Most Major Appliances Shipped Strong in March

The U.S. appliance industry showed healthy increases in March factory unit shipments in most of the appliance categories tracked by the Association of Home Appliance Manufacturers.

Shipments in the AHAM 6 category of appliances (washers, dryers, dishwashers, refrigerators, freezers, ranges, and ovens) were up 9.3% in March 2010. 4,015,300 units shipped, compared to 3,675,000 units shipped in March 2009. For the year-to-date, 9,054,900 appliances have shipped in the AHAM 6 category, up 5.5% from the 8,573,500 appliances shipped in the same time period in 2009.

Cooking appliances had another strong month in March with the ongoing exception of microwave ovens.
• Electric cooking (ranges, ovens, and cooktops) were up 7.1% in Mar. 2010 (450,800 units shipped) over Mar. 2009 (421,000 units shipped). Electric cooking is up 5.4% year-to-date.
• Gas cooking shipments (ranges, ovens, and cooktops) were up 14.6% in Mar. 2010 (278,900 units) over Mar. 2009 (243,300 units). Gas cooking is up 9.1% year-to-date.
• Microwave oven shipments were down 15.8% in Mar. 2010 (880,500 units) from Mar. 2009 (1,046,100 units). Microwaves are down 12.0% year-to-date.

Home laundry was up overall 2.1% in Mar. 2010 compared to Mar. 2009:
• Mar. 2010 washer shipments were up 2.0% to 882,300 units. Washers are just barely down year-to-date at 0.1%.
• Dryer shipments were up 2.1% in Mar. 2010 compared to Mar. 2009. Dryers are up 3.4% year-to-date.

The Kitchen Clean-Up category had a strong month thanks to big growth in built-in dishwasher shipments. Dishwashers were up 21.5% in Mar. 2010 (640,500 units) compared to Mar. 2009 (527,100 units).
• Built-in dishwasher shipments were up 21.9% in Mar. 2010 (633,200 units) compared to Mar. 2009 (519,500 units).
• Portable dishwashers were down 4.5% in Mar. 2010 to 7,300 units.
• Disposers fell 6.7% in Mar. 2010 (456,300 units shipped) compared to Mar. 2009 (489,100 units shipped). Disposers are down 1.1% year-to-date.
• Trash compactors turned in surprisingly strong growth in March, up 19.5% compared to Mar. 2009. Compactors remain down 9.8% year-to-date.

In the Food Preservation category 1,104,200 units were shipped in Mar. 2010, up 13.9% from 969,600 in Mar. 2009. The category is up 8.8% year-to-date.
• Refrigerators shipped 901,300 in Mar. 2010, up 16.2% from 775,500 in Mar. 2009. Refrigerators are up 12.1% year-to-date.
• Freezer shipments were 4.5% in Mar. 2010 (202,900 units) compared to Mar. 2009 (194,000 units). Freezers are, however, down 4.0% year-to-date.

In AHAM's Home Comfort category:
• Room air-conditioners shipments were down 21.4% in Mar. 2010 (1,069,000 units shipped) compared to Mar. 2009 (1,360,500 units shipped). Room air shipments are down 32.1% year-to-date.
• Dehumidifier shipments – which were down 56.6% in February – eked out 0.4% growth in Mar. 2010 at 255,900 units compared to Mar. 2009's 255,000 units. Dehumidifiers remain down 15.3% year-to-date.

AEG-Electrolux Microwave Relies on Low-Warpage Polymer

AEG-Electrolux relies on a special low-warpage grade of liquid crystalline polymer (LCP) to play a critical role in its combination ovens. Vectra liquid crystalline polymer (LCP) from Ticona Engineering Polymers provides heat resistance to an easy-to-clean interior door panel that covers a key metal component which, in turn, keeps microwaves inside the oven.

Vectra E440i is both heat resistant and transparent to microwaves and the material is used in an interior door panel where temperatures can reach up to 250°C. The injection molded panel permits electromagnetic energy to pass through to a hidden wave trap that prevents dangerous microwaves from escaping through the space between the metal frame of the door and the frame of the cooking space.

The material is also used because it offers stiffness and strength, scratch-resistance, and ease of cleaning.

The low-warpage LCP also offers easy and cost-effective thin-wall injection molding technology advantages due to excellent flowability. The 175-gram door interior panel is molded with a sprue of just 4 grams.

