issue: February 2007 APPLIANCE Magazine
Switches and Switching Devices
Touch Chips Yield Prize-Winning Appliances at Gorenje
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appliance maker Gorenje made a conscious decision to move upmarket, and
over the past 5 years it has worked to strengthen its image as a design
and technology trendsetter.
Gorenje’s cooktop slider controls allow “direct access” temperature setting without the need for slew keys, which is said to create a highly desirable replacement for mechanical knobs.
A milestone of this effort was the launch of its Pininfarina series of kitchen appliances in 2005. In November 2006, this series received the prestigious Manufacturer’s Award from The Designer magazine—the third prize won by this product line after little more than 1 year in the market.
Key to this award-winning design is the use of touch controls from Quantum Research Group in Southampton, England. In a first-ever product design, Gorenje made use of Quantum’s QT401 QSlide sensing chip for three of its Pininfarina cooktop controls, along with Quantum QT1100A ten-key chips for discrete buttons. These spread-spectrum charge-transfer devices allowed Gorenje to develop user interfaces in a fresh way.
There were problems with the former switches, according to Hal Philipp, CEO of touch chip provider Quantum. “Mechanical switches were not consumer appealing or functional enough to do the job,” he says. “The product definition called for touch controls to enhance the product and make the product more upscale. Mechanical switches are not reliable enough, nor are they differentiating enough.”
The new chip is used in Pininfarina cooktops as a temperature setting mechanism, allowing “direct access” to the desired heat setting rather than the more traditional “slew” type control, which most users find tedious. The chip is a charge-transfer based capacitive sensor IC that detects finger position along a strip. The sensor’s fields can penetrate up to 5-mm thick glass panels.
Gorenje’s Pininfarina kitchen makes extensive use of touch controls to give it a sleek, stylish look with easy to use, intuitive user interfaces.
The basis of this technology is the use of CMOS switches to charge the
sensing electrode strip to a voltage, then transfer the electrode
strip’s charge to a pair of fixed capacitors whose voltages are then
measured. This 14-pin surface-mount device has a resolution of 127
positions across the sensing strip. The strip can be a resistive film
or resistor ladder, or interleaved copper PCB electrodes. It uses
spread spectrum burst modulation to suppress the effects of electrical
noise. The interface is SPI, and the part operates over a 2.7 V to 5 V
range. The chips include automatic drift compensation and automatic
Up to 10 additional touch buttons come from the QT1100A 10-key chip
that senses touch or proximity using capacitive charge-transfer
technology. The basis of this technology is the use of CMOS switches to
charge the sensing electrode to a voltage, then transfer the
electrode’s charge to a fixed capacitor, whose voltage is then
measured. This 48-pin surface-mount device also features patented
Adjacent Key Suppression™ (AKS), used to resolve touch ambiguity when
more than one key is touched unintentionally, such as in tightly spaced
This device uses spread spectrum burst modulation to suppress the
effects of electrical noise on performance, and offers three output
interfaces: UART, SPI and scanport. It operates over a 3.3- to 5-V
range. The 10-key chip includes automatic drift compensation and
Both chips project a touch sense field through thick glass, including glass cooktops.
“Gorenje’s choice of touch slider and button chips for its
Pininfarina series allowed them to create distinctive, high value
designs not found elsewhere. Gorenje’s choice of controls was inspired,
not only because it won them so many immediate design awards but also
because it allows intuitive non-mechanical user controls, easy
wipe-down functionality, electrical robustness and importantly a high
degree of design flexibility simply not available with other control
technologies,” Philipp says.
According to Joze Dermol, lead engineer of Gorenje’s R&D
department, “The positive experiences customers report about these
touch controls made us think, research and develop user interfaces in a
different, fresh way. With these devices, we see that there are no
longer problems for us to create any kind or shape of appliance front
panel, solving a major design barrier. We realize now that
touch-sensor-based user interfaces can meet any design demand, and the
resulting modern design and user-friendly interface no longer needs to
be an exclusive feature.”
Philipp says Quantum is working with Gorenje on next-generation user interfaces for kitchen appliances.
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