Capacitive sensing
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CapSense is a capacitive sensing technique 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. This change in capacitance then triggers the execution of a pre-programmed function. The process relies on proximity based sensing, where the maximum sensible proximity is set to the thickness of the stratum overlay and does not strictly require physical contact as seen in touch sensing applications. It provides a control mechanism not subject to dirt, dust, wear, moisture, and other factors that can affect the life of other control interface technologies.
CapSense is based on Cypress’s PSoC, a fully programmable system-on-chip that takes input from the capacitive sensor. It works with a variety of sensors, and can interpret the inputs from multiple 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 interfaces based on CapSense have replaced over 2.5 billion mechanical buttons and sliders, and according to IMS Research, holds 70 to 80% market share for cellular handset capacitive sensing functionality.
While applications of CapSense can replace mechanical buttons with capacitive alternatives, other technologies such as multi-touch and gesture-based touchscreens are also premised on capacitive sensing. The Apple iPod click wheel is a well known implementation of CapSense.
External links
- http://www.cypress.com/capsense/ – Cypress Capsense
- http://electronicdesign.com/Articles/Index.cfm?AD=1&ArticleID=19873
- 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