What Is a Pushbutton Switch?
A pushbutton switch is a switch that is turned on and off by a pushing motion with a human finger.
They are also called push-button switches. Pushbutton switches are used as human input devices for various controls. In many cases, their role is to directly turn on or off the electric current that operates the device.
There are a wide variety of shapes and sizes of actuators and mounting points. There is also a wide variety of colors when issued, with or without a light emission to indicate on/off.
Uses of Pushbutton Switches
Pushbutton switches are used in a variety of situations. Specifically, they are used as switches for operating control equipment and inputting setting conditions because they are input devices that are operated by human fingers.
Pushbutton switches are also used as input devices on operation panels of industrial machines to provide operation and stop instructions and input settings for various operating conditions. In addition, they are also useful for devices that generally use human operation as input for operation settings and turning on/off of operations, such as power on/off operations for household electrical appliances.
Principle of Pushbutton Switches
The typical construction of a pushbutton switch is one in which the connecting terminal of the switch is connected to a pushbutton and the contacts make contact when the button is pressed. Conversely, there is another type in which the connecting terminal is pressed against a spring and the contact is separated when the button is pressed.
Some switches have a mechanical locking mechanism inside the switch that keeps it in operation when pressed once. When it is time to put it back on, there are various types, such as push again, pull back, and twist types.
One of the features of pushbutton switches is that many types of illuminated switches use light to indicate whether the switch is on or off. Illuminated switches have a light source such as LED inside.
Types of Pushbutton Switches
1. Momentary Type and Alternate Type
Pushbutton switches are divided into two types in terms of contact state switching: momentary type and alternate type.
The momentary type, as the name “momentary” implies, has an “instantaneous (temporary)” mode of operation. It turns on only while the switch is pressed.
The alternate type, meaning “alternating,” switches on when the switch is pressed and remains on when the finger is released. Then, when the switch is pressed again, it switches off and remains off when the finger is removed. Each time the switch is pressed, the operation alternates between on and off.
2. Latch Type and Unlatch Type
There are two types of push switches with different mechanical actions: latch type and unlatch type.
In the latch type, the switch is held in the depressed position once it is turned on by pressing it with a finger. Then, when the switch is pressed again, it returns to its original position and is turned off.
In contrast, the unlatch type returns to its original position once the switch is pressed, whether on or off.
How to Select Pushbutton Switches
1. Illuminated/Non-illuminated Type
Pushbutton switches are devices with high ergonomic requirements because they are pressed by human fingers. The illuminated type is useful for important actuators because it provides feedback to the operator on whether the switch has been turned on or off.
2. Surface Shape
The surface shape of a switch is considered to be concave for better operability. On the other hand, flat type is easier to indicate letters and symbols.
3. Method of Operation
Select a method of operation (momentary/alternating, latching/unlatching) that is suitable for the intended use. It is also desirable to check that the force required for operation is not too large or too small and that the latch has an appropriate feel.
4. Environmental Resistance
Consideration should be given to dustproofness and waterproofness according to the environment of use. The IEC (International Electrotechnical Commission) has established an IP code as a standard for dustproof and waterproof switches.
The first number indicates dustproofness, and the second number indicates waterproofness. The higher the number, the higher the performance. Some products have a rubber “waterproof cap” covering the important parts of the product to simplify dustproof and waterproof performance.
5. Rated Current/Voltage
Since most pushbutton switches are used to open and close an electric current, it is important to know how much current and voltage they can be used up to. The guideline for this is the “rating,” which is indicated in terms of DC or AC, rated voltage, and rated current. Select a switch with a sufficient margin for the actual operating conditions.