resonator Figure 15: PCB design. Populated PCB . PCB Schematic Design P S PCB Board Design S P PCB Assembly/ Soldering P P Power Supplies P

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