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issue: May 2007 APPLIANCE Magazine

Sensors and MCUs
A Cosmetic Approach to Controls

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by Jill Russell, Contributing Editor

Increased use of advanced sensors and microcontrollers is helping to change the old appliance "sea of white" into a sea of options.

Customized inGen Linear Direct sensors from InProx Sensors (Boston, Massachusetts, U.S.) have applications in cooking, laundry and dishwashers. The position measurement device has been used inside commercial ovens to provide temperature operability to 450°C. The sensor can be flush mounted within the oven’s inner cavity and detect a rack in any position for self-cleaning cycles. The sensor also offers a color matching ability that will match up sensors with the specific coloration and texture of any oven cavity wall. In laundry applications, the sensors monitor acceleration, velocity, balance, and weight measurements. The company says that in comparison with motor feedback, accelerometers, Hall-effect and VR technology, its sensors provide higher accuracy, with error-free and temperature drift-free measurements, in a digital package.

The fact that sensors and microcontrollers (MCUs) have allowed appliance makers the ability to build more functions, settings and operating modes into their products is nothing new. The integration of advanced electronics enables much of the convenience consumers enjoy today.

But as sensing and control technologies advance and evolve into the “electronic brain” of modern appliances, those appliances are reaching new levels of sophistication and capability.

Advanced sensors and controls are helping to make more appliances “smart”—capable of self-monitoring and self-protection. In addition, sensors and controls are used more in displays and touch pads to truly integrate function with the cosmetic appeal of a product.

“Appliance makers are continually looking at controls to add differentiation in terms of cosmetics as well as function,” says Cliff Ortmeyer, market development manger, Appliance Sector of STMicroelectronics’ (Geneva, Switzerland) Worldwide Competence Center. In response, suppliers are creating more reliable and integrated solutions that help reduce costs. This, according to Ortmeyer, is enabling more sophisticated sensor and MCU options, once typically only found on high-end appliances, to enter the mid-line appliance market.

Sensors and controls are evolving into interactive displays, bringing new aesthetics possibilities to appliances—and with it comes product differentiation.

Sensible Software

Schott HomeTech North America, Inc. is just one company utilizing advanced technology in its control designs, and is doing so with embedded software. The company recently introduced its Schott Commander, a cooktop touch control that is available as an off-the-shelf component. It allows any appliance maker to customize the electronic controls under the glass with the use of software.

Ken Such, general manager of Electronic Controls for the Louisville, Kentucky, U.S.-based company, says that as appliance OEMs demand more economical controls on a shortened timeline, software and design modules allow suppliers to fine-tune their areas of expertise, and offer advanced solutions.

“Appliance makers continue to want controls developed faster, (that are) more economical and of higher quality while at the same time being smaller, more powerful, more efficient, and (that produce) less noise,” he explains.

Schott addressed those needs in its Commander, a one- to four-burner induction cooktop. The company’s embedded software design group uses a rapid prototyping methodology that considers graphic user interface (GUI) behavior and OEM requirements early on in the design phase. The GUI and control software are then designed on a PC. Schott says this approach enables appliance makers to make changes to the GUI without it affecting software quality.

“This type of application programming implies a higher level of responsibility than just writing embedded software, since it acts as an interactive requirements specification,” Such tells APPLIANCE. “Software code written for the virtual design can be recompiled for the final embedded microcontroller so that the programmer maintains only one version of the appliance controller. This style of programming promotes software reusability and design clarity.”

It was this programming style that enables the system’s quick start-up functions and allows users to easily adjust burner temperature. The unit includes a timer and a safety lock feature. The cooktop was originally designed for the recreational vehicle market, but the supplier says it is versatile enough for the residential market and is an ideal solution for applications with space constraints. Schott says that this product-ready control can also add a unified look to a particular brand or product line, helping to answer OEMs calls for increased brand recognition and differentiation.

Amulet Technologies LLC (Santa Clara, California, U.S.) is also using sophisticated technology for its sensors and, ultimately, its GUIs. Amulet CEO Ken Klask says an increased focus on product differentiation is adding momentum to the sensor/GUI trend as this approach allows OEMs to not only increase product functionality, but also customize product look and feel.

“By using a display, appliance companies are able to differentiate themselves by incorporating graphics versus having very similar-looking buttons and LEDs on a crowded interface,” Klask says. “In the past, appliance functions were very similar, but today’s appliance controls have to be much more modern and sleek to set themselves apart from other brands. The concentration is on the look and feel of the brand and designing appliances within that particular brand to look alike and set themselves apart from competitors. Appliance manufacturers are pressured to make their products increasingly more functional, but they can only put so many push buttons and LEDs on the front before it starts looking like a light show or switch board.”

To avoid this, Amulet’s display technology places all product controls and functions in one place—on a touch panel display. This, the company says, provides a high level of function and sleek aesthetic in a single package. Amulet’s chip, which combines an LCD controller and MCU, is built using HTML and allows OEMs to add graphic-rich screens to add to product differentiation and increase brand recognition. This technology also allows OEMs to build user manuals or help menus into the display.

“There is a huge trend toward implementing GUIs,” Klask says. “If appliance companies are not currently thinking about, or designing in, display controls, this could set them apart from their innovative competitors in the near future.”

The trend to use GUIs may require more powerful processors (say to a 32-bit MCU from an 8-bit). This upgrade may lead to increased costs and possible software glitches. Amulet says its solution eliminates this as its software runs directly on the hardware, allowing it to run independently, as opposed to running with a host MCU acting as the workhorse. This method reduces the risk of system control failure and makes debugging in the design phase easier. Additionally, the display remains functional even if the appliance stops functioning, so it can be used to help diagnose the problem.

