What Is a Pushbutton Switch?
A pushbutton switch is a switch that opens and closes electrical contacts by human operation.
It refers to a component whose contacts are changed to open or close when a person pushes it in with a finger.
Uses of Pushbutton Switches
Pushbutton switches are used in a wide range of applications, from daily necessities to industrial machinery, and are often seen in our daily lives. Specific uses of pushbutton switches are as follows:
- Game machine controllers
- Pump operation switch for drainage
- Operation/stop switch of water heater
- Various buttons on TV remote controls
Principle of Pushbutton Switches
Pushbutton switches consist of a button, case, and contacts.
1. Button
The button is the part that a person pushes in. Generally, colored resin materials are used to insulate the button from the electric circuit and to color-code the function of the button.
2. Case
The case is the exterior part that holds the pushbutton and electrical circuits. It supports the internal mechanism while protecting it from the outside and prevents people from easily touching the electric circuits. Therefore, it is composed of insulating materials such as resin or rubber.
3. Contact Point
The contact is the part that converts the operation on the pushbutton into an electrical contact. It consists of a spring and a piece of metal. The spring restrains the button to return to its original position after being pushed. The metal strip consists of a fixed contact and a movable contact, etc., and conducts or breaks the electrical signal.
Types of Pushbutton Switches
There are two functional classifications of pushbutton switches: alternate and momentary.
The former is a switch that is activated only while the button is depressed and simultaneously deactivated the moment the finger is released. The latter is a switch that is activated when the button is pushed buttoned and continues to be activated thereafter until the button is pushed again.
1. Alternate Type
In pushbutton switches, alternating refers to a switch that alternates states each time it is pressed. Buttons for function selection, for example, should be of the alternate type because they should retain their state. The main power supply of a monitor or the power supply of a flashlight are examples.
2. Momentary Type
In pushbutton switches, momentary refers to a switch that is activated only while it is pressed. It is used when you want to make a delicate action, or when you want to press it only once for a single action. A video game controller is an example.
Various other types are also available and are selected according to the specifications of the equipment. In places where people frequently pass by, covered or guarded switches are often used to prevent accidental operation.
Pushbutton switches with lamps are also available, and the lamps can be lit by supplying power. They are called illuminated pushbutton switches. The “ON” and “OFF” states are indicated by the illumination of a lamp.
Other Information on Pushbutton Switches
1. How to Wire a Pushbutton Switch
Various types of wiring methods for pushbutton switches are sold by various manufacturers, but the most common types are soldering, screw terminals, and spring terminals. The soldering type connects the wiring to the terminals with solder. Generally, the connection part and the button part can be split, and only the button part can be replaced.
In the screw terminal type, the wiring is crimped to a crimp terminal such as a Y terminal or a round terminal, and fixed to the connection part of the pushbutton switch with a screw. The spring terminal type is fixed by clamping the wiring with a spring. Crimp terminals are not necessary and wiring work can be easily performed. However, there are cases where a rod terminal is used for the terminal section.
2. Contacts of a Pushbutton Switch
Pushbutton switches have three types of contacts: A, B, and C. The A-contact is the one that conducts when the button is pushed in. The A-contact is the contact that conducts when the button is pressed in. Normally, the switch is open and no current flows through the circuit. It is also called a normally open (NO) contact, meaning that it is normally released.
The B contact is the contact that opens when the button is pushed in. In normal operation, the switch is in a conducting state and current flows through the open circuit. It is also called a normally closed (NC) contact. (NC) Also called a contact.
A c-contact is a three-terminal contact that combines an A-contact and a B-contact. A-terminal, B-terminal, and A-common terminal. In normal operation, the A-terminal is open and the B and common terminals are conducting. When the switch is pushed in, the A-terminal and the common terminal conduct and the B terminal is open.