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issue: November 2005 APPLIANCE Magazine European Edition

Sensors and MCUs
Integration, Interconnection, Differentiation

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David Simpson, Contributing Editor

Microcontrollers and sensors are helping to increase the pace of product introductions, making it easier to quickly engineer appliances with unique feature sets.

SmartFan Inversion is a fan speed control that combines an a.c. to d.c. power supply and d.c. fan control/alarm to provide the best of both worlds. The device, from Control Resources, Inc. (Littleton, MA, U.S.), is said to offer benefits such as acoustical noise reduction, temperature regulation, greater product reliability, and improved safety and energy savings.

Electronics capabilities are improving and costs are declining. That helps appliance companies come up with new sets of product features and capabilities. That, in turn, fuels the accelerating pace of product lifecycle. Appliance designs turn around still more quickly, challenging engineers to run ever-faster.

The inherent flexibility of electronics can help the appliance engineer by making it easier to combine multiple functions. As an example, Tom Ricono, vice president of business development at Diehl Controls North America (Naperville, Illinois, U.S.), points to laundry appliances. “With the horizontal platform, we are able to integrate electronics in both machine and motor control to greatly improve efficiencies, clean-ability, and perform many product enhancements,” he says. “Advancements and price reductions for semiconductors allow appliances to be smarter, use more sensors in real-time, and offer more control to the user. Faster microprocessors allow real-time embedded systems to perform instantaneously.”

Ricono says one example is controlling motor speeds to re-balance spin loads as the imbalance happens and before it becomes a nuisance to the user. Almost unlimited code space allows multiple languages, friendly one-touch starts and icons that mimic computers. “With increased inputs and outputs, large code routines and multiple calculations, being able to run at real time and react instantaneously gives the appliance better performance and can save energy.”

With product life cycles being reduced every decade, the development cycle must also be reduced while software size and complexity is increasing. “In the 1980s, average code size was 1 to 4K, then in the 90s it was 8 to 32K. Now programs are exceeding 128K, and full alphanumeric displays are common,” Ricono notes. “One issue is verification time. Probably every eight lines of code is a decision, so with 128K of code, there are thousands of decisions. Does increasing code sizes and, therefore, complexity mean more test time? Nobody wants to have the software mess of Microsoft, with patches and errors and hidden bugs surfacing after release.”

To address the issue, Diehl Controls uses an Object Oriented Process said to greatly reduce software development time, reduce verification time, check all decision paths, and improve reliability. “This allows us to deliver error free code and reduce the approval stage without putting our customers at risk,” Ricono says.

Another trend has been the move toward more sophisticated electronic controls. In the 1990s, OEMs began to increase features and complexity with the use of 4-bit microcontrollers (MCUs). By the mid- to late-90s, appliance companies began to look to 8-bit controllers to handle more complexity. Some appliance makers chose to use low-cost 16-bit controllers to save money by providing extensive peripheral functions, which can eliminate the need for external devices and facilitate the system integration process without cost penalty.

Selco/ECC (Anaheim, California, U.S.) suggests that appliance manufacturers can cost-effectively provide improved temperature precision by replacing traditional bulb and capillary temperature thermostats with electronic temperature sensing and control. Typical applications include cooking equipment, refrigerated and frozen food storage, chillers, and HVAC equipment. Available in three configurations, the controllers provide a differential of +2ºF (-16.7°C) high accuracy thermistor temperature sensing of 2ºF, and a set point adjustment of 1ºF (-17.2°C) resolution, set by a potentiometer.

Faster Boiling

Sensor technology is also bringing appliance makers performance benefits. Sensors for glass ceramic cooktops, for example, need to work in an extremely high-temperature environment—in some cases up to 800ºC, reports Kim Lezatte, vice president of sales at Ceramaspeed Inc. (Maryville, Tennessee, U.S.). “We’ve been using a single primary high limit switch to assure that temperature limits are not exceeded. But these have a fairly wide tolerance—about 25ºC to 30ºC. Because of the tolerance, we can’t take the maximum temperature quite as high as we would if we used a sensor with a narrower tolerance. In addition, the control turns the heating cycle on and off to assure it doesn’t overshoot the maximum top glass temperature of around 560ºC. This slows the amount of time it takes for water to boil on the glass ceramic surface.”

