Capacitive sensing provides a robust alternative to traditional mechanical switches. However, some applications cannot accommodate the physical implementation of a printed circuit board directly under an overlay or attached to the device case. Examples of such applications are "white goods" such as cooktops, washing machines, refrigerators, microwave ovens, and others, as well as various vehicle electronics, such as radio sets, TV tuners, dash boards, and seat occupant detectors. Metallic spring sensors may be used as an alternative to solid conductive sensors. This allows placement of the PCB at a distance from the overlay while providing a reliable sensor connection even under operating conditions of strong vibration or sharp temperature changes. In addition, springs provide added functional possibilities, such as backlighting, and combinations of mechanical and capacitive buttons. To read more, visit EDN.
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