Touchscreen2010_Pres - Touch Screen Technologies ECE 317...

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Touch Screen Technologies ECE 317 Nick Letterly, Elise Stockl, Fei Wang
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Capacitive Touch Screens Most popular type of touch screen MP3 players, cell phones, computer monitors Engineers choose because of ease of use, cost reductions, and unique interface opportunities Many types, such as surface capacitance, project capacitance, mutual capacitance, and self capacitance
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Technical Overview Based on the ability for a finger to hold a charge; your finger is in series with the signal Consists of an insulator that is coated with a conductor, such as indium tix oxide, that holds the initial electrical charge. Can be explained by Q=CV, where Q is charge, C is capacitance, and V is voltage. Finger enters into devices electrical field, and your finger acts as a conductive surface
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Technical Overview The additional charge storage capacity your finger can take is known as your finger capacitance The device measures the amount and position of the change in capacitance to detect your finger’s position The current between your finger and the device is an AC current Current reverses direction, alternates between finger and device; as demonstrated by a sine wave.
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Advantages No effects from non- conductive materials. Flexibility in implementation. Much more responsive than competing touch screen technologies . Disadvantages No effects from non- conductive materials. Less accurate than some competing touch screen technologies. Water/moisture greatly reduces performance of touch screen.
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Mutual Capacitance - iPhone This technology allows for gesture and multi-touch. A coating of current carrying lines, which create a grid, are layered on top of typical capacitance sensing lines. Allows for measurement of
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This note was uploaded on 01/24/2012 for the course ECE 317 taught by Professor Peck,t during the Spring '08 term at University of Illinois, Urbana Champaign.

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Touchscreen2010_Pres - Touch Screen Technologies ECE 317...

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