Tactile Pressure-Indicating Sensor Films

The Pressurex Zero is the newest addition to a firm’s tactile pressure-indicating sensor films. It characterizes tactile contact surface pressure down to an extremely low 7.2 psi. The easy-to-use flexible film is placed between contacting or mating surfaces to instantly and accurately map and measure pressure magnitude and distribution. Variations in contact surface pressure are immediately visible by the impression made on the film. The sensitivity of the film’s coating shows precisely how surfaces deform and engage under stress. The spatial resolution of the film is fine enough to expose minute surface defects and other imperfections. The range for Pressurex Zero is 7.2–28 psi. Sensor Products Inc., www.sensorprod.com

Web Exclusive: LCD Displays Withstand Extreme Temperatures

Optoelectronics specialist Lumex (Palatine, IL, U.S.; www.lumex.com) recently launched the InfoVue High/Low Temp series of custom, high-duty LCD displays for applications that perform in extreme heat or extreme cold. Whereas existing LCD technology performs in the –20° to 70°C temperature range, Lumex says, the InfoVue High/Low Temp displays provide consistent high-quality performance from –40° to 85°C.

“Previously LCDs that operated in extreme cold or extreme heat required bulky built-in heaters and coolers in order to ensure performance,” says Yasoob Ahmed, display technology manager. “The special liquid crystal used in the InfoVue High/Low Temp series eliminates the need for coolers and allows us to use low-power heaters.“ In addition, Ahmed says, custom InfoVue LCD displays can provide a 50% savings in technology costs and 80% energy savings when compared with alternative technologies such as vacuum fluorescents.

InfoVue LCD displays provide full graphic capability and daylight visibility. When combined with LED backlighting technology, a wide range of color options is available. Users can either opt for a monochromatic screen with any color of LED backlight, or select negative image option with mono colored pixels and a black background.

The displays can be produced in sizes ranging from 8 × 1 character displays to 320 × 240-pixel graphic displays.

An onboard LCD controller makes a new MCU series an affordable and flexible solution for design engineers

The latest addition to the R8C family of microcontrollers (MCUs), the R8C/Lx series from Renesas Technology America Inc. (San Jose, CA, U.S.; www.renesas.com) offers engineers a built-in LCD controller and is capable of driving up to 416 LCD segments. According to the company, these features, along with other integrated features such as power-on-reset and on-chip oscillators, create a single-chip solution that reduces bill of material costs and design complexity.

“Electronics in a typical home appliance have to perform three main functions: system control, user interface, and safety/monitoring,” explains Nelson Quintana, product manager, system LSI business unit. “The R8C/Lx MCU integrates functional blocks to handle all three tasks.”

The MCU’s peripheral functions such as A/D, D/A, timers, and serial interfaces can be used in system control. Similarly, specialized hardware features such as detection of oscillator failure, an independent watchdog timer, and protection of system registers provide a self-testing mechanism to achieve a high level of safety and reliability. For the user interface, the MCU can control the most common input devices such as key matrices or knobs, and it can drive an LCD glass to enhance the operation of the appliance.

Quintana says that compared with other design options, an MCU with a built-in LCD controller provides more design flexibility. “Products incorporating an LCD can be typically designed using standard I/Os from any MCUs. This approach, however, has many limitations in the type and/or size of LCD glass that can be controlled, and the design can be complex since it is a software-based approach,” he explains.

A second approach is to use an LCD module that has a dedicated controller, also known as chip-on-glass. “Although this may be the easiest way to add an LCD to a product, it is definitely not the lowest-cost solution because of the addition of an extra chip,” Quintana says. “An MCU with a built-in LCD controller such as the R8C/Lx series provides greater flexibility, because the hardware can be configured for various options, thus reducing the software complexity and eliminating the cost of external components.”

Further adding to the device’s flexibility is the integrated data transfer controller (DTC). “The DTC unit can be configured to move data from any location in memory to any peripherals or vice versa,” Quintana explains. “In addition, the unit can be set to start transfers immediately after an interrupt trigger or with software control.”

In a motor control application for a washing machine, which requires the MCU to continuously monitor motor sensors through multiple A/D inputs, Quintana says the DTC can be configured to automatically transfer the A/D conversion results from the A/D registers to RAM for calculation purposes. “By doing so, the CPU will not be interrupted; hence, reducing the interrupt handling overhead,” he says.

