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issue: May 2003 APPLIANCE Magazine

Report on Controls and Sensors
Function and Integration


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by Tim Somheil, Senior Editor/Manager of Electronic Media

The ongoing, innovative fusion of controls and sensors technologies makes the options for appliances control systems increasingly complex—and expands the potential for cost-savings and product differentiation.

The toothbrush turns on. The toothbrush turns off. How can you improve on a control like as that?

Today's aggressive suppliers of sensors and controls might come up with a dozen ways of making that simple On-Off component better.

For example, MEDER electronic Inc. (Mashpee MA, U.S.). saw plenty of room for improvement in the simple slide switch often used in this application. Such a control, the company points out, has the potential to become contaminated quickly and ultimately corrode. After all, a toothbrush may be exposed to acidic human saliva, alkaline toothpaste, and water temperature extremes. Corrosion may cause faulty switching, resulting in a dissatisfied customers. After all, most users expect their electric toothbrushes to last for years.

MEDER notes that hermetically sealing the slide switch can be an expensive solution, explaining that the reed switch/magnet combination is being recognized more as an option in such applications. This control uses a magnet molded into a plastic sliding configuration. Sealed inside the electric toothbrush, mounted on a p.c. board, the reed switch senses the position of the magnet. This provides a sealed control system that enables a toothbrush to operate for years, just as the consumer expects it will.


Picture a flat ceramic cooktop that senses when liquids boil over and in response reduces or turns off the heat automatically. That's a potential application with the MC 33974 electric field image sensing IC from Motorola (Austin, TX, U.S.). the IC generates and detects a low-level electric field and powers and supports a microcontroller unit (MCU), all in a single chip. It is designed to replace numerous discrete devices previously needed to achieve the same functionality. Target applications of the IC (imaging sensor) include appliances, machine tools, and virtually any other product or system that uses touch panel inputs as a user interface. Motorola says applications such as liquid level detection, spill detection, or moisture sensing would be simple to implement.


Cost Concerns

Distress in the global economy has increased cost pressures on the appliance industry. Recent years have seen costs, always a high priority, become even more of a focus for the industry, and that naturally cascades down to suppliers.

“Yet at the same time appliance makers are requiring their components to be continually improved in terms of performance, reliability, and space savings. Sometimes it’s a trade-off,” says Gordon Swanson, controls engineering manager for Kidde-Fenwal in Ashland, MA, U.S.

There’s also the problem of heightening buyer expectations. Consumers see their PCs and their mobile phones come down in price and expand their capabilities every year, and expect appliances to do the same.

“Consumers are very savvy and demand more features at a reduced cost,” says Stephen Caldwell, director of the Home Appliance Solutions Group for Microchip Technology (Chandler, AZ, U.S.).

In the controls arena, the costs per component are indeed coming down even as the technology grows more sophisticated. This is especially true in the electronic controls arena, notes Mr. Swanson of Kidde-Fenwal. “Not only is the per-part cost dropping, but so are the indirect costs—as an appliance company can save significant support expense by using digital technology instead of analog.”


MEDER electronic’s reed switch/magnet combination uses a magnet molded into a plastic slide to actuate a reed switch, mounted on a p.c. board sealed inside the toothbrush. MEDER says its SMD Reed Sensors, such as models MK15, MK16, MK17, are preferred for this type of sealed application.

Appliance OEMs are saving costs by doing less of the design work themselves. Mertik Maxitrol (Southfield, MI, U.S.) Managing Director Larry C. Koskela says, “OEMs are generally shifting design and engineering responsibilities (opportunities) to suppliers, as they streamline staff to reduce their costs. This creates opportunities and is an investment for suppliers that requires a return.”

When the controls and sensors supplier becomes responsible for providing a controls solution, rather than providing a specific component, a window of opportunity opens for using new configurations that increase capabilities and save costs, which can sometimes even be calculated across several appliance models. More appliance companies put increased significance on the ability to leverage design commonalty to achieve reduced control and sensor part numbers in their inventory.

“We at MEDER see it as a growing priority; however, only if it does not compromise functionality,” says John Beigel, MEDER president and CEO. “Obviously for the end user, the greater commonalty he can achieve, the better he is able to take advantage of supplier manufacturing efficiencies to reduce cost.”

