Introduction to the principle, difference, life and wiring methods of tact switches

Before understanding the difference between a tact switch and a key switch and the wiring method of the tact switch, we must first understand the principle of the tact switch .

Only after the user knows the principle of the tact switch, can it be used in the right place correctly. According to different principles, tact switches can be divided into two types: one is to use metal shrapnel to complete the switching of the on-off state of the switch; the other is to use conductive rubber to complete the switching of the on-off state of the switch. The structure of the tact switch, from top to bottom, is composed of: an insert, a base, a shrapnel, a button, a cover, and a pin . The waterproof tact switch is composed of a layer of polyimide film on the shrapnel.


Among them, the button is the place where the external force is applied through the cover plate; the shrapnel is the core component of the tact switch; the pin refers to the connection between the tact switch and the circuit. Generally, there are five pins, two pins are a group, and the fifth pin acts as a ground. When an external force is applied to the switch, the four pins are turned on, so that the switch is turned on; when there is no external force, the four pins are connected. The two groups are not connected, and the switch is in the off state. The on-off of the tact switch is realized by the change of the force of the metal shrapnel. When the switch button is pressed, the shrapnel is deformed by the external force and contacts the solder pad downward, so that the two sets of pins of the switch are connected to each other, so that the The circuit is in a conducting state. When the external force is withdrawn, the deformation of the shrapnel returns to the original state, and the two sets of pins of the switch are no longer connected, and the circuit is in a disconnected state.

So people often confuse tact switches and key switches, and people often say that tact switches are key switches. So, what is the difference between them?

The tact switch is a point-and-click switch, that is to say, press it to turn on and release it, and then disconnect it.
The key switch refers to the key switch that is pressed to connect. In fact, some people also call the touch switch also called the key switch. The key switch usually means that

the switch with a larger stroke can be self-locking. and lock-free. Highlight the action force of a press. A light touch is a short stroke and a short touch. Means a touch.
Then there is a more concerned topic like this, what is the lifespan of the tact switch ?


Any item has a fixed usage time, which varies in length. Of course, the same is true of the tact switch. Since it is often touched by people, the user needs to know the lifespan of the tact switch, so as to facilitate the replacement work in advance. For the life test of the tact switch, the number of times it is opened and closed is mainly tested until it is damaged. If you don't need to do it manually, you can use a small motor to drive the eccentric opening and closing switch, and use a counter to record the number of times. Domestic shrapnel life: 50,000-70,000 times; imported shrapnel single-sided double silver life: more than 100,000 times; stainless steel shrapnel more than 500,000 times high life. The body of the tact switch is composed of a plastic base. Its plastic base is composed of three materials: PA66, POM, and LCP, and the precision of the material is relatively high. The most important thing is that it feels very good. Tact switches of different materials have different shelf lives. The shelf life of these three materials is different. Generally speaking, the shelf life is about 10 years, and some may even be longer. Within 10 years, there will be basically no aging, but if it exceeds ten years, it is uncertain. In short, the lifespan of different types of tact switches is completely different. For example, waterproof and ultra-thin tact switches will have a longer service life. This kind of switch uses plastic material and has a shelf life of about 10 years.

Finally, it is about the introduction of the tact switch wiring method , so how to connect the four feet of the tact switch?


The four-foot tact switch cannot be self-locked during use, but as long as the user presses it once, the signal of the four-corner switch will change once. As for how to connect the four corners of the tact switch, this is very important knowledge for electricians, as follows:
1Adjust the multimeter to the diode;
2First measure any two feet in the four corners to determine which two corners are connected and which two corners are disconnected;
3Press the button, and then measure any two feet, and then judge which two corners are connected and which two corners are disconnected;
4Start to disconnect, press the button to turn on the two feet can be used as the two corners of welding.


According to the experience of professionals, direct welding is generally possible as long as it is diagonal.
It should be noted that the working principle of the key switch is that when the button is pressed, the two patches are close, that is, they are turned on; when they are released, the patches are separated, that is, disconnected.

In fact, the working principle of the four-foot tact switch is similar to that of the ordinary button switch, which is composed of normally open contacts and normally closed contacts. In the four-pin key switch, the function of the normally open contact is that when the pressure is applied to the normally open contact, the circuit is turned on; when the pressure is removed, the original normally closed contact is restored. Also known as disconnection. This pressing force is the action of using our hands to turn the button on and off.