Button switch
Button switch, also called control button (button for short), is a kind of low-voltage electrical appliance that can be reset manually and generally automatically. Button switch is usually used to send start or stop commands in the circuit to control the connection and disconnection of coil current of electromagnetic starter, contactor, relay and other electrical appliances. Push button switch is an electrical appliance that can be used to connect and disconnect small current circuits when pressed and reset when released. It is generally used in the control circuit with AC and DC voltage below 440V and current less than 5A. Generally, it does not directly operate the main circuit, but also can be used in the interconnection circuit. In actual use, in order to prevent misoperation, button switches are usually marked or painted with different colors, including red, yellow, blue, white, black, green, etc. Generally, red indicates operation under "stop" or "dangerous" conditions; Green indicates "Start" or "On". The emergency stop button must be a red mushroom button. The button switch must be equipped with a metal protective retaining ring, and the retaining ring must be higher than the button cap to prevent accidental touch of the button and misoperation. The material of button board and button box for installing buttons must be metal and connected to the main grounding bus of the machine. Selection of button switch: (1) According to the different use occasions and specific purposes: select the type of button according to the use occasions, such as open type, protective type, waterproof type, anti-corrosion type, etc; Appropriate forms shall be selected according to the use, such as handle rotary type, key type, emergency type, light type, etc. For example, the open button switch can be used first for the general buttons on the panel of the console cabinet; If it is necessary to display the working status, use the type with indicator light; In very important places, the key type button switch should be selected to prevent irrelevant personnel from misoperation; Anticorrosive type shall be used where there is corrosive gas. (2) Select the color of buttons and indicators according to the requirements of working status, instructions and working conditions: green for "start" or "power on", and red for "stop". In addition, the voltage (bulb) of indicator light is divided into 6.3V, 12V, 24V, etc. (3) Press the control circuit to determine the number of different buttons: such as single button, double button, three buttons, multiple buttons, etc. For example, three buttons can be used and installed in the same button box when three controls of "positive", "negative" and "stop" are required; When only "start" and "stop" control is required, two button switches are assembled in the same button box. Working principle of button switch: when the button is not pressed, the moving contact is connected with the static contact above, and this pair of contacts is called normally closed contact. At this time, the moving contact is disconnected from the static contact below, and this pair of contacts is called normally open contact: press the button, the normally closed contact is disconnected, and the normally open contact is closed; Release the button to restore the original working state under the action of the return spring.