Based on a 16-bit CPU core, the new device also integrates data flash memory with a background operation function that allows the CPU to execute instructions while data are being written to or erased from the data flash. It supports an extended voltage range of 1.8 to 5.5 V to give system designers options for configuring their power supplies, while potentially reducing system cost by eliminating unnecessary components. In addition, high-speed on-chip oscillators eliminate the need for an external resonator by proving precise clock signals at 40, 36.864, or 32 MHz.

In addition to an integrated data transfer controller, data flash, and an onboard 416-pixel LCD controller, the R8C/Lx MCU features hardware for self-testing to facilitate industry standards for safety.

Digital Multitasking: Motor control and sensor processing handled by a single chip.

Appliance technology has evolved significantly over the years, and two trends are merging to fuel the next round of appliance evolution — digital motor control and digital sensor processing. Digital Signal Controllers (DSCs) are at the confluence of these trends, and enable digital sensor processing, digital motor control and power factor correction to be implemented on a single chip.

DSCs have hardware accommodation for efficient DSP processing on-chip. While many advanced sensorless algorithms do not require DSP, most benefit from on-chip DSP resources. For example, the highly efficient Field-Oriented Motor Control (FOC) algorithm benefits from a single-cycle MAC, accumulator saturation and other features common to DSPs and DSCs, but not typically found on MCUs.

While the real world is analog, digital techniques have progressively augmented traditional analog design implementations. At the point where the balance is tipped, where the digital approach cannot be effectively matched with analog wizardry, digital control and processing become mainstream tools in the designer’s tool bag.

Digital motor control

Enlarge this picture Fig. 1. Resource utilization for an advanced sensorless FOC algorithm on a 28-pin, 128 KB Flash DSC.

The ongoing trend toward electronic control is driving the venerable commutator out of its DC motor shell, as evidenced by the migration from Brushed to Brushless DC (BLDC) motors. Another disruptive shift was the replacement of Hall Effect sensors with resistor dividers to measure EMF feedback, through the main phase connections, to determine rotor position and velocity.

Now, advanced algorithms such as FOC are considered highly desirable, due to the resulting excellent torque response, improved motor efficiency and lower audible noise obtained through sinusoidal drives. The FOC algorithm asymptotically decouples the rotor torque and rotor flux, making the speed linearly related to torque current. This permits, for example, an induction motor to possess the same behavior of a separately excited DC motor.

All of these motor transformations have one thing in common: they are enabled by progressively more sophisticated electronic control, coupled with an economically viable control solution. The primary impediments delaying these dramatic shifts have been the availability of cost-effective control, and the time needed to understand and refine the technology.

Many underpinnings of those impediments have been removed with modern DSCs, which offer cost-optimized and application-optimized performance coupled with robust applications support. Regulatory add-ons, such as active power factor correction, exacerbate the control workload and accelerate acceptance of the digital solution. As DSCs continue to add capability and performance while prices continue to decrease, new possibilities for product development emerge. This can be illustrated with the example of the merging of digital motor control with digital sensor processing onto one DSC.

Digital sensor processing

Enlarge this picture Fig. 2. Sensor signal plus noise in the time domain.

Today, a sensor signal within a typical motor-driven appliance is filtered, level shifted, amplified and fed to the Analog-to-Digital Converter (ADC) of an embedded controller. The performance of the embedded application depends on accurate information coming from the sensor. Sensors can degrade with use, which may accelerate product failure. Analog-filter and gain characteristics can change over time, temperature and manufacturing variations.

Digital sensor processing can be employed to provide advanced compensation for a variety of sensor conditions, including sensor degradation, performance reductions in age-sensitive or temperature-sensitive components, failure prediction, substituting a less expensive sensor without performance loss, or improving sensor accuracy. Since DSCs are increasingly being used for motor control, they provide an opportunity to utilize excess resources to also handle digital sensor processing tasks. Fig. 1 illustrates the resource utilization for an advanced sensorless FOC algorithm on a 28-pin 128 KB Flash, the dsPIC33F128MC202 DSC. (Note: dsPIC is a registered trademark of Microchip Technology.)

There is richness to sensor data in the frequency domain that is not apparent in the time domain. Sensors are often remote from signal conditioning circuitry, and their signals are subject to environmentally induced noise. A low signal-to-noise ratio can adversely affect the performance of the end application.

Enlarge this picture Fig. 3. Sensor signal plus noise in the frequency domain.

