Capacitive touch switch

Capacitive sensing touch switch needs stable single-wire power supply and stable and reliable touch sensor chip, so as to meet the functional requirements of anti-mistouch, anti-various electromagnetic interference, load interference, environmental interference, and even waterproof and dustproof intelligent touch switch.

1. Rationale

Capacitive switch is mainly composed of two adjacent circuit board poles, between the two boards will generate capacitance. When the finger is close, the equivalent of a parallel capacitor will be coupled to the sensor. When the finger is placed on the sensor, the capacitance will increase. The capacitance will decrease when you remove it.

The elements of constructing capacitive switch include: capacitor, capacitive measuring circuit system, and local intelligent device that converts leisurely value into inductive state. The capacitance of a typical capacitive sensor is between 10-30PF. Generally speaking, the coupling capacitance of a finger touching the sensor through 1mm insulation layer is 1-2PF. The thicker the insulation layer, the lower the coupling capacitance. If you want to detect the touch of a finger, you must be able to detect the capacitance of less than 1% of the sensor circuit.

Sensor charging current

The discharge current of the sensor, the influence of switch sensitivity, the influence of touch induction switch PCB pattern, the influence of insulation material, the length of wire running, the longer the wire running, the greater the parasitic capacitance, which affects the normal operation of the switch. Influence of power supply voltage and design of touch induction switch