How a touch switch's voice chip works
10 Jan 2020 -
About the principle of touch switch The following is my understanding of personal professional: The principle of touch switch is triggered by the human body's induced voltage, because in our environment many electromagnetic waves will cause the human body to generate induced voltage. Because of the induction voltage, the input triode (usually a high input impedance COMS tube) can be used to trigger the touch switch to make it conductive, thereby controlling the circuit switch.
There are many types of touch switches, here are some points from my finishing office:
1. Two-piece conductive switch: the front end is two electrode pads, and inside is an amplifying circuit, which amplifies the current formed in the two pads when a finger touches it, and drives the subsequent circuit to realize the switching or control function.
2. Resistive film or conductive film pressure-sensitive switch: This switch is realized by a three-layer structure. A support grid is sandwiched between the upper and lower conductive sheets. Computer keyboards and ordinary household lighting switches generally have this structure. Switches are still in the same category, but people can barely feel the stroke.
3. Mechanical tact switch: The switches and button switches that are common in our life are only improved after the short stroke and the distance to be pressed is small.
4. Capacitive finger touch switch: This is a switch commonly used in our voice chips. A capacitor formed by a specially shaped PCB (printed circuit board) is used as a trigger condition for touch. Generally, a rigid FR-4 substrate is used. The capacitance base of the capacitive touch panel made of material is small, and the change of the capacitance after the finger is obvious, and the effect is good. A SLOPE circuit or a frequency-voltage conversion circuit is used to determine the capacitance change, and finally determine whether there is a finger touch.
As for the voice chip, various touch switches can be designed, and the application fields are more extensive, such as: digital products, electronic voice toys, educational electronics, advanced gift boxes, and so on.
