The ActiveTouch Technology

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The basic principle is that a material capable of supporting shear and torsional mechanical waves at ultrasonic frequencies can have those waves trapped or localized by contouring or bonding decals to its surface. These trapped energy regions are set into motion with transducers and act as high quality resonators.
	When the surface of a switch plate is contoured as depicted to the left, it creates raised regions or Resonant Cavities that trap ultrasonic energy in accordance with energy trapping theory. The switch operates with ultrasonic energy, and the metal plate acts as a very effective shield. Despite the use of acoustic resonance, vibration in these sensors and mechanical vibrations from external sources do not influence sensor performance.
When a resonator is set into vibration at about 1 MHz by a properly positioned ultrasonic transducer, a twisting motion is induced. The motion is confined to the shape of a cylinder, and it extends through the thickness of the metal. This twisting motion is known as "trapped torsional mode”.
	Motion is initiated by an electrical impulse to the transducer, then as the vibration decays or "rings down" like a bell that has been struck. A finger or gloved hand touching the front surface at the end of a vibrating cylindrical region dampens the vibration and reduces the region's ring-down time. This reduction in ring-down time (decay rate) is detected with an inexpensive microcontroller which is easily multiplexed for multiple switch positions.
When the time to a threshold value is lower than the preset value, the microcontroller is programmed to indicate switch actuation. This is a continuous process occurring every few milliseconds.

ActiveTouch switches trap ultrasonic energy in localized regions known as “resonant cavities”. These cavities are created by contouring the back surface or with bonded-on decals. Depending on the application, the surface is contoured by machining, etching, stamping, or sand blasting a “moat” around the periphery of the cavity. Another approach is to machine “domes” in the metal (with an end mill, for example) which also creates the required cavity. A resonant cavity defines the switch’s periphery and its active area.

Our engineers & industrial designers can design the correct geometry to match your aesthetic and performance needs. With ActiveTouch, product designs are not restricted or confined by a narrow range of available materials and thicknesses. From sheet metal to steel-plate, any level of durability can be created.

Material thickness may range all the way from wafer thin up to 0.5” (12.7 mm) Materials may include die cast, machined, ground, rolled, and stamped ferrous and non-ferrous metals. Even leading edge architectural materials including brushed, plated, and coated aluminum; carbon and stainless steel; ceramics, stone, granite, glass, and specialty plastics may be used.

In addition, switch fascia may be engraved, printed, etched, or otherwise finished providing designers great latitude and broad opportunity when incorporating switches into a wide range of aesthetic design. What’s more, ActiveTouch switches can be conveniently integrated into existing enclosures without affecting structural integrity. And if desired, switch locations may even be hidden from the user.

Resonant cavities determine the area that, when touched, will cause actuation. Any number of customer-defined shapes, sizes, and active area configurations are possible as small as 0.12” (3.048 mm) in diameter and as close together as 0.015” (.381 mm) between center. ActiveTouch switches can easily be used in stand-alone applications or be incorporated into panel-mounts or applied to curved surfaces.

Other desirable design options include contouring a panel’s front surface to give a finger a positive fit, employing inexpensive overlays to provide a conventional keyboard response which can also be discarded or removed for aggressive sterilization, incorporating Braille legends, and using other locating aids. All are easily implemented. Illumination can be provided by clear, epoxy-filled channels formed in the metal in the center or adjacent to each switch position, or by a light guide plastic overlay bonded onto the top surface.

Active Area Customizations
• Size
• Shape
• Proximity to each other
• Proximity to material edges
• Recessed user interface
• Embossed user interface
• Material overlays
• Integration into existing designs