Introduction to the Working Principle of Four-legged Touch Switch
Release time：2019-01-18 Clicks： Click
What's the working principle of the four-legged touch switch we use? We'll give you some details.
Four-legged touch switch, as its name implies, has four-legged touch switch, four-legged touch switch is always widely used in daily products, which occupies a relatively large part. The four pins here refer to the four pins that touch the switch lightly. The four pins are two groups of switches. When pressed, two groups of switches are simultaneously energized. When opened, two groups of pins are opened at the same time. Some people say that the four pins are for soldering the circuit board firmly. In fact, this understanding is not wrong.
Whether it is a four-legged lightly touch switch or other lightly touch switch, its working principle is relatively similar, partly because the number of pins is different, the switch is different, so the basic working principle of the four-legged lightly touch switch is different. What is the working principle of the four-legged touch switch?
Working Principle of Four-legged Touch 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 When the pressure is withdrawn, the four-legged lightly touching switch will be closed.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, which makes the thyristor VS trigger and turn on, and the lamp 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.