Interface Designs Benefit from Specialist Support

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To provide customers with a choice of MMIs, Capital Cooking offers some models of ranges with a membrane switch panel composed of deformable switches that make contact with the control system. Some of the oven products feature a passive touch-capacitive glass panel that communicates with the control system via software.
Photo courtesy of Capital Cooking Equipment/Jayco mmi.

The design of an HMI or MMI is rapidly growing in its complexity but can be simplified by consulting an interface specialist-before proceeding with design work

Ed Sullivan

Interface design is increasingly impacting the success or failure of electronic products, but a well-designed interface is no easy thing to get right. Given the complexities involved in interface design, it is no wonder that today’s product designers and engineers are turning to interface specialists to support the design of their products.

Whether HMI (human-machine interface) or MMI (man-machine interface), these specialists are experts in dealing with the highest levels of interface complexity, both human and technological.

“There are instances when it is important to work with an interface specialist that has the full capability of supporting you from the ground up,” advises Joey Kitabayashi, vice president of engineering at Capital Cooking Equipment (Santa Fe Springs, California). Kitabayashi adds that the type of control panel can add to the need for a specialist supplier; for example, glass touch-capacitive and other panels that require software, which is an additional interface.

The design of the HMI or MMI has made a vital contribution to the success of countless products across the spectrum of industries ranging from the most sought-after consumer products to most business, medical and industrial equipment.

In the case of Capital Cooking Equipment, a manufacturer of high-end cooking indoor and outdoor appliances for residential applications, MMIs are featured on several models of equipment, notably electric wall ovens and dual-fuel ranges.

“These sophisticated products require controls as opposed to just mechanical pushbuttons, knobs and dials,” Kitabayashi explains. “Essentially, they require an interface between the operator and the control system to allow various kinds of input.”

To provide customers with a choice of MMIs, Capital Cooking offers some models of ranges with a membrane switch panel composed of deformable switches that make contact with the control system. Some of the oven products feature a passive touch-capacitive glass panel that communicates with the control system via software.

To handle the design of its more complex interfaces Capital Cooking enlisted the expertise of Jayco mmi (man-machine interface), in Corona, California. With 35 years of experience, the company has been designing, engineering, and manufacturing a wide variety of interface products, specializing in custom control panel assemblies, keyboards, keypads, and flat panel (membrane) switches for military, defense, aerospace, medical, security, communications, industrial, and commercial applications. It is reported to be one of only a few suppliers in the U.S. capable of handling extremely complex design work, utilizing virtually any available interface technology.

“With over 2,000 projects completed, we know that the key to a successful product is to understand the human connection, both with the interface itself, and with our clients and partners,” explains Hemant Mistry, Jayco president.


Virtual prototyping, which employs the use of computer-aided design and engineering software, enables the interface development expert to both generate and validate a “virtual” interface design before creating a physical prototype, a capability that can save product manufacturers sizable amounts of time and money.
Photo courtesy of Jayco mmi.

Kitabayashi has worked with Jayco on interface projects for over 15 years, seven of them while at Capital Cooking Equipment. “Most recently we worked with them on the glass touch-capacitive panel for a residential product,” he said. “They formed a team with experience in that type of interface, including a software developer to create a program that would ensure that all signals got to their proper destinations.”

Kitabayashi adds that Jayco also performed some fine-tuning to adjust the sensitivity of the glass panel. If the switch settings are too sensitive, then the users could set them all off by simply walking past the equipment. If the switches—either deformable or glass panel—are not sensitive enough, then they won’t activate (or deactivate) when necessary.

Developing a successful machine interface involves other design subtleties such as ergonomics, psychology, and other “user-centric” considerations. Plus, there are a host of available materials and interface technologies to choose from, a need to perform in harsh environments, and, increasingly, the need to fit the most effective HMI within extremely limited space on smaller products.

Whether the interface is displaying information, collecting data, or controlling operations, it may require special design consideration, such as ruggedized features or the integration of multiple elements into one. These are indicative of the many design challenges at the higher levels of complexity shared by HMIs and MMIs.

Avoiding Design Pitfalls

With growing demand for more complex software and touch screen technology, particularly when developing professional equipment for critical applications, designing the most appropriate HMI or MMI is becoming, in many respects, even more challenging. With such a dizzying array of solutions available, it is extremely difficult for most product designers to determine which switch and display technologies are appropriate, which control modalities should be used, which functions require direct user access, which materials and construction techniques are optimum, and what engineering constraints influence both design and costs.

Still, the product developer may be tempted to design the interface on a build-to-print basis, turning over the plans to an interface manufacturer to build the control panel or keypad or other device.

“There are serious challenges involved when customers build-to-print their own interface designs,” says Keith Heinzig, vice president of engineering at Secure Communication Systems, Inc. (Santa Ana, California). “Those include possible errors requiring redesign and additional time and money. Also, depending on the application, reliability is always a key constraint.”

Also, from an interface developer /manufacturer’s perspective, the built-to-print approach carries with it avoidable risks.


Graphic illustrates the layers of a human-machine interface (HMI). Given the complexities involved in interface design, many product designers and engineers are turning to interface specialists to support the design of their products.
Photo courtesy of Jayco mmi.

Jayco’s Mistry says that the most efficient and effective approach to interface design usually involves a team approach that includes the product engineering staff, as well as the interface supplier. The latter would provide consulting and design expertise based on the experience and diversity of interface hardware and software engineers, human factor experts, product designers, and manufacturing expertise. This consultative process can reduce product development time and costs while solving complex problems with superior solutions and packaging.

“By working together, the team can ensure that all of the relevant ideas are thoroughly explored, and that various manufacturing issues are taken into account,” Mistry explains.

“I think the best interfaces are simple and intuitive,” he adds. “But that is not easy. What is required is a thorough understanding of the application, an understanding of the environment that the product is going to be used in, and the technologies that are available to achieve the end.”

To complement the consultative approach, Mistry’s firm goes a step further by providing a digital or virtual prototype so that the customer can see precisely the proposed solution as well as how it will fit and operate in the end-user’s environment.

Virtual prototyping, which employs the use of computer-aided design and engineering software, enables the interface development expert to both generate and validate a “virtual” interface design before creating a physical prototype, a capability that can save product manufacturers sizable amounts of time and money.

For example, increasingly, there is limited space available for locating an interface on a product. Creating a virtual prototype can ensure that everything can be packaged properly without fit or interference issues, or manufacturing or reliability problems.

Anticipating Challenges

One of the best reasons to consult with an interface specialist before designing the interface is the need to meet several challenges that are “moving targets” as products and application requirements evolve.

For example, ensuring that interface devices, including enclosures and attachments, are ruggedized for environmental conditions should also be a vital concern. In the case of some applications, this includes protection against corrosive environments, providing for ultra-rugged applications that require military-grade shielding, protection against shock or vibration, contaminant sealing, daylight readable, night vision lighting, and extended-life grade products.

Also, it is ideal to get a complete interface assembly from a sole supplier, rather than only the interface components. This will help to ensure proper integration, provide plug-and-play connectivity, and save the customer from having to deal with the additional suppliers. For instance, a specialist can supply the entire assembly through to electronic communications from display to host computer, including encryption if required.

Ed Sullivan is a freelance writer based in Hermosa Beach, California. He has researched and written about high technologies, healthcare, finance, and real estate for over 25 years.

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