a Southampton, UK-based semiconductor firm, produces
capacitive sensor ICs based on its patented QProx
Charge-Transfer Sensing technology. The company
reports that its solutions allow clients to create
stylish and robust touch controls. Pictured is
a board that was done for a Korean appliance OEM,
contracting to a U.S. company. The board is curved,
which is said to be a difficult task with membrane
One area of change
is the increasing use of digital technology in appliances. "There's been a big changeover to digital appliances," points
out Mike O'Brien, switches marketing manager at Omron
Electronics, LLC, (Schaumburg, IL, U.S.). "Digital
appliances require switches for extremely low loads and high levels
Yas Sasao, director of the Alps
Electric (USA), Inc., business unit in San Jose, CA, U.S. observes that the adoption rate of digital technology varies from region to region, with Asia and Europe farther along than the U.S. He notes that about 80 percent of washers in Japan use microprocessors and membrane switches, a much higher percentage than in the U.S., although digital is still growing there.
In ovens and ranges,
he points out, digital controls provide more accurate temperatures. "But the U.S. consumer is not so concerned with this," Mr. Sasao says. "They
are more price sensitive and not as impressed with digital advantages
as, for instance, are European consumers. Some appliance companies
may consider presenting traditional controls on the outside, but incorporating
digital on the inside."
Overall, many suppliers
are seeing a mix of requirements from customers. "On user interfaces, appliance companies demand everything from the traditional switches with tactile feel to solid-state switching applications," observes Doug Williams, business unit manager at Marquardt
Switches, Inc. (Cazenovia, NY, U.S.). "They
have the flexibility to select not only what solves their switch needs,
but also what addresses the look and feel they want to achieve. Internal
switch systems incorporate more sensors and integration as appliance
companies work to optimize performance while minimizing costs."
Achieving the Optimum
ultra-small space requirements, Selco
Products (Anaheim, CA, U.S.) has introduced the LSMC Micro
Series of temperature probes. Applications include specialized
needs of the medical industry. The thermistors, just 0.0185-in
diam (LSMC 400 Series) can fit into a thin hypodermic needle,
demonstrating the versatility allowed through miniaturized
How does an appliance
company achieve the optimum switch solution? "We have been able to provide savings to customers by being involved in the process early, while at the same time, providing unique solutions to meeting aesthetic requirements," says Al Hollenbeck, technical director, Poly-Flex Circuits (Cranston, RI, U.S.). "But
many times customers provide us with completed drawings, where it is too
late to integrate new ideas or make modest changes to improve design-for-manufacturing,
therefore, lowering the cost."
It is also important
to focus on electrical load and discuss it in detail. Steve Hugener, marketing
Electrical Products (Pleasant Prairie, WI, U.S.) points out that
occasionally, appliance companies design a switch based solely on its catalog
ratings. "For example, it might seem reasonable to assume that a switch rated at 10 A maximum should also work fine at 50 mA, but this is not always the case," he explains. "Switch
manufacturers can help steer OEMs around those potential pitfalls.
"The nuances of switch performance can also result in a lot of pain for OEMs that drive their sourcing through reverse auctions or similar processes," Mr. Hugener continues. "Switches
often appear to be easily cross-referenced commodities, but subtle differences
between manufacturers' products can make the difference between success and
failure in the customer's application."
John Cotton, sales manager
USA, Inc. (Vernon Hills, IL, U.S.), advises that when selecting
a switch, an appliance company should know the current and voltage the switch
is being asked to make and break. "Silver and silver-cad contacts are the materials of choice for 1 A, 2 A, 5 A, and 10 A," Mr. Cotton explains. "Gold
contracts rated for 0.1 A @ 125 V a.c. are required for dry-circuit switching.
Too often we find people overlooking the need for gold contacts in dry-circuit
Because of today's greater
focus on energy conservation, temperature control is especially important
appliance applications. As a result, Ron Buchanan, executive vice president
Company (Brandford, CT, U.S.), says his company is seeing higher
levels of interest in thermocouple and RTD designs for commercial appliances.
One approach his company takes is to add a temperature sensor into a liquid-level
switch design. "That would be either a thermocouple or an RTD sensor," he says. "The
advantage of the 'combo' switch is that the appliance can now monitor two
conditions, and the mounting design/hardware cost is reduced from two devices
to one combo device."
