Michigan State UniversityECE 480: Senior DesignFebruary 5th, 2010Capacitive Rain SensorFor Automatic Wiper ControlDesign Team Six:Eric Otte Danny KangArslan QaiserIshaan SandhuAnuar TazabekovFacilitator: Dr. John R. DellerPre-ProposalSponsor: Hyundai Kia America Technical Center (HATCI)Executive SummaryTechnological advances continue to enhance the safety and convenience of modern automobiles. Unfortunately, the increasing complexity of vehicles and the prevalence of mobile devices such as cell phones pose additional distractions for drivers. One feature designed to ease the burden on vehicle operators is the automatic rain-sensing wiper system, which detects rain on the windshield and automatically turns on the automobile’s wipers. This work is concerned with developing a new rain sensor based on capacitive-sensing technology to replace current optical sensor units, which can be prone to error. Capacitive-sensing relies on interactions with an electric fieldto determine the presence and location of an object. This capacitive rain sensor will utilize this property to detect the presence of moisture on the windshield and send signals to control the wipers accordingly. The prototypeunit will be designed and built by ECE 480 Design Team 6 and displayed at Michigan State University’s Design Day in April, 2010.Table of ContentsIntroduction ……………………………………………………………… 3Background ……………………………………………………………… 4Design Specifications ……………………………………………………..4Description of Conceptual Designs ……………………………………….5Hardware Specs …………………………………………………………...6Figure 1: Block Diagram of System ………………………………. 7Project Management ………………………………………………………9Table 1: Non-technical Roles ……………………………………...10Table 2: Technical Roles …………………………………………..11IntroductionIn the past two decades, the automobile industry has aggressively researchedways to exploit modern computing and electronic advances in the development of safety, reliability, and enhanced driver-interface technologies for vehicles. With each new model year, the array of technical features in automobiles continues to grow to unprecedented size. Previously remarkable and rare devices such as auto-dimming mirrors and rear-view cameras have become standard features in the modern era. Today consumers expect their automobile to be able to connect to their MP3 player, provide GPS-assisted visual directions, and allow hands-free phone calls via Bluetooth technology. While these features have improved the driving experience for many, they also highlight the increasingly common interaction between driver and electronic gadgetry during vehicle operation. These interactions can often become a dangerous distraction to the driver, who must take their eyes off the road to attend to the device. One feature designed to reduce driver distraction and add convenience is the automatic rain-sensing wiper system. These systems detect droplets of rain on the windshield and automatically turn on the wiper system, allowing the driver to focus on driving. Current rain-sensing systems use an optical sensor to determine the presence of moisture on the windshield, and relay data to a body control module to control the wipers accordingly. However, these optical systems are prone to errors, are physically bulky, and more expensive than necessary to make them a feature in most cars.ECE 480 Design Team 6, together with the Hyundai Kia American TechnicalCenter (HATCI), proposes the development of a capacitive-sense based automatic rain sensing wiper system to replace current optical units. The capacitive based sensor will provide greater accuracy, reduced size, and lower cost than the optical design. The capacitive sensor will mount to the interior of the windshield near the rear-view mirror in the same location as the optical unit, but with reduced physical size. The sensor circuitry will share similar communication and power interfaces with the optical unit to aid in rapid implementation. Control signals from the capacitive-sensor will be routed to a microcontroller in the prototype design, and will route to the body control module (BCM) in production designs to control the wiper motors.BackgroundCurrent automatic rain-sensing wiper systems use optical sensors exclusively as the tool to detect precipitation. In this design, infrared beams are transmitted, reflected, and measured to determine the presence of water. Early systems were inaccurate and produced many false readings, leading to the operator often turning the feature off. Modern optical sensors have improved accuracy but still suffer from being overly expensive and somewhat bulky, taking up a volume similar to that of a fist near the rear-view mirror on the interior of the vehicle. Additionally, the accuracy, while improved, could still be enhanced further. One alternative method to detect the presence of water on a windshield is theuse of capacitive-sensing technology. Capacitive sensors are used in a variety of products and applications today, including popular items such as the iPod, where the familiar “scroll-wheel” is in fact a series of capacitive sensors arranged in a circular pattern. Most modern touch-pads use capacitive sensing technology, including the Zune HD and iPod Touch MP3 players. Some appliances and products now use capacitive-sensors instead oftraditional buttons or switches. These sensors require no moving parts and can maintain a sleek, uninterrupted profile on a product. By itself, a capacitor is one of the most basic circuit elements used in all electronics, along with the inductor and resistor. Essentially, a capacitor can be thought of as two conductive plates, separated by a non-conductive material called a dielectric. When a voltage is applied to one plate, an electric field is created between the two plates, aided by the dielectric which has special properties to maximize the electric field strength in the gap, which holds a charge. The capacitors impedance, or resistance to the flow of current, is very large at low frequencies and DC and decreases as frequency goes up. It is thus often used as a filtering device in analog circuits, and as an integrator.
View Full Document
Unlocking...