There are two functions of touch switch: one is normally open, the other is normally closed. The most common type is normally open type. Normally open type refers to that the line is generally disconnected. Gently press the handle of the key to touch the bullet and the shot point of the base. At this time, the switch is regarded as on. Release the handle of the key to separate the bullet and the shot point. At this time, the switch is regarded as separate. The performance of the product is OK. When the line is disconnected, the resistance of the two circuits is 30 m Ω. When the switch is on, the contact resistance of the two circuits is 0. At this time, the switch performance is very good. Normally closed type is relatively rare, because it does not conform to the conventional product design. Normally closed type means that the switch is on normally, and when the switch is touched, the circuit and function are off. The resistance of the switch is opposite to that of the normally open switch, so it is not recommended. The figure below shows the normally open tap switch

 

Whether it is normally open or normally closed, the touch switch must be composed of more than two pins, so as to form a group of switch functions, which are normally two pins, four pins and five pins. Why is there a five pin switch? Because the fifth foot is used for grounding, I think everyone knows what the grounding foot is used for. Of course, there are three feet. Generally, there are more side pressure on the three feet. This third foot is designed for fixation, so you can rest assured to use it. It's no problem to press hard. In the figure below, we can see the two pin circuit at a glance. Let me explain how to connect the four pins of the tap switch! Normally, 1 and 2 are a group of conduction, 3 and 4 are a group of conduction. When the switch is touched, 1 and 3 are a group, 2 and 4 are a group. It is right to design the function of the switch in this way.