Peter Buesch of Intercontrol (Nuremberg, Germany) says he sees some customers interested in using combined systems in order to reduce their overall costs, but believes this strategy is mostly for the largest, most international player in the appliance industry.


The D6A filter sensor contains a microprocessor with complex algorithms that provide a temperature reference point used to determine if a filter fan is moving the correct amount of air. Omron Electronics LLC of Schaumburg, IL, U.S. said it is the first sensor of its kind. If the sensor indicates that the airflow is at unacceptable levels, it can alert the user that the filter is clogged. This capability allows the sensor to help protect expensive equipment from breakdowns resulting from clogged filters. The temperature range of the filter sensor is 0°C to 45°C and its supply voltage is d.c. 12 V +/-10 percent. Its current consumption maximum is 60 mA and output voltage is 0-5 V. Potential applications include machines using a filter fan, such as cash registers, servers, and uninterruptible power supplies.

Electronics for Commonality

The inherent versatility of electronic controls, stemming from their programmability, makes them conducive to design commonalty.

“Fenwal employs a microprocessor-based platform that allows rapid control customization by changing software algorithms rather than by developing new circuits,” points out Mr. Swanson.

To make controls specification even easier and faster, Fenwal maintains an inventory of fully assembled controls that can be coded on command to match a customer’s application needs. “With the elimination of hardware manufacturing lead times, an application-specific control can be brought to market very quickly,” Mr. Swanson says. “By offering a wide range of timing and wiring options, we are able to respond to the level of customization demanded by appliance makers.”

Mr. Koskela sees a great deal of interest by OEMs in limiting not just the number of parts they use, but the number of suppliers as well. “Hence, the use of common components platforms is very desirable,” he explains. “It is a strong consideration for our own product development activities as we try to secure business with our OEM customers.”


MTS of Cary, NC, U.S., supplies sensors based on a continuous level sensing technology called SEF (Shaped Electromagnetic Field). The sensors offer an alternative to resistive float and arm devices. SEF-based sensors offer floatless operation and absolute measurement while taking up less space, and they are said to do so at a cost parity in volume. SEF technology sensors can be shaped to linearize the volume output in tanks with non-uniform, irregular cross sectional areas as the level rises.

They can also be shaped to fit into serpentine paths. Current sensor models are flat, roughly in the shape of a small ruler, but round models are also feasible. Non-invasive external mounting is also possible for use in plastic tanks. This level sensing technology has applications potential in medical systems, monitoring medications, and therapy fluids. It can measure water levels in appliances and food and drink systems.


 

The ever-expanding capabilities of electronics at lower price points makes them more attractive for achieving space savings, more precise measurements, additional features, and sometimes for quality and reliability advantages.

“Mechatronics can be defined as using electronics to accomplish tasks that traditionally have been done by mechanical solutions or by integrating the electronics into the mechanical component,” says Mr. Caldwell of Microchip Technology. “The objective of mechatronics is to achieve an advantage for the consumer or appliance OEM at the same or lower costs.”

For example, eliminating wires and other cost savings can be realized by putting electronics inside a switch instead of having a separate board, Mr. Caldwell explains, adding, “Secondary benefits include better reliability and a smaller footprint.”


Mertik Maxitrol’s new e-flame is a radio frequency-operated, battery-powered remote ignition and control system. The e-flame Remote Electronic Ignition System, Model GV60, consists of a combination control, a receiver, and a remote handset.


Configurable Electromechanicals


Still, the demise of the electromechanical controls has never been less likely—for so many applications they remain the best possible solution.

“We notice that the trend is: electronic controls if applicable and required and electromechanical controls in cases of cost reduction,” observes Mr. Buesch of Intercontrol. He adds, however, that there is much room for innovation in electromechanical controls by creating systems with a higher degree of component integration and expanded functionality.

Innovative designs are also making controls more configurable, further extending their range of usability.

“They will continue to be widely used for applications that need to sense a high temperature limit or require agency approvals,” Mr. Swanson of Kidde-Fenwal says. “Although some electronic controls are now entering the market at attractive price points—compared to their mechanical counterparts—there are applications where mechanical controls are the most cost-effective.”

Miniaturization techniques are helping to make them attractive in some applications.
“Reed sensors are becoming smaller and smaller with longer and longer service life. MEMS devices are being used when extremely small space is required,” says Mr. Beigel of MEDER. “All these factors create different opportunities, especially in the appliance industry.”