By switching to a more accurate high temperature sensor and changing how the control operates, Ceramaspeed says it reduces boil time as much as 19 percent. The new platinum sensor has a tolerance of just 7ºC, allowing higher set points. The EPIC control, from DDS Electtronica of Modeno, Italy, actually aims to take the temperature higher than 600C for up to 7 minutes for more rapid boiling. After that, the temperature automatically drops to between 590ºC to 600ºC. Due to the risk of the high heat damaging the surrounding cabinets, after another 20 minutes, the temperature will again drop, this time to about 560C.

The ZCPR Series of potential relays is a recent entry in a line of products for the HVAC/R industry. Manufactured by Zettler Controls, Inc. (Aliso Viejo, California, U.S.), the relays are used to assist in the initial function of single-phase motors that employ start capacitors for high torque. The coil of a potential relay is energized by the potential of the start winding. When this voltage increases to the pick up value, the contacts will open and disconnect the start capacitor. The relay will remain energized until the start winding voltage is removed, or when it decreases below the dropout value.

"Zensing” a Connection

Interconnecting appliances has long been practical, with signals carried wirelessly or through specialized cables, phone lines or power lines. Wireless technology is a promising approach, dispensing with the expense of dedicated hard wiring and compromises in performance caused by dual-purpose wiring.

Wireless technology, used in products like cordless phones and television and audio remote controls, is growing. Wi-Fi and Bluetooth technologies are also playing a growing role in today’s computers and peripherals, cell phones, and audio/video equipment.

Despite consumer interest in networked wireless features, many OEMs are concerned about expense, reliability, complexity, eventual obsolescence, and a lack of widely acceptable standards. The good news is that chip and sensor and control suppliers are making efforts to come up with wireless solutions that are relatively low cost, reliable, widely accepted, and having the ability to communicate between different manufacturers’ products. One development is the Institute of Electrical and Electronics Engineers (IEEE) 802.15.4 ZigBee standard.

“Some wireless solutions in the home, such as cell phones and WiFi, offer high bandwidth, which allows them to push through a lot of data, including voice and video,” says Stephen Caldwell, director of the Home Appliance Solutions Group at Microchip Technology Inc. (Chandler, Arizona, U.S.). “But because of the high bandwidth, there is a lot of overhead, and the expense is higher. Other technology, such as Bluetooth, offers less bandwidth and somewhat lower expense. But for many applications, you really don’t need even that much bandwidth. If you are simply turning things on and off or setting temperatures, for instance, your technology doesn’t need voice or video capabilities. It is in these simpler command and control applications that the IEEE 802.15.4 ZigBee standard can shine.”

To promote and technically advance the standard, several companies have joined to form the ZigBee Alliance. More than 100 members participate, including Microchip, Freescale Semiconductors, Mitsubishi Electric Corporation, Philips Semicond-uctors, Honeywell, and Samsung Electronics Company Ltd. Last December, the group ratified the first ZigBee specification after 2 years of worldwide development and interoperability testing.

One of the key advantages of ZigBee, says Caldwell, is the interoperability. “If one vendor has the technology, its products will be able to talk to another vendor’s,” he points out. “ZigBee networking can support many topographies, such as star or mesh, and can be used to connect thousands of objects—certainly more than are likely to be needed within a house. Another advantage is low-power operation, which can result in battery life measured in years.”

Brett Black, commercial wireless operations manager at Freescale Semiconductor, Radio Products Division (Tempe, Arizona, U.S.), is seeing a push from customers toward standards-based solutions. “In the last decade I’ve never seen a product that has such customer pull and interest. There are few customers who haven’t heard of ZigBee or aren’t interested in wireless connectivity in their markets,” he tells APPLIANCE.

Black adds that Freescale will offer fully compliant ZigBee chips once specifications are published. “And, as you see more compliant platforms in the market, you will see more customers adopt the standard,” he says. “Another inducement is that the cost of licensing a ZigBee compliant solution could be as little as U.S. $3,500.”

This customized regulator for SR motors comes from Matsushita Electronic Components (Europe) GmbH (Lüneburg, Germany). The entire control is based on an 8-bit microcontroller that provides comprehensive functions at comparatively low manufacturing costs.

Riding the Z-Wave

While ZigBee offers promise, it is not the only technology in town. Z-Wave was developed by Zensys Inc. (Copenhagen, Denmark), which initially included the technology in temperature and light controls that it produced. In 2001, the company decided to drop the controls and focus on its core technology. It began shipping its own chip and software stack to other home products companies to implement.

