Many friends are not very clear about the working principle of the four-legged light touch switch. We will introduce it to you here, hoping that you can understand and recognize these problems.
Four feet touch switch, as the name implies, with four feet touch switch, four feet touch switch in daily products are always commonly used, relatively occupied a large part. The four pins here are the four pins of the light touch switch. The four pins are the two groups of switches. When you press down, the two groups of switches are energized at the same time. And when you let go, the two groups are opened at the same time. Some people say that the four pins are for the purpose of soldering the circuit board firmly. In fact, this understanding is correct.
Whether it is a four-foot touch switch or other light touch switch, its working principle is comparatively similar, partly because the number of pins is different, the switch is different, so leading to its most fundamental working principle has certain differences. What is the working principle of the four foot light touch switch?
Working principle of four foot light touch switch
First, it is composed of normal open contacts and normal closed contacts. In the light touch switch, the function of normal open contacts is that when the pressure is applied to the normal open contacts, the circuit will turn on; when the pressure is removed, it will return to the original normal closed contacts, that is, the so-called disconnection. The pressure is to use our hands to open the button and turn the button.
2. When the pressure is withdrawn, the four-legged light touch switch will be closed. The internal structure of the four-legged light touch switch relies on the metal shrapnel to protect the force situation and realize the connection and disconnection.
The principle of four-legged light-touch switch is related to its structure, such as 220V AC through the bulb H and rectifier bridge, into a DC pulsating voltage as a forward bias, added to the thyristor VS and R branch.
1. In the daytime, when the brightness is greater than a certain degree, the photodiode D presents a state of bottom resistance <1K, so that the transistor V cuts off, the emitter has no current output, and the unidirectional 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 can not emit light. The resistance R1 and the voltage regulator diode DW make the bias voltage of the transistor V not exceed 6.8V, and protect the triode.
2. At night, when the brightness is less than a certain degree, the photodiode D presents a high resistance state (> 100K), making the transistor V forward conduction, the emitter has a voltage of about 0.8V, so that the thyristor VS triggers conduction, and the bulb H emits light. RP is the brightness selector for switching in the morning or evening.
Fourth, no matter what the structure of the light touch switch, the four-foot light touch switch has four pins in common. The advantage of the four-foot light touch switch over the ordinary light touch switch is that it can be soldered firmly. Everyone can use the four-foot light touch switch to adjust and control it accurately.