Appliance Design - March 2009 - (Page 30)

SWITCHES & RELAYS Contactless Actuation Hall-effect sensors provide a reliable, durable switching alternative. D by michael doogue Michael Doogue is director of strategic marketing/systems engineering, Sensor Business Unit, Allegro MicroSystems, Worcester, Mass. 30 applianceDESIGN March 2009 espite the fact that Edwin Hall discovered the Hall effect in 1879, readily available and cost effective Hall-effect sensors would not surface in the marketplace until the later part of the 20th century. The rapid development and expansion of silicon integrated circuit (IC) manufacturing technologies in the 1970s essentially enabled the modern day Hall-effect sensor. And in recent years, as Hall sensor technology evolves to an even higher level of integration, the popularity of Hall effect sensors is on the rise in appliance design applications. The Hall effect refers to the measurable voltage that appears across a conductive material, for example silicon (Si), when an electric current flowing through the conductor is influenced by a magnetic field. Under these conditions a transverse voltage is generated due to the balancing of the Lorentz and electromagnetic forces. In simple terms, a Hall-effect transducer creates a differential Hall voltage that is proportional to the perpendicular component of an applied magnetic field. The fact that silicon can be used to create an accurate and effective Hall-effect transducer yields substantial benefits. First and foremost, the use of silicon wafers allows for economical and effective integration of various signal-processing circuits on a single silicon die or substrate. (See Fig. 1.) The integration of the Hall-effect transducer, chopper-stabilized amplifiers, filters, comparator circuits, and complex logic functions allows for the creation of a vast array of highly accurate, reliable, application-specific Hall-sensor solutions. Advantages The contactless operation of Hall sensors improves system reliability and durabilwww.applianceDESIGN.com http://www.appliancedesign.com

Table of Contents Feed for the Digital Edition of Appliance Design - March 2009

Appliance Design - March 2009 Contents Editorial Shipments/Forecasts News Watch Transmitting Power Wirelessly Promises to Reduce the Ever-Growing Tangle of Cords and Cables Found in the Modern Home. There Are Different Technological Approaches for Achieving this Goal, and Some Are Already on the Market. Electrochemical Capacitors Can Provide an Extra Peak-Power Boost in Battery-Operated Appliances, Allowing Product Designs to Have Smaller Battery Packs. Metallic Foams Put the Properties of Metals into Lightweight Packages. Applications for this Emerging Technology Include Gas Burners, Heat Exchangers, and Electronics Housings. Hall-Effect Switches Are Compact and Provide a High Degree of Reliability and Durability as They Virtually Eliminate Mechanical Wear, Shock, and Contact Oxidation. Blowing Agents for Polyurethane Foam Insulation Face Increased Scrutiny Due to Global Warming Concerns, but Alternatives with Lower GWP Values May Provide Solutions to Meet These Challenges. Design Marts Association Report: AHAM Advertisers' Index

Appliance Design - March 2009

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