The Working Principle of Capacitive Tactile Membrane Keyboard Panel Switch

In daily life, we often see some strange phenomena on some high-end electronics, that is, the whole device does not have a keyboard switch. When you touch a certain hidden area or a place with characters or patterns, the device will turn on. At this time, the surface displays the glowing keyboard name and location, which is very beautiful and also looks particularly mysterious, with a strong sense of technology.

Working principle of capacitive tactile membrane keyboard

The surface keyboard area of the capacitive keyboard product generally uses ABS or PC plastic shell itself or a whole piece of PMMA acrylic panel or a whole piece of tempered glass panel. The places with keyboard character patterns are made into a semi-transparent effect. When the machine is turned off, the internal LED lights do not light up, and the inside of the machine is dark. From the outside, the panel is a unified whole with the same base color. You cannot see the characters or patterns. After turning on the machine, the internal LED lights up, and light is emitted from the position of the characters or patterns, but other positions won't let light through, displaying keyboard characters or patterns.

The back of the panel is glued with a printed FPC flexible capacitive touch sensing soft circuit. All keyboard functions are transmitted through this soft circuit board. Each keyboard is connected to the main PCB with a wire to the keyboard area, without a circuit. The keyboard is equivalent to one pole of a capacitor, and the other pole of the capacitor is connected to the IC on the PCB circuit board. When your finger approaches the keyboard from a distance and then touches the keyboard, the entire process will cause the dielectric constant of the capacitor to change. The IC senses this change and knows which keyboard has a trigger command, giving the corresponding command to make the machine work.

Capacitive tactile membrane keyboard can penetrate insulation materials with a thickness of more than 8mm

It includes, but is not limited to, ABS, PC, PMMA, glass, etc. It can accurately and effectively detect the touch of the finger and ensure the sensitivity, stability, and reliability of the product. Since the keyboard does not need to make a switch stroke opening on the shell like a traditional keyboard, the sealing and waterproof and dustproof performance of this switch is better than that of a traditional keyboard. Similarly, because there is no traditional mechanical switch stroke, there is no frictional loss, which performs better in terms of sensitivity, stability, and reliability, and has a longer service life and lower later maintenance costs than ordinary traditional mechanical switches.

The capacitive keyboard should be close to the switch and has been widely used in audio panels, telephone control keyboards, instrument control panels, washing machine control panels, intelligent access control system control panels, various small home appliance panels (such as induction cookers, disinfection cabinets, microwave ovens, etc.), covering almost all application fields involving control keyboard operation panels of household appliances, handheld devices, industrial control, automotive electronics, military products, etc.