Capacitive sensing
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CapSense is a widely used capacitive sensing solution developed by Cypress Semiconductor. Capacitive sensing replaces mechanical buttons, membranes, and other moving parts with a proximity-sensitive interface. Two electrodes are covered by an insulating stratum—frequently plastic or glass—and, when a finger touches the surface, a capacitance is created. CapSense understands this change in capacitance and performs a programmed function. The entire process requires no contact (what seems to be “touch” sensing is in fact proximity sensing—with the maximum sensible proximity set to the precise thickness of the plastic or glass overlay) and CapSense therefore provides a robust control mechanism not subject to dirt, dust, wear, moisture, and other factors that limit the life of “legacy” control interfaces.
The CapSense solution is based on Cypress’s PSoC, a programmable system-on-chip that interprets touch inputs from the capacitive sensor. Since PSoC is a fully programmable controller, CapSense works with a wide variety of sensors, and the same CapSense can interpret dozens of buttons, touchpads, and variable sliders simultaneously. Because of this flexibility, many consumer electronics manufacturers who make frequent changes late in the product design process have adopted CapSense. Cypress reports that CapSense-based interfaces have replaced over 2.5 billion mechanical buttons and sliders, and, according to IMS Research, CapSense retains 70 to 80% of the market for cellular handset capacitive sensing functionality.
While simple applications of CapSense merely replace mechanical buttons with slimmer capacitive ones, more advanced technologies, including multi-touch and gesture-based touchscreens , are also premised on capacitive sensing. Boutique firms like Perceptive Pixel, as well as Cypress itself, market multi-touch solutions.
The most famous implementation of Cypress CapSense is in the iPod click wheel.
External links
- http://www.cypress.com/capsense/ – Cypress Capsense
- http://edageek.com/2007/11/09/cypress-psoc-capsense-2/ - Cypress' PSoC CapSense Solution Achieves 70% Market Share
- http://www.emsnow.com/newsarchives/archivedetails.cfm?ID=10207 – “iSuppli teardown reveals Apple's surprising choices for iPod nano” EMSnow