The four pins of the key switch are normally open and normally closed, and which two are used depends on the requirements of the circuit. initiate. When the button is not pressed, it is called normally closed, and when the button is pressed, it is disconnected. When the button is not pressed, it is called normally open, and when the button is pressed, it is connected. Of course, it is measured by the ohm gear (Ω) of the multimeter.
There are many structural varieties of key switches, which can be divided into ordinary button type, mushroom head type, self-locking type, self-resetting type, rotary handle type, indicator type, lamp symbol type and key type, etc. Buttons, three buttons and different combinations are generally made of building blocks, which are composed of key caps, reset springs, bridge contacts and shells, etc., generally made of composite type, with a pair of normally closed contacts and normally open contacts. Some products can increase the number of contact pairs by connecting multiple components in series. There is also a self-restraint button, which can automatically maintain the closed position after being pressed, and can be opened only after the power is turned off.
The key switch can complete basic control such as start, stop, forward rotation, speed change and interlock. Generally, each key switch has two pairs of contacts. Each pair of contacts consists of a normally open contact and a normally closed contact. When the button is pressed, the two pairs of contacts act together, the normally closed contact is disconnected, and the normally open contact is closed.
(1) Open type: It is suitable for flushing and fixing on the panel of switch board, control cabinet or console. Codenamed K.
(2) Protection type: with a protective shell, which can prevent the internal button parts from being mechanically damaged or people touching the live parts, the code is H.
(3) Waterproof: With a sealed case to prevent rainwater intrusion. Codenamed S.
(4) Anti-corrosion type: It can prevent the intrusion of chemical corrosive gases. Codenamed F.
(5) Explosion-proof: It can be used in places containing explosive gas and dust without causing explosion, such as coal mines and other places. Codenamed B.
(6) Knob type: the handle is rotated to operate the contact, there are two positions on and off, and it is generally panel-mounted. Codenamed X.
(7) Key type: use the key to insert and rotate for operation, which can prevent misoperation or be operated by special personnel. Codenamed Y.
(8) Emergency type: there is a big red mushroom button protruding outside, which is used to cut off the power in an emergency. Codenamed J or M.
(9) Self-sustaining button: The button is equipped with a self-sustaining electromagnetic mechanism, which is mainly used in power plants, substations or test equipment. Codenamed Z.
(10) Illuminated button: The button is equipped with a signal light, which is used for issuing operation commands and also serves as a signal indication, and is mostly used on the panels of control cabinets and consoles. Codenamed D.
(11) Combination: Multiple button combination. Codenamed E.
(12) Interlocking: Multiple contacts are interlocked with each other. Codenamed C.
Key Switch Applications
The key switch has the advantages of small contact resistance load, accurate operating force error, and diversified specifications. It has been widely used in electronic equipment and white goods, such as audio and video products, digital products, remote controls, communication products, and household appliances. , Security products, toys, computer products, fitness equipment, medical equipment, money detector pens, laser pen buttons and so on. Because of the environmental conditions of the key switch (elastic force with pressure less than 2 times/environmental temperature and humidity conditions and electrical performance), large equipment and high-load buttons are directly replaced by conductive rubber or dome switch hardware shrapnel, such as medical equipment, TV. machine remote control, etc.
