Capacitive controls

As a control element or in combination with a touch screen, capacitive buttons can be customized individually according to customer requirements. The simple and intuitive operation with slight touch reflect the same principle of operation as a touch screen.

An input system with fully enclosed surface made of glass, Plexiglas or polyester provides protection against dirt and liquids. The corresponding interface can be designed according to specifications using both digital and screen printing. Various types of operations can be implemented in the form of buttons, rotary wheels or sliders. Illuminated capacitive controls provide optimal visibility even in unfavorable lighting conditions.

Due to our SideLED technology, individual keys can be illuminated in different colors. Specially engineered surfaces make capacitive controls particularly resistant and create optimal conditions for harsh application environments.

How does it work?

Capacitive controls such as buttons, wheels or sliders function similar to capacitive touches. Again, it is possible to set up the components based on the two detection methods, self-capacitance and mutual capacitance.
In order to do so, conductive fields are applied to film or FR4. When, for example, a finger approaches or touches the area, electrical charge is withdrawn from the circuit which is detected as a contact.

Several ways exist to implement capacitive controls. They can be printed, for example, as highly transparent surfaces in almost any shapes on transparent polyester film. This allows the application of input elements on curved surfaces. Furthermore, it is possible to illuminate the entire surface of these capacitive controls.

Another way to implement such input systems is to produce them as copper pads on circuit boards. This provides the advantage that the required electronic evaluation unit and additional components can be applied to the same board. Due to its proximity to the electronic evaluation unit, these systems are also less susceptible to interference.

Pros and cons

Pros

  • Fully sealed surface possible
  • Over million switch cycles with constant trip characteristics
  • minor attrition
  • simple and intuitive operation
  • Suitable for operating conditions exposed to high-risk of vandalism
  • Ideal for visually high-quality applications

Cons

  • Depending on settings, operation not possible with gloved hands
  • Electromagnetic fields as well as moisture and temperature fluctuations may cause malfunctions

Applications

Due to the innovations in input devices in the consumer sector – smartphones, tablets, etc. – the acceptance of the capacitive technology increases in other areas as well. Furthermore, the technology-related deficits – e.g. electromagnetic interference, humidity and temperature fluctuations – can usually be corrected or alleviated through a combination of software and hardware adjustments. Capacitive controls can be implemented in various ways. Mechanical keys as well as mechanical position sensors can be replaced in the form of sliders and wheels. Another highlight already known through membrane keypads is the “varnish effect” for inactive buttons and capacitive touchpads. Among others, capacitive controls are now used in the following areas:

  • Industrial PCs
  • Household appliances (e.g. washing machine / dryer / stove)
  • Control panels (e.g. in public transportation)
  • Input devices in the public sector
  • Medical applications
  • Automotive industry