Constructing a capacitive sensor using springs 5

Install the spring on the PCB

Due to the high lateral sensitivity of the spring, the distance between adjacent spring sensors should be as far apart as possible to avoid erroneous detection. If the sensor spacing is small, an additional shielding layer can be added. Figure 13 provides an example of spring installation.  diode

The requirements for the spring sensing area are the same as those for the solid-state button. If the cover layer is thick, the spring diameter must be at least 2 to 3 times larger than the thickness of the cover layer, and the distance between the PCB and the cover layer must be 5 millimeters or more.

Figure 14 shows the bottom projection (footprint) of the spring. Do not place a solid ground beneath the spring, as this will increase the complexity of spring soldering and raise the native capacitance of the sensor.

Springs can also be utilized to develop additional functions, including:   diode

The use of backlighting

Sensors typically require backlighting. Using a spring as a sensor allows for internal placement of LEDs to achieve uniform front panel illumination. Two types of backlighting can be achieved:  1. LEDs installed at the top of the panel provide a diffused backlight effect.  2. LEDs installed at the bottom of the panel direct light upward through openings, creating a focused effect.  Broad scattered light is suitable for backlighting front panel icons, while narrower focused light is ideal for status indicator designs. Dual-color LEDs are highly suitable for applications requiring both backlighting and button status indicators.   diode