ST's Capacitive Touch Button Solution 1

Resistance is the opposing effect of a substance on electric current, known as the resistance of that substance. Materials with low resistance are called conductors, abbreviated as conductors. Materials with high resistance are called insulators, abbreviated as insulators.

Capacitive touch buttons, such as B capacitive touch buttons, are not only durable, cost-effective, and feature simple mechanisms for easy installation, but also waterproof and resistant to stains. Additionally, they can provide functions like rollers and sliders. However, B capacitive touch buttons also have many issues. Due to the absence of mechanical structures, all detection relies on minor electrical changes, making them highly sensitive to various interferences. ST has introduced a solution based on the STM8 series of 8-bit general-purpose microcontrollers for home appliance applications, particularly induction cooktops. A microcontroller (also known as a microprocessor or MCU) is a small computer composed of a series of simple circuits and modules that support CPU functions, such as crystal oscillators, timers, watchdogs, serial and analog I/O ports, etc. The chip includes non-volatile memory and OTP ROM for program storage, along with a minimal read-write program. The platform's capacitive touch sensing solution eliminates the need for dedicated touch chips, enabling B capacitive touch sensing functionality with just simple peripheral circuits, facilitating customer secondary development.  diode

2. Solution Introduction

ST's capacitive touch button solution detects changes in the B capacitance (CX) caused by human touch through the charging/ discharging time of a resistive-capacitive network formed by a resistor and the sensing electrode. The sensing electrode can be directly drawn on the PCB board in the form of buttons, scroll wheels, or sliders, or can be made as a spring component inserted into the PCB board. Even when covered by an insulating layer (glass, resin), it does not affect its detection performance.

The induction cooker heats food by utilizing the principle of magnetic field-induced current. During heating, a strong magnetic field is generated beneath the panel through a coil. When the magnetic flux lines pass through the bottom of the pot made of ferromagnetic material, the pot cuts the alternating magnetic flux lines, creating eddy currents in the pot's base that rapidly heat it, achieving the goal of cooking. In this solution, the STM8S105S4 (44-pin) is used as the main control chip for the key display board, managing the scanning of 13 buttons and controlling 24 LEDs   diode