Working Principle of Light Touch Switch under Different Structures
Release time：2019-01-07 Clicks： Click
Today, I will introduce to you the working principle of light touch switch under different structures. What are the specific contents? Let's look at the introduction below.
The structure of light touch switch can be divided into five parts: cover plate, button, shrapnel, base and pin, in which button refers to the place where external force is applied; shrapnel is the key component of light touch switch, and the breaking of switch is caused by the force change of shrapnel; pin refers to the connection between light touch switch and circuit, generally five pins, two pairs of pins, and one pin for grounding operation. When the switch is properly loaded, four pins are turned on to make the circuit turn on, and when the switch is not properly pressed by external force, the four pins are not connected in two groups, which makes the circuit in a state of disconnection.
There are two kinds of light-touch switches according to different principles. One is to use metal shrapnel to complete switch-on and cut-off state switch. This kind of light-touch switch has a good handle, accompanied by clicking sound when pushing button to a certain extent; the other is to use conductive rubber to complete switch-on and cut-off state switch. This kind of switch has a good handle, but a large contact resistance, which is about the top. 10,000 times of species. Tact Switch
1. The function of the open contact in the four-legged light touch switch is that when the pressure is applied to the open contact, the circuit will be turned on; when the pressure is removed, the original closed contact will be restored, that is, the so-called disconnection. This pressure is the action of opening and closing the button with our hands.
2. When the pressure is withdrawn, the four-legged lightly touching switch will be closed. The internal structure of the four-legged lightly touching switch relies on metal shrapnel to protect the stress situation and realize the connection and disconnection.
3. The principle of four-legged touch switch is related to its structure. For example, 220V AC passes through the bulb H and rectifier bridge, and then becomes DC pulsating voltage, which acts as forward bias, and is added to SCR VS and R branches.
1. In daytime, when the brightness is greater than a certain degree, the photodiode D presents a bottom resistance state of less than 1K, which makes the transistor V cut off, and its emitter has no current output, and the one-way thyristor VS is blocked because of no trigger current. At this time, the current flowing through the bulb H is less than 2.2mA, and the bulb H cannot emit light. Resistor R1 and voltage regulator diode DW make the bias voltage of triode V not exceed 6.8V and protect triode.
2. At night, when the brightness is less than a certain degree, the photodiode D presents a high resistance state (> 100K), which makes the transistor V forward-conducting, and the emitter voltage is about 0.8V, so that the thyristor VS triggers and turns on, and the bulb H emits light. RP is a brightness selection element for switching in the morning or evening.
4. Whatever the structure of the lightly touched switch, the common feature of the four-legged lightly touched switch is that it has four pins. The advantage of the four-legged lightly touched switch over the ordinary lightly touched switch is that it can be soldered firmly. Everyone can use the four-legged lightly touched switch to adjust and control accurately.
When we press the button of the switch, the shrapnel of the switch is deformed by the elastic force and contacts the welding strip downward, which makes the two groups of pins of the switch turn on, thus making the circuit turn on. When we withdraw the external force, the shrapnel deformation restores the original state, and the two groups of pins of the switch are no longer turned on, thus making the circuit turn off.