Capacitive Technologies for Tech-Centric Appliances

Modern homeowners expect their new appliance purchases to be sleeker and smarter than ever before. As a result, leading appliance manufacturers are stepping up with exciting new models with more advanced functionality. With each new model release, appliance manufacturers are incorporating electronic enhancements that appeal to the busy, tech-savvy consumer.

For example, synchronized kitchen appliances are poised to launch a culinary revolution allowing ovens, ranges and microwaves to be set remotely for precision temperature control and mealtime prep.  Appliances can communicate via Bluetooth with smartphones and other networked appliances to coordinate various tasks.  Groceries can be inventoried remotely via built-in refrigerator cameras.  Washing machines and dishwashers can even check if detergent supply levels are running low.  A number of major manufacturers are developing or already marketing lines of connected appliances designed to coordinate and streamline a multitude of household tasks and align with the Internet of Things approach to the smart home.

Appliance motors and other mechanical requirements tend to change at a slower pace than functional performance technology.  Which means that today’s design engineers need to find cost-effective strategies to bring the latest electronics into high-end appliance models for the most demanding consumers, with scaled down options for more economical mid-range and basic models.

Functional and Fun Capacitive Technology

A broadening portfolio of electronics solutions and design strategies already exist to help manufacturers innovate sleek, smart appliances.  Technologies such as advanced capacitive touch sensors provide the design freedom, affordability and scalability to bring enhanced LED lighting and other high-end features into more home appliances.  Next-generation capacitive technologies are empowering greater design freedom and economical ways to incorporate enhanced features that make appliances more functional and appealing for today’s tech-centric homeowners.

Widely deployed and proven in demanding applications, capacitive touch-sensor technology measures changes in capacitance to detect the presence of an object—usually one’s finger on a touch zone identified by an icon.  The feather-light touch required by a capacitive sensor is more comfortable and accessible for all users.  Custom capacitive touch-sensor switches are steadily replacing mechanical switches in newer appliance models because they can provide greater design flexibility and more durable and efficient appliance operation than traditional systems.

Capacitive assemblies can be custom designed and optimized for a full range of appliance applications, from smaller microwaves and beverage dispensers to professional style ovens and refrigerators.  Designed to IP67-rated specifications, capacitive touch switches provide excellent protection against dirt, water and chemical ingress.  Because they are solid-state with no moving parts, capacitive assemblies also deliver longer product life.

An effective integrated capacitive solution generally consists of a graphic overlay, optional backlighting layer and an electrical circuit.  Direct electrical contact is not required for activation, so the overlay panel can be constructed of a thicker durable plastic or acrylic to appear flatter and exude a more desirable glass-like appearance.  Environmental factors are important considerations when selecting and fabricating the overlay.  While most residential homes maintain a relatively stable environment, appliances are affected by daily shifts in temperature and humidity, in addition to frequent use—and occasional misuse by consumer homeowners.

 Empowering Creativity and Scalability

The graphic overlay provides a first impression, but the power behind a capacitive assembly is the circuitry.  Capacitive interfaces are available in multiple substrates, including rigid printed circuit boards or polyester and polyimide flexible circuits, with each presenting unique design challenges, manufacturing costs and operational limitations.  A microprocessor is at the heart of the circuitry to make an appliance operate properly.  The microprocessor allows firmware customization for the functionality, connectivity and improved user experience.

Capacitive touch switches can offer a range of functional and value-added features including custom backlighting, discrete buttons, linear sliders and rotary wheels.  Increasingly, designers are leveraging that power and design flexibility to incorporate energy-efficient low-power LED lighting in creative ways on capacitive touch-sensor switches.  Individual LEDs have a very broad range of performance outputs, input requirements, and environmental specifications, which underscores the need for a customized solution for an entire assembly design.  For example, a basic dishwasher might feature simple on-off lighting for all keys, while a high-end model might feature the same basic overlay incorporating multi-color LEDs and added functionality for adjustable controls or gradual dimming.  This level of design scalability typically translates into cost savings for the manufacturer.

In one recent prototype project, an electronics solutions manufacturer developed touch-sensing switch panels to coordinate the look and feel of a refrigerator and dishwasher that a customer was designing for the same product line.  In addition to aesthetically matching, they wanted to be able to repurpose the same basic touch-sensor schematic for different appliances and different models.  The manufacturer was able to help standardize the overall user interface for optimal impact, functionality and compatibility with the customer’s existing and future appliance products.  The scalable prototype assemblies were both relatively long and narrow, with an integrated microcontroller for panel functionality.  The detailed keypads featured numerous tightly spaced capacitive buttons, slides and rotary finger controls that could be individually or collectively lighted—and gradually dimmed.

Designed as a thin layer between the overlay and electronic circuitry, LED backlighting generally offers a cleaner aesthetic on appliances than side-lighting techniques or rimmed buttons.  While an LED provides a single point of light, microscopic texture causes that light to be spread uniformly over a backlit area.  Both prototype designs incorporated molded light guides with diffused LED backlighting for more uniform lighting coverage over a larger surface area of the visible overlay.  High-speed serial communication techniques are used to manage lighting control and sensor reports to ensure consistent responsiveness.

Eye-Catching, Highly Efficient and Robust

Quality features and sleek design create a first impression for appliance shoppers.  Growth of capacitive touch inputs is now outpacing mechanical interfaces and resistive touch controls in home appliance designs.  A scalable and enabling technology, capacitive switches provide overall higher reliability and more eye-catching LED enhancements in intuitive user interfaces.  Custom capacitive designs can incorporate and blend multiple switch formats and layouts, and combinations of tactile and non-tactile products.  Other key advantages in next-generation appliance design include:

  • Robust and durable solid-state design with no moving parts to wear out
  • Seamless overlays for easy appliance cleaning, resistant to contaminants and chemicals
  • Feather-light actuation through the protection of thick polymer overlays or glass
  • Elegant designs with virtually unlimited cosmetic options—colors, texture and unique LED backlighting solutions
  • Streamlined integration with functional control units and customized firmware

Consumers trust leading brand appliances and count on the reputation and quality of high-end productsCapacitive switch technologies can help a manufacturer build and differentiate their appliance models on the showroom floor to capture the attention of tech-savvy buyers.

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