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issue: May 2009 APPLIANCE Magazine

Sensors and Microcontrollers
Learning New Tricks

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an APPLIANCE Staff Feature

Sophisticated microcontroller (MCU) solutions are helping appliance engineers meet prepare for new energy efficiency strategies.

OEMs are turning to suppliers for solutions to increasingly complex, urgent energy-efficiency issues—and notably to suppliers of microcontrollers (MCUs). Sophisticated sensing and the right kind of multifunctional control capability allow appliances to be fined-tuned, to whittle down raw-energy usage. Just as importantly, it enables appliances to learn the new energy tricks that will make these devices part of the global energy-efficiency solution.

On the Grid

Electrical power grids are getting smarter and electric utilities will increasingly be networking with, and controlling, home appliances. Smart Grids will allow utility companies to connect to home equipment and manage appliance operation in ways that maximize energy usage and tame power demand spikes. The promise to customers, in return for handing a degree of control of their home appliances to the utility companies, is significant energy-cost savings.

These savings have already been demonstrated in pilot projects by Italy’s Enel S.p.A. electrical utility as well as utilities in Austin, TX, U.S., and Boulder, CO, U.S. Now, efforts in the United States to bring Smart Grids into being are accelerating. The National Institute of Standards and Technology (NIST) is scheduled to make its Interim SmartGrid Roadmap available in June 2009 and a Roadmap version 1.0 in September 2009.

Engineering appliances for networked control and remote monitoring is no simple task. For now, Texas Instruments (TI; Dallas, TX, U.S.; www.ti.com) is starting with a portfolio of utility metering devices. Meters, home thermostats, and large appliances communicate to help consumers make informed choices about electricity. Among the TI offerings is a new system-on-chip MCU solution designed to make electricity metering (e-metering) applications more cost-effective. It is designed to cut electronic bill of materials (EBOM) to the $1 range in high volumes for single-phase e-metering applications. The MSP430FE42x2 MCUs integrate metering functionality onto a single chip and offer ultralow power operation, so that only simple voltage regulation is required for a complete solution. FE42x2 MCUs come in a 64-pin LQFP package, offering up to 32 kB of in-system programmable flash memory.

A unique embedded signal processor (ESP) peripheral fully automates energy conversion by integrating two independent, high-resolution sigma-delta ADCs, programmable gain amplifiers, a temperature sensor, precision voltage reference, H/W multiplier, and a dedicated fixed-function MSP430 CPU. A second, fully programmable on-chip MSP430 CPU is available for application processing and communication functions. An enhanced watchdog timer, brownout protection, and a supply voltage supervisor increase system reliability. A 128-segment LCD driver, a three-channel 16-bit pulse-width modulation timer, serial communication port, and a basic timer for a real-time clock function provide all functionality for a complete meter implementation while saving board space, reducing development time, and streamlining time to market. The device operates from a 3-V supply with the CPU and ESP active at only 2.5 mA. During a power outage, the device can operate in standby mode at 1.1 µA with real-time clock function active. Ultralow power can enable 10- and 20-year battery life in metering applications.

Putting Appliances to Rest

Another primary theme of energy reduction efforts has to do with standby power—the power used by devices when they’re not actively performing their function.

Microchip Technology Inc. (Chandler, AZ, U.S.; www.microchip.com), addressed that problem in recent weeks with the launch of its next-generation low-power PIC MCU families with nanoWatt XLP eXtreme low-power technology. The controllers offers sleep currents as low as 20 nA. The new 8- and 16-bit nanoWatt XLP portfolio provides designers with a compatible low-power migration path. It still offers on-chip peripherals for USB and mTouch sensing solutions. The combination of functional capabilities and low-power is designed to meet growing needs for battery-powered or power-constrained applications.

The new MCU families “have surpassed the competition by a substantial margin to offer a new industry benchmark for the lowest sleep-current consumption,” said Tony Massimini, chief of technology at Semico Research Corp. (www.semico.com). “When you factor in the integration of EEPROM, oscillators, USB, and capacitive touch sensing peripherals, the potential reduction in system-level power consumption is quite substantial.”

In addition to sleep currents down to 20 nA, the MCUs offer real-time clock currents down to 500 nA and watchdog timer currents down to 400 nA. Most low-power applications need one or more of these features. By offering all three at such low levels, the MCUs provide the designer with the flexibility to engineer appliances that make use of any or all of these features, take advantage of sealed battery design, or even integrate energy harvesting. The design could simply enable extended battery life; in some designs, the MCUs could enable applications that run for 20 years on a single battery.

Design Tools

MCU suppliers have another challenge on their hands: giving OEM engineers and designers the confidence to design with components that are, by their nature, highly complex and diverse in their capabilities. The challenge for OEM engineers can be exacerbated as the economy creates leaner engineering teams. Suppliers are eager to provide tools that make design and specification easier.

MCU supplier STMicroelectronics (Geneva; www.st.com) created the STM32 Primer2 to allow product designers to prove design concepts quickly and independently. The device looks something like a mobile phone, with a 128 × 160-pixel touch screen, a joystick, and an extension connector, and it comes loaded with sample applications. It has a built-in USB port, a MicroSD card slot, an accelerometer, an infrared transmitter/receiver, and other capabilities that let the user quickly add capabilities to applications. The components are managed through the open-source CircleOS software.

The embedded development device allows users to quickly turn a concept into an attractive-looking demonstrator, which the supplier says is becoming important as product innovators increasingly vie for independent funding. The unit is intended to allow for the creation of a high-quality prototype, rather than a conventional engineering development board, to create a better first impression with little investment.

As design engineers try to get a handle on an increasingly complex regulatory landscape, they’ll need all the help MCU suppliers can offer to facilitate the development of highly efficient next-generation appliances.


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