Components of key switches and electrical precautions

Composition of a pushbutton switch.

1. Installation part: used to fix the button;

2. Operation part: transfer the external operating force and stroke to the switch part;

3. Shell part: electrically insulated and protects the internal component part;

4. Switch part: connect or disconnect the line;

Precautions. Regarding the load to be used: There is a big difference in switching capacity in AC and DC circuits, please confirm the rated value, please use it within the allowable inrush current value;

About the connection of the load: Please do not connect the power supply of different poles and different types on the contact of one switch;

About the use environment: avoid use in high temperature, high humidity, corrosion, high dust and other environments;

About switches: Never use loads that exceed the opening and closing capacity ratings of switches.

The constituent elements of a key switch.

The so-called key switch is an operating switch that presses or pulls out the switch contact by hand along the direction of the operating part along its axis.

The operation section is functionally divided into a type with a light and a type without a lamp.

The illuminated key switch is roughly composed of five parts. (1 button cap, 2-lamp, 3-moving contact, 4-normally open static contact, 5-normally closed static contact).

The unlit key switch consists of four parts after the light source is removed.

Electrical considerations for key switches.

1.About using loads.

There is a big difference in switching capacity between AC and DC circuits, so please check the rating.

In the case of DC, the control capacity is very low. This is mainly because DC does not have a zero point (zero crossing point of current) like AC, so once an arc is generated, it is difficult to eliminate it, and the arc time is very long. In addition, the direction of the current does not change, so there will be a phenomenon of contact migration, and the contact will not be able to be disconnected due to unevenness, which may lead to malfunction.

There are some types of loads where the constant current and the inrush current vary greatly. Please use within the allowable inrush current value. The larger the inrush current in a closed circuit, the greater the consumption and migration of the contact, and the failure of the contact to switch due to the fusion and migration of the contact.

In the case of induction, a reverse induced voltage is generated, and the higher the voltage, the greater the energy, and the higher the contact consumption, the higher the migration of the contact, so please check the rated conditions.

1. The emergency button switch is a switch that is touched when you need help in an emergency. It is the main switch used to control the 2 secondary lines.

2. Button is a commonly used control electrical component, which is commonly used to turn on or off the 'control circuit' (in which the current is very small), so as to achieve the purpose of controlling the operation of the motor or other electrical equipment. Common buttons are mainly used as emergency stop buttons, start buttons, stop buttons, combination buttons (keyboards), jog buttons, and reset buttons.

<>First, the function of the button

The button is a kind of control switch that is operated by exerting force on a certain part of the human body (generally fingers or palms) and has a spring energy storage reset, and is one of the most commonly used main electrical appliances. The contact of the button allows a small amount of current to pass through, generally not more than 5A. Therefore, under normal circumstances, it does not directly control the on/off of the main circuit (high-current circuit), but sends out command signals in the control circuit (low-current circuit) to control contactors, relays and other electrical appliances, and then they control the on/off of the main circuit, function conversion or electrical interlocking.

Second, the structural principle and symbol of the button

The button is generally composed of a button cap, a return spring, a bridge moving contact, a static contact, a strut connecting rod and a shell.

When the button is not affected by external force (i.e., static), the contact state is divided into stop button (i.e., dynamic button), start button (i.e., dynamic button) and composite button (i.e., dynamic and closed contact combination button).

When the button is subjected to external force, the opening and closing state of the contact changes

3. The meaning of the color of the button

Fourth, the model and meaning of the button

Fifth, the button structure form code

k—open type, inlaid on the operation panel;

h—Protective type, with a protective shell, which can prevent the internal parts from being damaged by machinery or accidentally touching the live part;

Sixth, the type and meaning of the button

s—waterproof type, with a sealed shell, which can prevent rainwater ingress;

f—anti-corrosion type, which can prevent corrosive gases from entering;

J - emergency type, with a red big mushroom button (protruding outside), for emergency power cut-off;

X—knob type, operate with knob rotation, with two positions: on and off;

y—key-operated, operated with key insertion, which can prevent misoperation or be operated by a special person;

d—cursor button, the button is equipped with a signal light, which doubles as a signal indication.

