Weekly Reading: New Capacitive Touch, Opening a New Milestone of Keyboard Interaction

Compared with traditional touch buttons, the new touch function buttons can be sensed through 10mm thick acrylic materials or wooden boards, have stronger durability, and do not require touch sensing springs. Compared with light touch buttons, it has enhanced durability and is resistant to dirt and water, which can greatly reduce the error rate of keystrokes.

The new capacitive touch function button can realize a seamless panel, so when cleaning stains, it can be simply wiped, which is very easy to clean, saving time and effort. In addition, it can also realize proximity sensing within a range of 300mm, and the anti-interference degree has passed the IEC61000 4-3/4-6 Level 3 test.

The new touch function keys support two working modes: capacitive self-sensing mode and capacitive mutual-sensing mode. The mutual-sensing mode can increase the number of touch keys through the key matrix and enhance the waterproof capability of the touch keys.

As shown in the figure above, it is a capacitive self-sensing method. The self-sensing method detects the increase in capacitance. When the key is pressed, the capacitance will increase. A wet surface will also increase the capacitance rate, causing false key presses, as shown in the figure below.

As shown in the figure below, in the mutual induction mode, the decrease in capacitance is detected to determine whether the button is pressed.

Since the capacitance increases on a wet surface, the buttons can be correctly identified even on a wet surface, thus avoiding touch misoperation in the capacitive self-sensing mode.

The integration of the microcontroller makes the hardware design more concise, and the easy-to-use development tool that automatically adjusts the touch sensitivity allows users without professional knowledge or development experience to implement a capacitive touch sensing system.

Since the new capacitive touch peripherals can sense through 10mm thick acrylic, wood or other materials, customers can more freely choose surface covering materials, such as thicker materials, and can also use them through gloves, etc., to achieve solutions that can be applied to many products.

Secondly, in the mutual inductance mode, the waterproof performance of the touch button can be improved, so that a more complex touch button interface for use on wet surfaces can be designed.

In addition, the new touch buttons can also be made into a film type, so touch buttons can be realized on curved surfaces.

Through some of the above solutions, touch buttons can be applied to many smart devices, such as smart electronic locks, smart remote control desktops, etc. The new capacitive touch peripherals of the RX100/RX200 series microcontrollers can reduce product components, eliminate the need for physical buttons, significantly reduce product costs, and can be used in various complex designs.

Renesas Electronics offers four product series to suit different applications, namely RX113, RX130, RX230, and RX231.