Capacitive Rain Sensor for Automatic Wiper Control ECE

Capacitive Rain Sensor for Automatic Wiper Control ECE 480 – Team 6 In Order of Presentation: Ishaan Sandhu Danny Kang Arslan Qaiser Eric Otte Anuar Tazabekov 1

Outline • Introduction • Design Requirements • Proposed Design Solution • Testing Results • Budget • Demonstration • Conclusions 2

Introduction • • • Automotive Safety and Convenience Automatic Headlights Hands-Free Calling Automatic Braking Automatic Windshield Wipers – Currently Optical (Expensive, Inaccurate) – DT 6 Proposes Using a Capacitive Based Sensor 3

Capacitive Sensor Basics 4

Design Requirements Functionality Compatibility • Detect rain through 6 mm of glass • Fit in existing housing area (1250 mm 2) • Output control signals to wipers • Mount via adhesive to windshield Accuracy Cost • Differentiate multiple levels of rain • Production cost < $16 per unit • Ignore false stimuli on windshield, i. e. hands and dirt 5

System Block Diagram 6

Design Flowchart Control Unit 7

Sensor Traces COMSOL • 3 D Modeling Software • Visual User Interface • Calculates the base capacitance • Can model dielectrics – Top layer – Bottom Layer • Simulates electric field lines – Sensitivity 8

Capacitance-to-Digital Converter Make text larger Analog Devices AD 7745 • Industry-leading accuracy down to 4 f. F change in capacitance • Interfaces with sensor traces to monitor capacitance (+/- 4 p. F) • Converts changing capacitance to 24 -bit digital output signal • Output routed to PIC using the I 2 C communication system 9

Microcontroller Make text larger Microchip PIC 16 F 1826 • 8 -bit microcontroller, programmable in C code • Initializes and configures AD 7745 for operation • Streams data from AD 7745 and compares to known data ranges • Data falling in range will activate appropriate wiper control signals 10

Budget COMPONENT COST PIC 16 F 1826 Microcontroller $0. 90 AD 7745 CDC $4. 50 ADP 3301 -5 Voltage Regulator $1. 40 Surface-mount Passive Components $0. 10 Two-layer PCB Production and Assembly $4. 00 (est) Plastic Enclosure $0. 50 (est) Total $11. 40 (est) 11

Capacitive vs. Optical Design Team 6 Supplier (TRW) Technology Change Capacitive Optical Cost per Unit $11. 40 $16. 41 31% ↓ Physical Size 1, 750 mm 2 3, 850 mm 2 46% ↓ Detection Area 960 mm 2 560 mm 2 72% ↑ Clear line of site No need Required 12

Software 13

Demonstration 14

Conclusions • • • Successful completion of the project Exceeds all design requirements Higher accuracy Larger sensing area Smaller enclosure Significant savings 15

Q&A 16

Thank You 17