Electronics and electromechanical controls and sensors are increasingly being called on to work together. Many OEMs are requiring an interface capability between mechanical valves and electronics from their suppliers.

“The advent of building management systems and energy management systems is making a large impact on the necessity of electronics and mechanical valve interfaces,” says Mr. Koskela of Mertik Maxitrol.


Fenwal’s 35 Series control integrates two functions: hot surface ignition with precise temperature control. It can be configured for applications such as water heaters, commercial boilers, pool and spa heaters, and cooking appliances.



Functional Integration

When integrated control systems come into play, the electronic vs. electromechanical decision becomes a non-issue. An integrated system is designed using whatever components are best for achieving the overall solution. Hybrid controls sometimes offer the best of both worlds.

Karl Renau, president of Renau Electronic Laboratories in Chatsworth, CA, U.S., sees great potential in hybrids. The company makes hybrid digital controllers used extensively in institutional appliances such as washing machines, boilers, fryers, and coffeemakers.

“In April of 2003 we brought our new hybrid digital thermostat to the market,” Mr. Renau says. “It is a control designed to replace the mechanical thermostat in a number of applications such as we currently serve.”

Calling its controls hybrids means Renau married elements of electromechanical controls and solid state components, forming a single control. “The advantage we get with this hybrid design is extreme durability,” Mr. Renau explains. “We estimate this design extends the life of the control 10 times compared to a mechanical control.”

This high level of durability is achieved even in the controls’ harsh operating environments, fascinated by fully encapsulating it. Other significant advantages are cost savings and reduced size, Mr. Renau says.

One of Renau’s appliance industry customers has used a high-durability Renau control for some time. The control unit was made up of several components combined and Conforma-coated for extra resistance to harsh environments.

Today, the appliance producer uses Renau’s hybrid control, which has been compressed into about one-third the size of the previous unit. The new component, which controls the entire appliance, costs about half as much as the previous unit.
Another advantage of the Renau hybrid is its flexibility. Like an electronic control, it can be programmed to accommodate new applications, so an OEM can use a single component for a variety of appliance designs.

“Hybrids are not used that much, yet,” says Mr. Renau. “With these cost and durability advantages, I think hybrids represent the future of controls in many applications.”

The future means increasingly sophisticated electronics, an array of new controls and sensors technologies, and the reinvigoration of traditional electromechanical components through innovative reconfiguration and integration. To the appliance producer, this might translate into a more complicated specification process.
On the other hand, OEMs who find themselves partnered with the right supplier may find themselves with less costly, more capable controls solutions.


Setra Systems, Inc. of Boxborough, MA, U.S., added a 24 V a.c. excitation to its Model 265 Series of differential pressure transducers and transmitters for HVAC system manufacturers, designed to reduce installation costs while increasing overall operating efficiency. The transducers offer +/-1 percent full scale accuracy, with optional accuracy of +/-0.5 percent, +/- 0.4 percent, +/-0.25 percent. The Model 265 is designed for superior positive and negative pressure sensing, as is required for high-efficiency air control systems. The unit detects pressure ranges as low as 0.25 in up to 100-in of water column full scale, with 10 PSI overpressure on all ranges. It can also be configured with a choice of voltage output (0-5 V d.c. or 0-10 V d.c.) or current output (4-20 mA), and 12 or 24 V d.c. (nominal) excitation.


The Technology Acceleration

Kidde-Fenwal has witnessed an acceleration of microprocessor technology being incorporated into today’s newest appliances. "Perhaps as much as 50 percent of the applications Fenwal is looking at are ones that have become possible only because of technology that has been developed within the past 2 years," says Gordon Swanson, controls engineering manager, Kidde-Fenwal.

"Fenwal recently introduced a digital temperature controller platform which has been designed for flexible manufacturing," he says. "Configuration is quicker and simpler than with other digital controls and can be accomplished during the manufacturing process."

Fenwal is also looking at the continuing innovations occurring in the communications capability of temperature controls. In many industries, such as cooking, refrigeration, and pharmaceutical, data integrity is a concern. Mr. Swanson says that many controls coming from disparate manufacturers will soon be able to communicate with each other, making data more manageable.

 

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