Constructing a capacitive sensor using springs 6

Combination of CapSense and mechanical buttons

The hollow space inside the spring can be used to install mechanical buttons (see Figure 15). Touching this button can only trigger the sensor, while pressing the button will trigger both the sensor and the mechanical button simultaneously. In this case, preparatory actions such as backlighting and prompts can only be provided when the sensor is working. The final action can only be executed when both buttons are triggered simultaneously. For example, in GPS navigation systems, touch buttons only display prompt information and can only be operated by pressing the button.

design paradigm 

Figures 16 and 17 show demonstration examples of household appliance application projects.

At the gap between the board and the cover layer, a spring can be used instead of a solid-state conductive sensor. When the thickness of the board is greater than a few millimeters, the sensitivity of the spring is not lower than that of a standard sensor. Meanwhile, using springs has the following advantages:  diode

·Provide a gap between the PCB and the cover layer.

·It can maintain different distances between the installed buttons and the board, making it easier to support curved cover layers.

·Due to the elasticity of the spring, it can provide reliable sensor function in the event of vibration or changes in the distance between the cover layer and the board (such as in washing machines).

·Very suitable for thicker cover layers.

·When the number of fragments and interpolation ratio are the same, it can provide better slider linearity than solid-state conductive sliders.   diode

·Easy to create sensor front panel backlight.

·Capacitive sensing can be combined with mechanical buttons to further improve the user interface.