Choosing the PSoC 4 CapSense Overlay – KBA227569

Version 5

    Author: RyanZ_36          Version: **

     

    Translation - Japanese: PSoC 4 CapSenseオーバーレイについて- KBA227569 - Community Translated (JA)

    Materials with relative permittivity between 2.0 and 8.0 are well suited for CapSense® overlay, such as glass, acrylic and PET film. Conductive materials interfere with the electric field pattern. Therefore, you should NOT use conductive materials(such as metal material) for overlay. You should also avoid using conductive paints on the overlay.

    Table 1 Relative Permittivity of Overlay Materials

    Material

    Relative Permittivity

    Air

    1.0

    Formica

    4.6 – 4.9

    Glass (Standard)

    7.6 – 8.0

    Glass (Ceramic)

    6.0

    PET Film (Mylar®)

    3.2

    Polycarbonate (Lexan®)

    2.9 – 3.0

    Acrylic (Plexiglas®)

    2.8

    ABS

    2.4 – 4.1

    Wood Table and Desktop

    1.2 – 2.5

    Gypsum (Drywall)

    2.5 – 6.0

    The thickness depends on different applications and overlay materials. The following table lists the recommended maximum thickness of acrylic overlay for different CapSense widgets.

    Table 2 Maximum Thickness of Acrylic Overlay

    Widget

    Maximum thickness (mm)

    Button

    5

    Slider

    5

    Touchpad

    0.5

    For other materials, convert the thickness with using relative permittivity.

    For example, the recommended maximum thickness of glass (ceramic) should be

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    Then we can get the recommended maximum thickness of glass (ceramic)

    Table 3 Maximum Thickness of Glass (Ceramic) Overlay

    Widget

    Maximum thickness (mm)

    Button

    10.71

    Slider

    10.71

    Touchpad

    1.071

    Reference Document:

     

    AN85951 - PSoC® 4 and PSoC® 6 MCU CapSense® Design Guide