Abstract
Touch sensing is a fundamental approach in human-to-machine interfaces, and is currently under widespread use. Many current applications use active touch sensing technologies. Passive touch sensing technologies are, however, more adequate to implement low power or energy harvesting touch sensing interfaces. This paper presents a passive touch sensing technique based on the fact that the human body is affected by the surrounding extremely low frequency (ELF) electromagnetic fields, such as those of AC power lines. These external ELF fields induce electric potentials on the human body—because human tissues exhibit some conductivity at these frequencies—resulting in what is called AC hum. We therefore propose a passive touch sensing system that detects this hum noise when a human touch occurs, thus distinguishing between touch and non-touch events. The effectiveness of the proposed technique is validated by designing and implementing a flexible touch sensing keyboard.
Highlights
Touch sensing technologies are used in many applications, comprising smartphones and tablets, laptops, information kiosks, etc
Examples include technologies based on infra-red sensing elements [1,2,3,4], resistive [5,6] and capacitive touch panels [7,8,9], cameras [10], the acoustic and deflection characteristics of touch panels [11,12,13], and others [14,15,16]
The touch screen interface is built or constructed by rows and columns of transparent wires made from indium tin oxide
Summary
Touch sensing technologies are used in many applications, comprising smartphones and tablets, laptops, information kiosks, etc. One of the widely used techniques is the mutual capacitive method, which is used in almost all smartphones and tablets [17] In this method, the touch screen interface is built or constructed by rows and columns of transparent wires made from indium tin oxide. An example of a passive touch technique is acoustic pulse recognition where sound wave receivers are used to detect a touch and no transmitters are required. Some low power passive touch sensing techniques have been proposed, for which driver circuits are not required. Some of these techniques may not be suitable to detect the touch of human fingers [20,21]. We present a flexible touch keyboard design as an example of a low power passive touch interface based on the humantenna technique.
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