Switches and push buttons

An introduction

1. Introduction

What do switches and push buttons do?

The purpose of a switch/button is to establish an electrical connection that can be disconnected again. Switches and push-buttons are activated to enable a controlled flow of electricity. In addition to the term “switch”, the name “changeover / toggle switch” is also commonly used; both terms can be used interchangeably.

The concept of “circuit” in electrical engineering is based on the same principles. We are dealing with circuits that are comparable on both a small and large scale. The light switch on the wall works as a circuit in the same way as the gear shift in a vehicle, even if the individual elements and their surroundings have little in common at first glance.

What does this info article offer?

This article takes a look at switches and push buttons and explains their differences. The large group of switches and push buttons can be classified according to type. The first and simplest distinguishing feature concerns the type: Is it a mechanical or electronic switch / push button? We then classify switches and buttons, provide examples of applications and show some examples of Delock products in this area. - In the following, we use the term “switch” to also mean “push button”.

2. Types and subtypes of switches

Type: mechanical or electronic?

Mechanical switches isolate galvanically and thus completely. There is no electrically conductive connection when the switch is open. With electronic switches, there is no galvanic isolation. Such a switch is a semiconductor element. It reduces or blocks the current flow. It does not disconnect mechanically and the conductive connection is never completely interrupted.

Typing of switches

Depending on how a switch behaves when actuated, its basic function can be classified. The basic functions allow further classification, which are then variants of the basic function. The technical terms for switches refer to the basic functions and the mechanisms on which they are based. There are differences between:

A.: NO contact, NC contact or changeover contact switch?

A normally open contact must be actuated to establish the electrical connection. The connection is open when it is not actuated; no current flows. A normally open contact is also referred to as NO: this stands for “normally open”. - The opposite is true for a normally closed contact: when it is at rest, it is closed and current flows. When actuated, the electrical connection is disconnected. A normally closed contact is also referred to as NC, which stands for “normally close”.

When a changeover contact is actuated, the connection switches to another contact. If a changeover contact is actuated again, it switches back to the original contact. In the case of a changeover contact with a momentary connection, the switchover takes place when the actuation is ended. In simple terms: when the pressure from the finger is no longer applied, the button returns to its original position, see also below.

B.: Latching or momentary-action switch?

A latching switch maintains its new position independently after it has been actuated: it is then latched. A momentary-action switch, on the other hand, has a rest position which it returns to after the end of actuation - it returns to the rest position. - A practical example of how to use the previous type and classification: The Delock push button Item 20979 is an electronic push button of the changeover contact type, designed as a push button.

C.: Single-pole or multi-pole switch?

There are single-pole and multi-pole switches, depending on how many separate electrical connections can be connected to each other. The single-pole switch connects one connection to another. The two-pole switch connects two connections to two others, and so on.

D.: Bridging or non-bridging switch?

With a bridging switch, all connections are connected to each other at the moment of switching. There is a “bridge” of electrical voltage. This is because the bridging switch first connects to terminal 2 before it disconnects the contact to terminal 1. With a non-bridging changeover switch, the contacts are open at the moment of switching: Connection 1 is disconnected before being connected to connection 2. The advantage of this design is that it can prevent a short circuit in the supply voltage. Accordingly, this type is more common.

3. Switches in application - practical examples

Toggle switches are one of the most commonly used types of switch. They are used in homes, for example, and are used to switch lamps on and off. They are usually fitted with a plastic cover that protects and conceals the electronics behind them.

Pressure switches work by changing the pressure of media such as air. As soon as the pressure on the switch varies, a circuit is either closed or opened. This technology enables precise control by changing the pressure.

A latching switch, similar to other types of switches, is activated by pressure. As soon as it is pressed, it mechanically engages in a position and closes the circuit. When pressed again, the latching mechanism releases, interrupting the circuit. Such switches are often used in machines as “emergency switches” to ensure the safety of the operator.

The rotary switch differs from conventional switches in the way it works. As the name suggests, it is activated by a rotary movement. This establishes the contacts to the conductive connection. To break the circuit, the switch is turned back to its original position. These switches are often found in cameras.

The step switch, also known as a rotary switch or flat track switch, offers several switching positions. It connects different connections to each other, allowing the desired level to be selected. This type of switch is often used to control signals or to regulate voltage.

Bell push buttons are among the best-known push-button switches. When the button is pressed, a connection is created that triggers an acoustic signal - such as the ringing of a doorbell or the honking of a vehicle horn.

Most people are familiar with the eject button from cars or electronic devices. It is used on radios or DVD players, for example. Pressing the button triggers the ejection of the medium so that it can be conveniently removed.

Signal buttons are often found in telephones. They enable a signal to be forwarded for an incoming call. An acoustic signal is generated by connecting the lines together.

4. Product examples for installation by Delock

These push buttons by Delock are ideal for installation in control panels, for example in industry, control or regulation technology, in the automotive sector or for various applications in the end customer sector. All the products shown here have following specifications in common:

Item 20982
Push Button 12 mm - LED green dot

• 4 x solder connection
• Switch type: 1NO + 1NC
• Mounting depth: ca. 18 mm
• Thread size: M12
• Dimensions (LxD): ca. 23 x 14 mm

Item 20980
Push Button 19 mm - LED blue

• 4 x screw terminal
• Switch type: 1NO + 1NC
• Mounting depth: ca. 28 mm
• Thread size: M19
• Dimensions (LxD): ca. 30 x 25 mm

Item 22051
Push Switch 22 mm - LED white power symbol + ring

• 6 x solder connection
• Switch type: 2 NO + 2 NC
• Mounting depth: ca. 39 mm
• Thread size: M22
• Dimensions (LxD): ca. 40 x 30 mm

Item 20987
Push Switch 25 mm - LED red power symbol + ring

• 6 x solder connection
• Switch type: 2 NO + 2 NC
• Mounting depth: ca. 39 mm
• Thread size: M25
• Dimensions (LxD): ca. 45 x 30 mm

The product range of push buttons / switches at Delock is just being established (status: December 2024) and will be expanded in the future. An overview of all available items:

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