ECE 480 – Team 6OutlineIntroductionCapacitive Sensor BasicsDesign RequirementsSystem Block DiagramDesign FlowchartSensor TracesCapacitance-to-Digital ConverterMicrocontrollerBudgetCapacitive vs. OpticalSoftwareDemonstrationConclusionsQ & AThank You1ECE 480 – Team 6In Order of Presentation:Ishaan SandhuDanny KangArslan QaiserEric OtteAnuar TazabekovCapacitive Rain Sensor for Automatic Wiper Control2Outline• Introduction• Design Requirements• Proposed Design Solution• Testing Results• Budget• Demonstration• Conclusions3Introduction•Automotive Safety and Convenience•Automatic Headlights•Hands-Free Calling•Automatic Braking•Automatic Windshield Wipers–Currently Optical (Expensive, Inaccurate)–DT6 Proposes Using a Capacitive Based Sensor4Capacitive Sensor Basics5Design RequirementsFunctionality• Detect rain through 6 mm of glass• Output control signals to wipersAccuracy• Differentiate multiple levels of rain• Ignore false stimuli on windshield, i.e. hands and dirtCompatibility• Fit in existing housing area (1250 mm2)• Mount via adhesive to windshield Cost• Production cost < $16 per unit6System Block Diagram7Design FlowchartControl Unit8Sensor TracesCOMSOL •3D Modeling Software •Visual User Interface•Calculates the base capacitance •Can model dielectrics–Top layer–Bottom Layer•Simulates electric field lines–Sensitivity9Capacitance-to-Digital ConverterAnalog Devices AD7745•Industry-leading accuracy down to 4 fF change in capacitance•Interfaces with sensor traces to monitor capacitance (+/- 4 pF)•Converts changing capacitance to 24-bit digital output signal•Output routed to PIC using the I2C communication systemMake text larger10MicrocontrollerMicrochip PIC16F1826•8-bit microcontroller, programmable in C code•Initializes and configures AD7745 for operation•Streams data from AD7745 and compares to known data ranges•Data falling in range will activate appropriate wiper control signalsMake text larger11BudgetCOMPONENT COSTPIC16F1826 Microcontroller $0.90AD7745 CDC $4.50ADP3301-5 Voltage Regulator $1.40Surface-mount Passive Components $0.10Two-layer PCB Production and Assembly $4.00 (est)Plastic Enclosure $0.50 (est)Total $11.40 (est)12 Capacitive vs. OpticalDesign Team 6 Supplier (TRW) ChangeTechnologyCapacitive OpticalCost per Unit$11.40 $16.41 31% ↓Physical Size1,750 mm23,850 mm246% ↓Detection Area960 mm2560 mm272% ↑Clear line of siteNo need Required13Software14Demonstration15Conclusions•Successful completion of the project•Exceeds all design requirements•Higher accuracy•Larger sensing area•Smaller enclosure•Significant savings16 Q & A17Thank
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