While customization may
be the ideal way to optimize a switch, this is not always a practical avenue
smaller manufacturers. "These [manufacturers] have historically been forced to use standard products or pay huge R&D costs for custom products," says Mr. Williams of Marquardt. "Being
a local supplier to companies on a global basis means we can utilize local
design resources to develop a solution and then tap into our global manufacturing
base to manufacture their products at a competitive cost. We have embraced
design and manufacturing principles like JIT and One Piece Flow that allow
for customization on a smaller scale."
In some cases, arriving at the optimum switch solution means going beyond the switch itself and offering value-added services, such as switch assemblies. For instance, Toneluck
Micro (Hong Kong, China) reports that it previously sold a microswitch to a water heater manufacturer in Europe. The appliance producer then assembled the microswitch into a complete pressure switch. Today, Toneluck makes the microswitch, builds the complete pressure switch, and calibrates it according to the appliance producer's specifications. This approach reportedly brings total cost down 30 percent by integrating all of these assembly processes.
Another application was
a project with GE Consumer & Industrial (Louisville, KY, U.S.). Initially,
Toneluck Micro provided just the microswitch for one of the control modules
a washing product. However, the supplier also had capabilities in tooling
and plastic parts. After assessing these capabilities, GE decided it wanted
the supplier to build the whole module with the microswitch assembled rather
than supplying the switch alone to a sub-contractor for assembly. The sub-contractor
had to buy other plastic parts from another injection house. Toneluck Micro's
tool engineers worked closely with GE's design and manufacturing experts,
and the result reportedly gave better value and savings since fewer parties
Increasing Safety Standards
A high level of customer
safety continues to be a goal in switches. "In years past, the major emphasis of manufacturers was to provide products to consumers that would be considered safe if the various types of protection devices incorporated into an application would function if the end application was in a fault condition," says Brandon L. Wehl, president and CEO of Portage
Electric Products Inc. (North Canton, OH, U.S.). "Basically,
you were more interested in keeping the entire application from causing other
problems for the consumer rather than protecting the consumer from themselves.
Today, dual-function protection devices are now being used in many applications
to not only protect the application in a fault or misuse situation, but they
also protect consumers, who believe they can fix whatever is wrong."
One such device is a self-hold thermal control. These incorporate some type of resistive heat source along with the functionality of a thermal-control-switching device to provide an extra level of consumer protection. With Portage's Model J(S) Series, should the device function due to a fault condition or misuse by the end user, then the thermal control portion of the switching device effectively opens the electrical circuit, turning off the power to the application. The resistive heat source is energized, creating enough heat to prevent the thermal control portion of the switching device from automatically closing and turning the power on to the application. The only way to reset the device is to interrupt the power from the source or pull the plug from the electrical outlet. Once the power has been interrupted, the resistive heat source no longer provides heat and permits the entire device to cool prior to resetting.
"This type of dual-function device is especially good for food blenders and food processors," Mr. Wehl says. "By
adding a second level of protection, you now are able to protect the consumer,
who might try to rectify the problem while the main power switch is still
on or the device is plugged into an electrical outlet."
One interesting development informs consumers that a particular safety device is included in their appliances. This is taking place in kettles that include control systems provided by Strix
Ltd. (Ronaldsway, Isle of Man, UK). Packaging for kettles from Birming-ham-based Team International carry a hologram label in a prominent position. The hologram indicates that a Strix control system, which complies with British and international safety standards, is included. The hologram is said to be very difficult to duplicate and distribution of the label is controlled by the switch company so only authorized manufacturers can use them. The label is said to be a response to counterfeit or illegal controls.
Many manufacturers strive to meet not just regional, but worldwide test requirements for switches. Amr Khalil, product specialist at Aromat
Corporation (New Providence, NJ, U.S.) adds that there has been a greater push to meet European test requirements such as VDE and TUV ratings. His company and parent company Matsushita Electric Works have invested a significant amount of effort to meet these standards. Now, all switches provided by Matsushita Electric Works and its subsidiaries are certified to worldwide standards, including UL, CSA, VDE, TUV, and SEMKO.
One potentially useful
standards development is that UL and VDE have agreed to adopt a harmonized
for switches, and UL has established clear phase-outs for existing UL 1054
standards, about 10 years in the future. Mr. Hugener of Cherry observes: "Over
the years, the differences in UL and VDE standards have contributed to some
divergence of Cherry's product lines, with certain switches ideal for U.S.
applications and other switches ideal for European applications. The upcoming
harmonization should enable us to converge these products and offer more
globally standardized switches."
