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issue: December 2009 APPLIANCE Magazine

Control Panels and Displays
Smart Interface

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by Yaling Lee, managing editor

Appliance engineers are using sophisticated tools to design control panels in less time, even while enhancing functionality and durability.

Whirlpool’s Latitude refrigerator marks the firm’s first use of a color touch LCD screen in refrigeration. The resistive LCD screen allows users to set the exact amount of water they want dispensed.

The consumer electronics world is excited about the potential applications of recently introduced multi-touch technologies for touch screen control panels and the roll-out of 3-D TV. Hype about display advances hasn’t gone unnoticed in industries outside CE.

“The appliance industry continues to watch the consumer electronics industry for trends. Once a new technology is tested in the market, the appliance industry will definitely look at adding it to their products,” says Stacey Gearhart, senior category manager, refrigeration, Whirlpool. This is evident in the adoption of touch screens, which Gearhart sees as more and more popular in appliances.

Can the same be said for the multi-touch control panel? Kelly Devin, marketing manager for appliance markets, 3M Touch Systems (Austin, TX, U.S.; www.3m.com), thinks it is just a matter of time. “Consumers used to a multi-touch interface will eventually drive the need for this interface in home appliances.” But it will be slow in coming. “Manufacturers are exploring the possibilities, but since the technology and capability are fairly new, it may take some time to permeate the appliance market.”

Resistive touch screens remain a common choice for touch sensitive solutions, but Devin sees OEMs turning to glass-based solutions in applications requiring better durability and screen readability. The MicroTouch System SCT3250CX, introduced earlier this year, is a surface-capacitive system designed as a cost-competitive alternative to five-wire resistive touch screens. It is said to provide better surface durability, faster touch response, and 11.5% higher optical transmission than average five-wire resistive systems. For high-end, large-display applications, Devin says appliance makers can consider 3M’s new projected capacitive multi-touch screen, which tracks up to 10 fingers or multiple users, with less than 15 milliseconds of response time.

The 3M MicroTouch System SCT3250CX, available in display sizes ranging from 6.4 to 12.1 in. and based on 3M Surface Capacitive touch technology, offers a cost-competitive solution to five-wire resistive touchscreens with the added value of a durable touch surface, premium optical characteristics, and fast, reliable touch response.

Simplified Solutions

Much of the advancement in displays is focused on thin films that enhance screen durability or performance. Opcuity Fingerprint Resistant (FPR) films from UniPixel (The Woodlands, TX, U.S.; www.unipixel.com) provide a micro-structured surface with features less than 10 µm high. According to Jim Tassone, UniPixel’s CFO, a fingerprint or oil smudge (typically 3–4 µm high) is visible on a flat surface as an added structure due to differences in refractive index, contrast, or light reflection relative to the underlying material. “A structured surface hides fingerprints by allowing the fingerprint or oil material to wick into the valleys between the structures and not be detected due to a surface differential.” The Opcuity films also add a unique feel that can enhance tactile feedback.

Many suppliers offer comprehensive packages that simplify interface design. Bijer Electronic (Malmö, Sweden; www.beijerelectronics.com) and its subsidiary Hitech Electronics Corp. developed Programming-Free Display (PFD) platforms, which make it “effortless for users to upgrade their products from text-based or monochrome display to color graphic display,” says Edison Yang, product manager of Hitech. On the software side, the PFD-Designer eliminates the need for LCD interface programming. Aided by a simple drag-and-drop system and a large predefined object library, engineers can edit graphic objects and set touch-screen positions at the same time. On the hardware side, the firm offers an off-the-shelf resistive TFT LCD touch panel that contains all the components required, so companies don’t need to stock any panel parts. Yang adds, “By using dual port RAM technology, MCUs read and write memory via PFD just like SRAM. There is no need to debug on the PFD end.”

Synaptics (Santa Clara, CA, U.S.; www.synaptics.com) helps manufacturers transition from resistive screen to projected capacitive touch applications. It recently launched the single-touch ClearPad 1000, competitively priced for the mass market and featuring zero borders, high optical clarity and noise immunity, and low power consumption. Binay Bajaj, ASIC strategic marketing manager, tells APPLIANCE, “Other companies may only offer the chip or part of the full solution, putting the burden of integration on the OEM.” Synaptics’ Solution Stack is designed to help bring the OEM from design to production of a capacitive sensor user interface, with support for systems engineering, software design, and gesture recognition, to human factors and testing and qualification. The digital microcontroller and analog mixed-signal hardware was designed from the ground up for touch applications. “What that means is that no cycles of the controller are wasted and, in general, the technology can run at much lower frequency to provide the same or better functionality than you would find in a generic microcontroller,” explains Bajaj.

Touch Panels on Steel and Stone

Touch-sensitive functionality isn’t limited to plastic or glass panels, as ITW ActiveTouch (Buffalo Grove, IL, U.S.; www.itwactivetouch.com) proves with its trapped acoustic resonance technology. The switches can be made of any material capable of supporting shear and torsional mechanical waves at ultrasonic frequencies, including metal, ceramic, and stones. In stainless steel it provides several advantages. “The seamless stainless interface leaves no crevices for bacteria to build up and is easy for the user to clean,” says Charles Igwekala, sales engineer, security, generators, and appliances. Since the stainless steel is already purchased as part of the product, all that needs to be done is make the passive component active. “The mechanical assembly requires the bonding of transducers to the touch area. Manufacturing advancements have optimized this process,” Igwekala explains. “Once the mechanical assembly is complete, the balance of the assembly is handled in electronics, which can be consolidated into the main control.”

From Analog to Digital/Networkable

Appliances are upgrading to new technologies to keep up with the need for networking. “One trend we have seen recently is an increasing number of appliance OEMs moving to replace their old analog controls with fully-digital, networkable control units,” observes Chris Domanski, project manager at Renau Electronic Laboratories (Chatsworth, CA, U.S.; www.renau.com). Domanski says, as opposed to analog controls, the latest digital controls are compact, offer many programmable functions, and can network with other digital devices to further expand an appliance’s functionality.

ActiveMetal switches are solid-state devices with no moving parts to wear out, so the number of activation cycles is almost unlimited. They are water-, dust-, and vibration-proof.

Designed for the foodservice industry, Renau’s UCM-737 Universal Control Module interfaces with the firm’s Single Wire Communication network, which offers scalability and upgradability while eliminating the need for expensive and complicated wiring harnesses. The display device features a 16 × 2-in. LCD, an intuitive interface, five quick recipe buttons, and an onboard buzzer. Operating at temperatures from 32°–176°F, the control module is fully encapsulated for protection from humidity and shock. “With simple, easily understandable interfaces, it becomes much easier to train operators to use these appliances,” says Domanski. “This results in reduced training costs, less time using the interface itself, and less waste caused by user-error because the functions, programs, recipes, and all of the other features an appliance offers are stored in the controller hidden inside the appliance.”

Renau’s UCM-737 Universal Control Module

With the strong push from the Obama administration for the development of Smart Grid, the market for smart appliances is bound to grow, and so will integrated control solutions for those appliances. As Warwick Stirling, global director of energy and sustainability for Whirlpool Corp., puts it, “It’s at this consumer touch point where we will likely see the advancement of a range of applications for various consumer conveniences as secondary technologies to the core Smart Grid connectivity environment.”

Expanded Coverage

High-Resolution Finger Sensing
LCD Displays Withstand Extreme Temperatures
Touch-Sensing Controller Performs Automatic Calibrations



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