What are the push button switches commonly used by electricians?

Push button switch function

A push button switch is a control switch that uses a certain part of the human body (usually a finger or palm) to apply force and has a spring stored energy to reset. It is the most commonly used master electrical appliance. The allowable current through the contact of the push button switch is small, generally not more than 5A. Therefore, under normal circumstances, it does not directly control the on and off of the main circuit (high current circuit), but sends command signals in the control circuit (small current circuit) to control electrical appliances such as contactors and relays, and then they control the main circuit On-off, function conversion or electrical interlocking.

Siemens APT Push button switches

The structure principle and symbol of the push button switch

The push button switch generally consists of a button cap, a return spring, a bridge-type moving contact, a static contact, a pillar connecting rod and a shell.

The opening and closing state of the contact when the push button switch is not subjected to external force (ie, static), divided into stop push button switch, start push button switch and compound push button switch.

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

Meaning of push button switch color

Push button switch color	Meaning	Description	Application example
Red	Urgent	Operation in danger or emergency	Emergency stop
Yellow	Abnormal	Operate in abnormal situations	Intervention to stop abnormal situations
Green	Normal	Start operation under normal conditions
Blue	Mandatory	Operation when forced action is required	Reset function
White	No specific meaning	Start of general functions except emergency stop	Start/on (priority), stop/off
Gray			Start/on, stop/off
Black			Start/on, stop/off (priority)

Push button switch structure code

K—open type, embedded in the operation panel;

H—protective type, with protective shell, which can prevent internal parts from being damaged by machinery or accidentally touching live parts;

Push button switch model and meaning

S—Waterproof type, with a sealed shell to prevent rainwater from intruding;

F—anti-corrosion type, can prevent corrosive gas from entering;

J—emergency type, with a big red mushroom push button switch (protruding out), used for emergency power off;

X-knob type, use the knob to rotate for operation, there are two positions of on and off;

Y-Key operation type, use the key to insert for operation, which can prevent misoperation or be operated by special personnel;

D—cursor push button switch, the push button switch is equipped with a signal lamp, which also serves as a signal indicator.

Selection of push button switchs

1. Select the type of push button switch according to the use occasion and specific purpose. For example, the push button switch embedded in the operation panel can be an open type; the cursor type that needs to display the working status; the key-operated type should be used for important occasions that need to prevent personnel from misoperation; and the anti-corrosion type should be used where there is corrosive gas.

2. Select the color of the push button switch according to the working status indication and working condition requirements. For example, the start button can be white, gray or black, and white or green is preferred. The emergency stop button should be red. The stop button can be black, gray or white, preferably black, or red.

3. Select the number of push button switches according to the needs of the control loop. Such as single push button switch, double push button switch and triple push button switch.

Common faults and treatment methods of push button switchs

Fault phenomenon	Possible cause	Treatment method
Poor contact	The contact is burned out	Repair contacts or replace products
	The surface of the contact is dusty	Clean the contact surface
	Contact spring failure	Rewind the spring or replace the product
Short circuit between contacts	Plastic thermal deformation causes the terminal screws to touch and short circuit	Find out the cause of heat, troubleshoot and replace the product
Short circuit between contacts	Debris or oil forms a closed circuit between the contacts	Clean the inside of the button