Small Sensors Make a Big Difference in Consumer Products

Forecast to have an increasing impact on solid-state sensor applications (according to IC Insights' O-S-D Report), consumer electronics add a new twist to sensor manufacturers' and system designers' plans. While consumer electronics products have many different requirements and constraints from other markets, the added use of sensors will benefit not only the products that incorporate them but other applications, as well. Market segments that can benefit include those that can take advantage of the unique aspects of the consumer electronics market such as reduced time-to-market and reduced time-to-volume, as well as the physical attributes of consumer electronics' sensing products, including the requirements for small size, low power consumption and more. Motion is a growing sensor opportunity but many other sensor technologies are finding their way into consumer electronics products.

Motion Makes Sense

In the exploding consumer market for solid-state sensors, motion sensing has changed the way users interact with products and also enabled entirely new products. Adding a single-, dual- or three-axis accelerometer provides the ability to sense motion. From simply detecting a free-fall to lock a hard disk drive and prevent damage, to sensing complex motion in games from golf to bowling, small microelectromechanical systems (MEMS)-based accelerometers have had a big impact on consumer products.

With the first sound effects system where guitarists could control Wah and Phaser/Flanger effects using hand and body motions, Source Audio's Hot Hand redefined the way guitarists personalize their performance.

More recently, the company's Soundblox guitar effects pedals liberated guitarists from a fixed position and provided them more dynamic sound capabilities. Analog Devices' ADXL3xx family of multi-axis accelerometers provides the motion sensing for Hot Hand but these newer consumer applications have not happened overnight. ADI's initial accelerometers were developed for sensing in automotive air bags.

“Thanks to nearly two decades of manufacturing experience that has helped ADI dramatically reduce the size, cost and power consumption of MEMS devices, motion sensing technology today is giving designers options they never had before,” says Harvey Weinberg, applications engineer, Micromachined Products Div., Analog Devices Inc.

ADI's ADXL3xx family of multi axis, low-g iMEMS® motion sensors were developed for consumer product applications. The ADXL330, a monolithic three-axis accelerometer with signal conditioned voltage outputs, senses acceleration with a minimum full-scale range of ±3g. The three-axis accelerometer can measure the static acceleration of gravity in tilt-sensing applications, as well as dynamic acceleration resulting from motion, shock or vibration.

“Design cycles for consumer products can be months or years depending on the product and competitive environment. In contrast to the auto industry, however, they go to market right away,” says Weinberg. “Product life cycles are measured in months and not years.” With the new consumer accelerometers, other markets can take advantage of the new performance capability sooner than if automotive was driving the development.

More than guitar players are excited about the new functionality from motion sensing. Apple popularized the display screen that knows its place (orientation) in the iPhone. The highly integrated phone uses STMicroelectronics' LIS302ALB three-axis linear accelerometer. Operating from a 3.3V supply, the ±2g accelerometer provides an analog output. Similar to other MEMS accelerometers, the LIS302ALB has potential applications in appliances and robotics.

A Touch of Class

In addition to providing a flexible, reliable and cost-effective user interface, touch-sensitive controls are sealed from spills and dust and have no moving parts to wear out. With these controls, engineers can design touch-based rotary wheel and linear slider interfaces with the ability to hide or illuminate buttons and “morph” touchpad patterns in cell phones, portable media players, remote controls and more. However, home appliance and industrial control equipment can also take advantage of the technology.

Products like Freescale Semiconductor’s MPR083, a capacitive eight-position rotary touch sensor controller and MPR084, a capacitive eight-pad touch sensor controller simplify the design process.

“These parts were developed specifically for consumer applications but based on one developed initially for automotive,” says Bryce Osoinach, systems and applications engineer, Freescale Semiconductor. Freescale’s initial products were automotive-qualified electric-field products. Recently, the company announced its first microcontroller (MCU)-based state machine products for the consumer market.

“Automotive applications such as occupant detection that utilize Freescale’s automotive qualified electric-field products can take several years to go into production. However, consumer sensor applications can be as short as three to six months,” says Darrell Simms, senior product marketing manager, Freescale Semiconductor.

An Open-Shut Case for Sensors

A folding type cell phone case enables a larger display but something has to alert the phone when the case is opened or closed. Instead of a mechanical switch that would be subject to wear out, many cell phone makers are opting for a Hall Effect sensor to indicate an open or closed position. For this application, ROHM's BU52000 series provides a compact and thin-profile package with a mounting area of only 1.1 x 1.1 x 0.5 mm. Besides improved reliability, the non-contact sensing technique also provides increased design flexibility. The tiny Hall Effect device can open possibilities in other markets.

How Hot is It?

Automotive still provides a driving force for new sensing technology that subsequently gets modified for consumer and other applications. For example, expanding on its automotive-proven family of intelligent infrared, non-contact thermometers, Melexis recently introduced the MLX90614xAC with a narrow Field of View (FOV). A silicon chip with a thin, micromachined membrane sensitive to the infrared radiation of a distant object provides the sensing element. In the same package, a custom signal conditioning chip amplifies and digitizes the signal and calculates the object's temperature. With a Field of View of only 35 degrees without the use of costly infrared optics, the infrared thermometer may enable new applications in microwave ovens, true non-contact fever temperature measurement and industrial temperature control.