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Key-judging method for capacitive touch keys

A capacitive, button technology, applied in electrical components, electronic switches, pulse technology, etc., can solve problems such as complexity, high PCB board requirements, and poor anti-interference ability.

Active Publication Date: 2010-12-08
SINO WEALTH ELECTRONICS
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0007] The purpose of the present invention is to provide a capacitive touch key judgment method to solve the existing technical problems such as low sensitivity, poor anti-interference ability, high requirements on the PCB board, and complicated software and hardware processing.

Method used

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  • Key-judging method for capacitive touch keys

Examples

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Embodiment 1

[0027] Apply the existing touch key judgment method, that is, the method based on the absolute value of the equivalent capacitance of the key, to the touch key system provided in the above embodiments. Since this key judgment method is a prior art and has different data processing methods (for example, a Chinese patent application with application number 200810006684.0 discloses an implementation method), therefore, only a brief overview is given here.

[0028] Such as figure 1 and figure 2 As shown, Cx is the equivalent capacitance of the touch button, and forms a switched capacitor circuit with the logic control switches SW1 and SW2. Wherein, the logic control switches SW1 and SW2 can be controlled by the same clock inside the MCU, and they alternately present closed and open states with the same frequency and a fixed time difference. According to the switch capacitance characteristics, the logic control switches SW1 and SW2 and the equivalent capacitance Cx of the touch ...

Embodiment 2

[0037] Similarly, if figure 1 and figure 2 As shown, Cx is the equivalent capacitance of the touch button, and forms a switched capacitor circuit with the logic control switches SW1 and SW2. Wherein, the logic control switches SW1 and SW2 can be controlled by the same clock inside the MCU, and they alternately present closed and open states with the same frequency and a fixed time difference. According to the switch capacitance characteristics, the logic control switches SW1 and SW2 and the equivalent capacitance Cx of the touch key can be equivalent to the resistance Rx. And satisfy:

[0038] Rx=1 / (fs×Cx) (1)

[0039] Wherein fs is the switching frequency of the touch key system, which can periodically switch the logic control switches SW1 and SW2.

[0040] The power supply VDD periodically charges and discharges the charge and discharge capacitor 220 through the switch equivalent resistance Rx. Before and after the key is pressed, the change of the equivalent capacitan...

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Abstract

The invention discloses a key-judging method for capacitive touch keys, comprising the steps of: setting an entropy coefficient; scanning keys to obtain a count value of the first charging time of a charge and discharge capacitor; dividing the count value of the first charging time into the entropy coefficient to obtain a first relative quantity reflecting the equivalent capacity of a touch key; scanning the keys again to obtain a count value of the second charging time of the charge and discharge capacitor; dividing the count value of the second charging time into the entropy coefficient to obtain a second relative quantity reflecting the equivalent capacity of the touch key; obtaining a difference value between the second relative quantity and the first relative quantity, and judging the keys by utilizing the difference value. In the key-judging method, the keys are judged by obtaining the relative variation quantity of the charging time of the charge and discharge capacitor C1. Therefore, the difference of stray capacitance on a PAD of a PCB cannot influence key judgement. The method is simple in realization and greatly reduces the requirements and the difficulty for PCB and software algorithm treatment.

Description

technical field [0001] The invention relates to the field of touch button manufacturing, in particular to a capacitive touch button judgment method. Background technique [0002] Touch control can be divided into various control methods such as radio wave type, resistive type, optical type, capacitive type, inductive type and electromagnetic type according to different principles. Each control method has its own advantages and disadvantages and applicable occasions. Among them, the capacitive touch key is suitable for many household appliances due to its relatively simple circuit, which only needs a microprocessor and some peripheral circuits to realize the touch detection and control of the key. [0003] The basic principle of a capacitive touch button is a relaxation oscillator that is continuously charged and discharged. Without touching the switch, the relaxation oscillator has a fixed charge and discharge cycle, and the frequency is measurable. If you touch the switc...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H03K17/96
Inventor 荆玉珂许成珅曹中信黄智
Owner SINO WEALTH ELECTRONICS
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