Capacitive Touch Switch for Automotive Applications 5

When two capacitive sensors are placed close to each other, both can detect if a finger presses between them. This effect can be utilized to achieve analog finger position touch sensing. A scroll bar consists of a group of adjacent sensors designed so that a single finger affects multiple sensors. The capacitive changes from all affected sensors can be used to calculate the center of mass (i.e., centroid). This value accurately determines the finger's position. Figure 6 illustrates the construction method of such a scroll bar.  diode

When using a scroll bar, it is crucial to select an appropriate sensor shape to facilitate easy finger interaction with multiple sensors. One potential application of the scroll bar is cruise control. Imagine a series of transparent sensors placed above the speedometer reading. By roughly positioning the display indicator between 55 mph and 60 mph, the cruise speed can be easily set to 57 mph. Dimming and/or volume control are also viable applications for CapSense scroll bars. Capacitive switch sensors can be integrated into the front of any measuring instrument. As automotive control panels become more complex, fitting all controllers within limited available space has grown increasingly challenging. The steering wheel surface has long been an overlooked area. This makes sense, as it is often where driver airbags are installed in many vehicles—no one wants a cluster of mechanical switches to scatter rapidly across their face and chest when the airbag deploys. Capacitive sensors lack mechanical components; they are merely traces coated on the back of the airbag cover. If electroplating is not desired, a thin flexible circuit can be mounted directly behind the airbag cover. Another underutilized control area is the window section. What if the defogger controller were placed directly on the window itself? Today, windshield wiper controllers are often mounted on the windshield. Envision a digital door lock installed precisely above the window on the door handle. The owner touches the sensor to input the correct combination. The sensor can be fabricated using glass-printed circuit technology or transparent embossing. These sensors can be shaped to resemble a traditional keypad, but why stick to conventional forms? They can instead be designed as part of the car's logo or model name, as shown in Figure 7.   diode