“At this stage, we have some 125 companies that have enabled the technology in such products as light dimmers and switches, remote controls, thermostats, motion sensors, security systems, and garage doors,” says Raoul Wijgergangs, vice president of business development at Zensys. “There are currently about 50 products on the market, and we anticipate 250 will be shipped by the end of the year.” Among companies in the Z-Wave Alliance, which promotes the technology, are Leviton, Wayne Dalton, Danfoss, and Intermatic.

The ZW0102 Z-Wave single chip is a mixed signal chip integrating RF transceiver, Z-Wave protocol storage and handling, and OEM product application storage and handling in one chip. An on-chip 8-bit MCU handles both the OEM application as well as the wireless communication protocol. Free on-chip flash memory gives the OEM the opportunity to download and run most control applications directly on the chip. This eliminates the need for an additional microcontroller and external flash memory for application code storage.

One proponent of Z-Wave is Intermatic Corporation (Spring Grove, Illinois, U.S.). It currently has six lighting controls and hand-held remotes using the technology. “Our goal is to have 60 SKUs in the next 12 to 18 months,” says Jeff Bovee, marketing manager for Home Controls. “These will include moisture sensors, door/window sensors, motion sensors, temperature sensors, and others for both the industrial and retail markets.” According to Bovee, Intermatic chose Z-Wave because it is reliable and is available at a fairly low implementation cost for a lot of applications.

Getting the Lead Out

Many electrical component suppliers are affected by RoHS, technically the 2002/95/EC Directive of the European Parliament and Council. RoHS stands for Restriction of the use of certain Hazardous Substances in electrical and electronic equipment. The aim of the directive is to ban heavy metals (such as lead, mercury, cadmium, and hexavalent chromium) and two brominated compounds (PBB and PBDE). The directive will be applicable throughout the European Union by July 1, 2006.

Appliance suppliers have been working to comply, where applicable. Martin Leslie, market manager of Therm-O-Disc (Mansfield, Ohio, U.S.), points out that the latest proposed RoHS standards allow the use of cadmium in his company’s contacts. “As a result, the RoHS initiative has little effect on our products,” he says.

ST Microelectronics (Tours, France) reports that in 2000, it launched a strategic program named Ecopack to develop and implement solutions leading to environment-friendly packaging and to progressively ban lead and other heavy metals from its semiconductor manufacturing lines. The company has selected three technologies to match the different technical and quality requirements and cover the full spectrum of packages:

• NiPdAu technology is well known on the market and is sometimes referred to as PPF (Pre-Plated Frame).

• Pure tin (Sn) is also a common lead-
free solution used by semiconductor manufacturers.

• SnAgCu ball is the material chosen for the balls of all “Ball Grid Arrays” and balls and bumps of Flip-Chips (currently using PbSn).

The Next Generation

Another area that continues to develop is capacitive sensor technology. Quantum Research Group (Southampton, United Kingdom) earlier this year introduced the QWheel Rotary touch chip, which has a proximity feature that detects a hand moving near the sense field even 50 mm away from the panel surface. This can be used to “wake up” the product and can work in a very low power mode while still sensing hand proximity.
“Menus and options are available now on a huge variety of electrical equipment from washing machines to telephones, and one of the most important factors associated with this is the ease of use, manipulation, and input,” offers George East, product line manager for Quantum’s Exotic Products Division. “Hence, the popularity of this rotary input device. The rotary allows the user to trace their fingers around a ring that will then scroll up and down through their menu. A further advantage of this product is the ability to have a separate proximity detect function which enables the sensor to recognize a hand approaching.”

As well as being a scrolling device for a menu driven piece of equipment, East says the technology can also take the place of a traditional potentiometer, with the added advantages of not requiring a hole in the panel for a post and then a separate encoder board to take the signals from the pot. “It is for these reasons that we have had inquiries for appliance producers to replace traditional knobs and dials that have always been bulky, unsightly, and difficult to clean around,” he tells APPLIANCE.

It is clear that today’s popular premium appliances require sophisticated sensors to achieve the enhanced performance expected. “The user of a high-end appliance demands a quiet, energy-efficient machine that delivers uncompromising results. The sensors and microcontrollers needed to achieve flexibility, high accuracy, or low power have different requirements and need different technologies,” notes Caldwell of Microchip. “But, as time progresses, the technology utilized for high-end appliances will be optimized for cost and used in standard appliances. Thus, the technology that can be mass produced at a reasonable cost will prevail.”


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