Also on the standards
front, there is a new version of a regulation, valid in Europe, which describes
requirements for appliances and their components. "Under this regulation, called EN 60335-1, the appliance industry will be confronted with much sharper regulations concerning flammability of switches, tested by a glow-wire test," observes Anton Hartmann, sales manager of Switches & Controls for Cherry GmbH (Auerbach/Opf, Germany). "Our
D4 series does have a recently introduced material that already fulfills
the new rules that become effective in 2008. Designing in switches that meet
the standards now helps our customers prevent headaches in the future."
In touch-panel applications, Marty Hedrich, president and CEO of Monopanel
Technologies, Inc. (West Allis, WI, U.S.) reports that the requirements for tactile feel continue. This, he says, is achieved through the use of metal domes or other means of achieving a firm response to switch closure. This would include the use of discrete switches underneath an overlay.
"The improvements in performance, size, and price make it more attractive to embed LEDs in flex membrane switches and achieve the economics and features of both tactile and visual feedback of switch closure," Mr.
Hedrich says. For harsh environments, his company's Endura product line
uses a patented membrane switch that can be operated through .031 thick
aluminum and up to .060 thick polycarbonate. It is specified for such products
as commercial washers and dryers, scales, gas dispensing equipment, and
other applications with harsh and abusive environments.
One alternative to membrane and mechanical keypad offerings uses piezo technology. Barantec, Inc. (Clifton, NJ, U.S.), a subsidiary of the Baran Group, reports that its patented technology is rugged, with no moving parts to ensure a zero-failure rate. A unit is a totally sealed one-piece construction, allowing it to operate in harsh environments and in high-usage areas. The switch is behind a metal layer. The piezo switch measures force - the actual deflection of the metal. It is not a capacitive switch, which senses a finger on the metal but does not work as well when someone is using gloves.
One principle behind
the Baran piezo technology is the assembly of all the necessary components
single unit (the module), thus eliminating the need for handling every component
for each push point manufactured. "Understand that the module is the technology behind all of our products," says Ayal Vogel, president of Barantec. "This
makes it very universal and gives the industrial designers the ability to
make sexy products without sacrificing any durability. In addition, our
switches are non-mechanical and do not require any power. With these switches,
the appliance industry benefits from easy cleaning, lower service costs,
and reduced maintenance."
Switches and Sensing
Sensors are playing a
larger role in appliance switching. Energy efficiency, water conservation,
performance are driving the increased need to provide feedback for advanced
control algorithms, says Mr. Williams of Marquardt Switches. "We have expanded our technology base to include sensor solutions to provide flow, turbidity, pressure, vibration, and other key measurement input," he
One development for vacuum
cleaners is an Automatic Speed Adjuster (ASA) from Kurz
U.S.A. L.L.C. (Sarasota,
U.S.). This monitors vacuum cleaner suction power based on the type of surface
being cleaned. Thus, there is less power when vacuuming carpets and more
power when vacuuming hard floors, enabling users to clean hard-to-get, deeply
embedded dirt in small cracks and gaps. "The ASA consists of a pressure switch mounted on an electronic control," explains Heinz Kutschera, president of Kurz. "It's being used by such companies as Miele, Electrolux, and BSH Bosch und Siemens Hausgeräte."
OH, U.S.) has taken its knowledge of temperature switching and applied it
to liquid-level sensing and flow sensing. "Our level sensor uses one or more thermocouples to sense level, and we have developed a flow sensor using a specially packaged thermistor and some proprietary software," says Martin Leslie, product manager. "The
effect of both technologies is that we can sense level or flow rate with
no moving parts."
The company has also
developed products that combine its bimetal thermostats and packaged thermistor
into one package "to bring added value to customers," Mr. Leslie notes. "We
are also in development of a polymer-based product that, instead of switching
in response to temperature, switches in response to certain vapor in the
air, hence providing a vapor sensor to our customers. All three items are
proven technologies right now. We plan to be selling actual products based
on these technologies in the near future."
Whether it is new technologies like these or tried-and-true solutions, look to your suppliers to show you how to push the right switch buttons for your appliances.