Take, for example, the thermocouple, which is a common sensor used for measuring temperature. Thermocouples are 2-wire sensing elements that use the Seebeck effect to measure the temperature at the junction of the two wires. The Seebeck effect creates a small voltage across the junction of two dissimilar metals that correlates to the temperature at the junction. Because of low signal amplitude and low current drive, thermocouple signals are highly susceptible to power-line contamination. For slowly moving temperatures, a low pass filter may satisfactorily reject power-line noise.

Digital filters are preferable for filter characteristics requiring adaptation (such as sharp rejection of a 50 Hz signal versus a 60 Hz signal), sharp cutoff frequencies or stability over time, temperature and production variation. For complex filters, the traditional analog filtering approach requires more components, is subject to drift over temperature and aging, and requires component swap-out for filter characteristic changes.

The thermocouple example can be extrapolated to any other sensor with induced noise that degrades application performance. For sensor applications with higher rates of change, the power-line noise may fall within the spectra of the sensor signal. This may best be filtered using a notch digital filter. Fig. 2 indicates a time-domain representation of a signal buried in noise. Fig. 3 illustrates how the desired signal becomes easily discernable in the frequency domain.

Another illustrative example can be found in a different class of sensor processing; one where sensor accuracy or reliability is desirable, but economically challenging. In such cases, two approaches can be taken. One is to use a lower-cost sensor and augment the lost reliability with digital sensor processing. The other is to combine sensor functions to eliminate a sensor. Alternately, it may be possible to do both. Turbidity detection can be used as a platform to illustrate plausible concepts.

Turbidity sensing

Enlarge this picture Fig. 4. DSCs can optimally handle sensor processing and motor control, and may replace the user-interface MCU, depending on architectural preference.

Turbidity detection can be used to detect the level of particulates in dish or laundry water, to determine that the load is clean enough to terminate a wash cycle early. This helps to avoid additional tub fills, which saves machine energy and time. Industrial-grade turbidimeters, used at water treatment plants to assess water quality in the treatment cycle, are very precise and rugged, but are too expensive for appliance use.

Appliance turbidity sensors employ optical techniques, where a beam of light is passed through the liquid being tested. Two optical detectors — one positioned head-on to the light source, the other at an angle of 90 Deg to the light source — measure the transmitted and scattered light photons, respectively. The greater the concentration of suspended particles in the water, the less light gets through and the more it is scattered. The turbidity of the water is determined by analyzing the ratio of the scattered light signal, divided by the transmitted light signal.

Most dishwashers have removed the detector collecting scattered light information to save cost, which has resulted in reduced sensitivity. On the other hand, while this technique measures occlusion to a degree that is satisfactory for dishwasher applications, it may not be sensitive enough for clothes washer applications where the change in turbidity is relatively small. The frequency-domain analysis of transmitted light would not only provide the strength of the collected signal, but also spectral information that may yield sufficient information to enhance sensitivity for washing machines.

By implementing frequency-domain analysis of turbidity information on a DSC, dishwashers may be able to optimize detergent use and reduce rinse cycles by administering proper concentrations of detergent for local water conditions. Digital sensor processing may also be able to distinguish between particulates, normal turbulence, and the presence of detergent by examining frequency domain characteristics. This may permit the detector to have dual uses: both detergent detection and normal turbidity measurement.

An expensive element of turbidity detection is the material through which the liquid passes. Lower-cost material can succumb to abrasion following long-term exposure to particulates in the water flow. This causes reflected light that reduces the sensitivity of measurement. Digital sensor processing may permit lower-priced materials to be employed, by using digital techniques to improve signal selectivity — thus extending sensor life.

Practical considerations

Enlarge this picture Table 1. Disruptive technology shifts in DC motor control

Appliance engineers do not need to be steeped in DSP technology to take advantage of frequency-domain techniques. Low-cost tools can recommend digital filter types and generate coefficients based on the desired filter parameters. In fact, free, optimized DSP libraries and tools that are available today permit the examination of sensor signals in the frequency domain. DSCs are well-adapted implementation vehicles for this frequency-domain processing, since they have specialized hardware and addressing modes optimized for DSP. Additionally, DSCs incorporate hardware specialized for motor control and power-drive applications, so both sensor processing and motor control can be accomplished with a single chip. Training and vendor support can also accelerate time to market.

The use of DSCs to perform both digital motor control and digital sensor processing presents appliance designers with new opportunities to

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