Quantum Research Group is also helping to provide touch-screen solutions with their capacitive sensors. Having already supplied a number of sensor/GUIs to well-known appliance makers such as Jenn-Air, GE and Whirlpool, the Southampton, United Kingdom-based company says this technology is gaining popularity as costs decline and consumers demand more advanced and better-looking appliances.

“Designers want more flexibility,” George East, product line manager for Quantum’s Exotic Product Division, says. “Something that will allow them to add a ‘wow’ factor. With capacitive sensing, you can create touch screens, soft keys, slider rotors, or buttons behind the glass or front panel, making the solution practically indestructible and easy to keep clean and maintain.”

The company recently released a 16- and 24-key touch sensor chip that is able to sense touch through any electrically insulating material of 50 mm or more. The chip operates on only 1.8 V DC. In addition to traditional white goods, it can be used in mobile phones, hand-held devices such as MP3 players and other consumer electronics. Part of the company’s QMatrix family, the chips overcome interference by utilizing a spread-spectrum modulation to reduce noise and emissions.

The iMotion sensorless sinusoidal motor control platform from International Rectifier (IR) (El Segundo, California, U.S.) consists of a mixed-signal controller, intelligent power module and analog interface. The platform is designed for systems using permanent magnet synchronous motors and is said to deliver quiet operation and increased efficiencies for variable speed pump applications by up to 50 percent. The platform is already seeing applications in washing machines.

A Simple Approach

Some companies are taking a different approach—a more simplified one. Microchip Technology Inc. (Chandler, Arizona, U.S.) says it’s taking a more efficient approach with its distributive intelligence technology. Using a limited amount of memory and IO capacity, Microchip is offering MCUs in a smaller package, and with a lower price tag, and they can be embedded into sensors.

“By using less material our customers can embed the MCU into the sensor and offer a more competitive solution. The main MCU is no longer ‘talking’ to the sensor; that is now done with a smaller, ‘distributed’ MCU,” Steve Caldwell, director of the Home Appliance Solutions Group for the company, explains. “Instead of the main MCU’s CPU being bogged down with multiple functions, each function can have its own individualized MCU, allowing it to work more efficiently.”

The six- and eight-pin miniature MCUs are available in a 2 mm by 3 mm package, requiring 30 percent less board space. They feature 16 to 41 bytes of data and an operating voltage range from 2 to 5.5 V.

Freescale Semiconductor (Austin, Texas, U.S.) is also taking a more simplified approach, but with a different methodology. The company is helping OEMs reuse existing designs and intelligent properties across several platforms, and customize features and product functionality without changing the printed circuit board.

“Freescale’s controller continuum strategy provides customers the flexibility to migrate between compatible 8- and 32-bit MCU product families,” Fraser McHenry, product marketing manager for Freescale’s Microcontroller Division, explains. “The products, being pin compatible, share the same peripherals and the same memory map. They use the same hardware and software development tools so designers can move seamlessly from an 8-bit solution to 32-bit if they need increased levels of performance.”

Up-and-Coming Applications

Appliance sensors and controls are also advancing by borrowing from other industries, including the automotive and aircraft arenas. Sensata Technologies, formerly the Sensors and Controls business of Texas Instruments, is working on several new appliance sensor applications, one stemming from an air quality sensor originally designed to detect volatile organic compounds (VOCs) in automobiles. The new unit can be used in refrigerators to detect and manage food odor or be used as a safety feature in gas-fired water heaters and furnaces.

The metal oxide technology works by detecting air and relating a concentration of a compound such as VOCs, NOx or carbon monoxide to a change in resistance, explains Charlie Douglas, business development manager of Control Products for the Attleboro, Massachusetts, U.S.-based company. U.S. legislation already requires water heaters to be Flammable Vapor Ignition Resistant (FVIR) certified. Douglas says that a similar gas oven standard is on the way and Sensata’s VOC sensor can help meet the regulations.

Another automotive sensor, this one used to gauge brake and tire pressures and weight loads, is finding its way to the appliance industry via laundry appliances. Sensata’s micro-fused strain gauge technology is beginning to arouse interest for load detection applications in washers and dryers.

Other pressure sensors may have applications in both residential and commercial air-conditioning units. Sensata’s 2CH line of case-isolated pressure sensors are said to overcome electromagnetic interference (EMI) barriers in commercial HVAC/R equipment. According to the company, the pressure transducers feature 100 V/m and a dielectric terminal-to-case strength of 1.8 k V AC.

The company’s pressure sensors are also seeing applications in residential HVAC systems. Douglas says the technology might also be applied to detect loss of charge and protect the system when a loss is detected. The ceramic capacitive hermetic sensor is also said to help monitor efficiency between the high and low end of the system and adjust it accordingly. Here, evaporator outlet pressure can be monitored by networking a pressure sensor into the central control unit.

The direct feedback, according to the company, allows an electronic expansion valve to accurately control the refrigerant going into the evaporator coil. According to Douglas, this type of application is already in production with several large HVAC manufacturers and is expected to trend upward as efficiency standards become more stringent.

Whatever the application, it is clear that advanced sensor technologies are not only changing the way appliances operate, but also how they look. The appliance showroom is changing from a “sea of white” into a sea of options with the help of advanced sensor and control alternatives. And as options increase, the cosmetic look of the appliance changes as well. Who knows what the future appliance will look or how it will perform. Only time and technology will tell.


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