In the vast majority of cases, a circuit must be capable of being switched on and off to be useful. According to ph-el.dk an uninterrupted flow of electricity through the various components is usually key to the functioning of a circuit. However, there are also times when the current must be arrested in order for a given system to function properly.
This is why switches were created.
Offered in a variety of different types, design concerns, functionality and aesthetic considerations can often combine to create situations in which the use of rotary, rocker, slide, or toggle switches are inappropriate. The purpose of push buttons in electrical systems then becomes apparent.
Advantages of Push Buttons
Typically requiring less space on a faceplate or a console, push-button switches are ideal when placement is a major concern. They can also be easier to use, as they require a simple touch rather than a range of movement.
Further, the potential for accidental engagement is reduced with push buttons. There’s less chance of inadvertently bumping into it and activating or deactivating the circuit. Push buttons must be definitively touched to function.
How Push Buttons Work
A common variety of switches employed on industrial control panels, most push buttons, like some of those offered by Schneider Electric, have internal spring mechanisms returning the buttons to their “out” or “unpressed” positions for momentary operation.
This spring contacts two wires, allowing electricity to flow when the switch is in the “on” position. The spring retracts; interrupting contact and breaking the circuit when the switch is in the “off” position.
Types of Push Button Switches
By and large, push button switches fall into one of the following categories.
• Normally-Off: The circuit is broken until the button is pressed. A good example of this a doorbell. Touching the button completes the circuit and causes the bell to ring. The ringer continues to function as long as you hold the button depressed and stops when you release it.
• Normally-On: The circuit is complete until the button is depressed, and interrupts the flow of electricity. In other words, pressing the button turns the device off.
• Non-Momentary Contact: Typically found on radios, television sets and audio amplifiers, these push buttons require a touch to close the circuit and another touch to open it. In other words, the device will continue to function once you press the button, until it is pressed again. In some instances, a non-momentary pushbutton will require the user to physically pull the button out to interrupt the circuit once it has been activated.
Push Button Categories
Separated into types, usually based upon the method by which they function, push button switches are categorized based upon the following attributes.
• Single-throw
• Double-throw
• Contact type
• Mounting type
• Actuator type
• Panel cutout diameter
Regarding the latter, the most commonly employed industrial size is 30 mm.
Push Button Ratings
Push button switches are also rated according to the current and voltage they are designed to manage. This is important to understand, as system designers must specify the appropriate component for everything to properly function.
You’ll need to specify larger, more expensive parts when you’re dealing with higher voltage and/or current requirements. However, it’s also important to ensure the switches employed are only as large as necessary to keep costs in line.
Simply put, the purpose of push button switches in electrical systems is to serve convenience, aesthetic, and safety needs. While their basic function is to close and/or open a circuit, push button switches also give designers a wider range of configuration options.
