Epec's Blog | Electronics Manufacturing Solutions

It is not often we build an electronic device without any sort of prototyping, but it can happen given the nature of the project and the deadlines being met. If a customer needs a Human-Machine Interface (HMI) to hit the floor in 2 months, the time to develop and build a prototype is strained as both the customer and design engineers will want to test it and provide feedback.

Front panels, bezels, and other types of human to machine interface equipment use several circuit technologies to operate. These circuit types usually involve some form of printed or etched traces using conductive materials like copper and conductive ink. These custom layouts are routed across insulating sheets and films, eventually becoming circuit boards and flex circuits. Dome switches, LEDs, and touchscreens can be added to these everyday circuit boards, bringing them to life as a high-technology HMI solution.

The use of capacitive touch switch technology is widespread and becoming more frequent each day. Capacitive touch switches are common on thousands of everyday devices including gas station pumps, smartphones, lamps, automobile dashboards, and even the smart speaker in your home.

The use of liquid crystal displays (LCDs) in user interface assemblies is widespread across nearly all industries, locations, and operating environments. Over the last 20 years, the cost of LCD displays has significantly dropped, allowing for this technology to be incorporated into many of the everyday devices we rely on.

As a premier supplier of human-machine interface (HMI) solutions, our engineers work with and design several types of membrane switches. From tactile and non-tactile response switches to the emerging technology of capacitive touch switches, we have provided proven quality for our customers depending on their needs.

Keypads that utilize dome switches, silicone elastomer keys, or tactile switches rely on actuation force as a critical feature to define how much load is required to close the normally open switch. In this context, force is a vector acting normal to the keypad surface and is usually defined in grams (g) or pound force (lb_f).

If you were to ask 5 separate people to explain the definition of keypad, likely you would receive 5 completely different answers that all center around the same basic concept. According to Wikipedia a keypad is a set of buttons arranged in a block or "pad" which bear digits, symbols or alphabetical letters (source https://en.wikipedia.org/wiki/Keypad). While this definition is correct, when communicating to a potential user interface supplier the term keypad requires further elaboration.

In this blog post you can view two videos that go into detail about the functionality of the human-machine interface (HMI) product sample and an overview of how capacitive touch membrane switches work. The transcription of both videos is also provided below. Take note that the transcriptions have been edited for better readability.

As capacitive touch human machine interface (HMI) assemblies become more popular, both designers and users are becoming more familiar with the technology as it replaces traditional mechanical HMI products. These capacitive touch HMIs can be used in extreme environments, with users wearing gloves, and can operate reliably for years.

Just as a mechanical HMI (membrane switches, tactile switches, etc.) relies on the overlay material properties to determine system function, capacitive touch HMIs rely on the overlay material properties to drive capacitive touch sensitivity and overall system performance.

When our customers are in the preliminary stages of launching a new SMART HMI project, they typically reach out seeking advice on the best way to start. With what can amount to a near infinite number of HMI design options and system feature combinations, brainstorming an embedded firmware project can quickly become overwhelming. Where does one begin? How does the firmware work? What level of detail is required now?