Appliance Design - August 2007 - (Page 16)

SWITCHES & RELAYS A strawberry drawfs this reed switch from Meder. Reed switches such as these from Hasco come in a variety of bent configurations. are used to control the various power settings for stovetop burners. The sensor eliminates the need for knobs, electronic gadgetry and Hall effect sensors; the latter two of which require added power and additional circuitry. On the surface of the oven and near one of the elements, a sliding device with an integrated magnet is installed. Reed switches are mounted just below the surface. As the sliding device is moved, it triggers the various reed switches, which in turn will activate different power settings. One of the most common applications for a reed switch is in the form of a reed relay, which is made from a reed switch with a coil wrapped around it. When a current is sent through the coil, it becomes magnetized and the reed switch closes. According to Hauser, the reed switch is usually molded in a single in line (SIP) or dual in line package (DIP), and is very fast. Hauser, whose company offers reed relays in versions including DIP, SIP, RRH and mini-reeds, says the relays can operate at speeds of 0.3 milliseconds, and can handle switching current from 0.3A to 1A and carrying current from 0.5A to 2.5A. Reed relays are also available for PC boards. (A carry current is the maximum current that can be applied to an already closed contact. The switch current is the maximum current a reed contact can switch.) Meder Electronic recently released its RM series of reed relays that features a low-profile module having three input-output options — four inputs with four, two and 1 outputs — and is capable of switching beyond 3 GHz with <40 ps rise time. Another company with a new reed relay product is Warwick, R.I.-based Coto Technology that offers reed relays that are capable of carrying up to 6 amps. The relays can provide switching current up to 4 amps along with 10-15 KV switching. One of the company’s newest products is the Coto RI90 Series with a 15 mm maximum glass length, which is a single-pole double-throw type, having three contacts: a common contact, a normally-open contact and a normally-closed contact. When brought in the proximity of a magnetic field, the common contact will first open with normally closed contact, and then make contact with the normally open contact as long as the magnetic field is applied. Trial and error Selecting the right reed switch for the job can be a matter of trial and error, says Hauser. The correct length, amp draw, air gap and sensitivity, mounting requirements and other factors all come into place. “It isn’t like a toggle switch,” he says, “the engineers of both Hasco (and other vendors) and the end customer can work together for days, weeks and months, depending on the complexity of the design,” says Hauser. For one customer, it took months to develop the reed switch. It is not only choosing the correct reed switch that is important, but also deter- mining the correct actuating positions. Berns says that there are several standard and recommended actuating positions and many alternative positions. These may include an actuating position for a perpendicular motion in which the switch only closes once with each magnet pass, keeping the switch closed for the maximum magnet travel. Another alternative is a parallel motion that provides as many as three closures with the maximum magnet travel, but can provide only one closure with restricted movement. A front-to-back motion is similar to parallel motion, except that the motion is at right angles to the switch and it completely passes by the switch. “The applications can be like art in a way,” says Berns. “Sometimes people will come to us with an application and nobody makes anything that will work. And we will help them develop a reed switch and magnet for the application.” < For more information, enter numbers: Coto Technology. . . . . . . . . . . . . . . . . . . . . . . 300 Or email: sales@cotorelay.com Hamlin Electronics . . . . . . . . . . . . . . . . . . . . . 301 Or email: simon.pitkin@hamlin.com Hasco Components. . . . . . . . . . . . . . . . . . . . . 302 Or email: tabh@hascorelays.com MEDER Electronic . . . . . . . . . . . . . . . . . . . . . 303 Oe Email: rgreenberg@meder.com Reed Switch Developments . . . . . . . . . . . . . . 304 Or email: rberns@reedswitchdevelopments.com 16 applianceDESIGN August 2007 www.applianceDESIGN.com http://www.appliancedesign.com

Table of Contents Feed for the Digital Edition of Appliance Design - August 2007

Contents Editorial Shipments/Forecasts News Watch A Reed Switch is Simople, yet Versatile, and Designers are Finding New Uses for this Time-Tested Technology A Novel Actuation and Sensing Technology can Register a Light Touch, but Resist Blows from a Hammer Tracing the Source of Noise is Made Easier with Noise Source Identification Methods Appliance Noise can be Annoying, but Designers have Many Material Choices to Help Rein in the Racket Nanocomposites are No Longer a Technology for the Future. These Plastic Materials are Already on the Job A New High-Strength, Low-Density Glass-Microsphere Additive can Improve Plastic Part and Molding Performance A New Electromagnetic Weld/Bonding Process Helps Ensure Long-Term Integrity of Joints in Plastic Parts Snap-Based Technology Eases Installation and Makes Products More Serviceable Two-Part Silicone Adhesives Provide a Rapid-Cure Alternative to Traditional One-Part Silicones Classified DesignMart Advertiser’s Index Association Report: GAMA

Appliance Design - August 2007

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