Usually capacitive touch interfaces can’t be used with metal coverings, but Microchip’s Metal Over Cap overcomes this limitation:
As a user interface, capacitive touch has several advantages: it is low power, low cost, simple to implement, reliable mechanically, and it allows designers a great deal of freedom in the shape of the buttons. However, for all its advantages, the field effect nature of capacitive touch still has some limitations. 1. Standard capacitive touch systems normally do not work through metal coverings. 2. It requires special software to operate in environments with radiated and/or conducted noise. 3. Reading buttons in the presence of water or other contaminants can be difficult. 4. It is problematic for visually impaired users that rely on Braille. 5. It has trouble detecting a touch through gloves. Microchip?s new Metal Over Capacitive user interface system overcomes all of these limitations without compromising power consumption or design simplicity. This application note describes how to create an interface using the Metal Over Capacitive touch system.