7. The selection of buttons

1. Select the type of button according to the use occasion and specific purpose. For example, the buttons embedded in the operation panel can be open; The cursor type that needs to be displayed to display the working status is selected; For important occasions where it is necessary to prevent personnel from misoperation, it is advisable to use the key operation type; In the place of corrosive gas, the anti-corrosion type should be used.

2. Select the color of the button according to the working status indication and the requirements of the working situation. For example, the start button can be white, gray or black, and white can be preferred or green. The E-STOP button should be red.

The stop button can be black, gray or white, with black or red preferred.

3. Select the number of buttons according to the needs of the control loop. Such as single-button button, double-button and triple button and so on.

Please refer to page 21 of the standard friendly photo "Common Graphics and Text Symbols for Building Electrical Engineering Design" 09DX001.

There are many types of structure of push button switches, which can be divided into ordinary button type, mushroom head type, self-locking type, self-centering type, rotary handle type, indicator type, light symbol type and key type, etc., there are single buttons, double buttons, three buttons and different combination forms, generally using building block structure, composed of button caps, return springs, bridge contacts and shells, etc., usually made into a wide and wide composite type, there is a pair of normally closed contacts and normally open contacts, and some products can increase the number of contacts through the series connection of multiple components. There is also a self-holding button that automatically holds the closed position when pressed and can only be opened when the power is off.

Pushbutton switches can complete basic controls such as starting, stopping, forward and reverse, changing speeds, and interlocking. Usually each pushbutton switch has two pairs of contacts. Each pair of contacts consists of one normally open contact and one normally closed contact.

When the button is pressed, the two pairs of contacts act at the same time, the normally closed contacts are disconnected, and the normally open contacts are closed.

In home decoration, I believe that everyone is no stranger to button switches, but if you really want to say why the button switch comes out, you can't say it for a while, the button switch refers to the use of buttons to push the transmission mechanism, so that the moving contact and the static contact are on or off and realize the circuit replacement switch. There are many types of button switches on the market, and today the home improvement network will explain the structural characteristics of the switch button types in detail, let's take a look.

Button switch refers to the switch that uses the button to push the transmission mechanism, so that the moving contact and the static contact are connected or disconnected and realize the replacement of the portable circuit

1. Normally closed button.

2. Normally open button.

3. Composite button.

Button switches can be classified according to the mode of operation and protection, and the common button categories and characteristics:

1. Waterproof: The shell with sealing can prevent rainwater from invading. The code name is S.

2. Anti-corrosion type: it can prevent the intrusion of chemical corrosive gases. The code name is F.

3. Explosion-proof type: It can be used in places containing ** gases and dust without causing explosion, such as coal mines and other places. The code name is B.

4. Knob type: rotate the operation contact with the handlebar, with two positions of on/off, generally panel mounting. The code name is X.

5. Key type: use the key to insert and rotate for operation, which can prevent misoperation or be operated by special personnel. The code name is Y.

6. Open type: suitable for embedding and fixing Paga on the panel of the switch board, control cabinet or console. The code name is K.

7. Protective type: with a protective shell, it can prevent the internal button parts from being damaged by machinery or touching the belt.

The electrical part, codenamed H.

8. Emergency type: there is a big red mushroom button protruding outside, which is used to cut off the power supply in case of emergency. The code name is J or M.

9. Self-holding button: The button is equipped with a self-sustaining electromagnetic mechanism, which is mainly used in power plants, substations or test equipment, where operators communicate signals and issue instructions, etc., generally for panel operation. The code name is Z.

10. Button with light: The button is equipped with a signal lamp, which is used as a signal indication in addition to issuing operation commands, and is mostly used on the panel of the control cabinet and console. The code name is D.

Combined: Multiple button combinations. The code name is E.

Interlocking: Multiple contacts are interlocked with each other. The code name is C.