Single position switches

Do you want to use single-position switches to control movements? Then use single position switches or limit switches. But what types of single-position switches are there and where are they best used? Find out here. Their functional principle is the same as with conventional switches, except that the switching process is automated or determined by external influences. Such an installation will help you avoid manual shifting where it is particularly difficult and/or dangerous.

Source: eibabo®, Schneider Electric XCKM115H29 position switch Image: Schneider Electric XCKM115H29 position switch

What are single position switches?

You won't use single-position switches that often in your home. Their areas of application are more in the industrial sector. There they ensure that a hydraulic, pneumatic, electrical or mechanical signal is triggered when a moving object has reached a specific position within a sequence control. This means, for example, that the position switch is activated or deactivated when the end of a specific production section has been reached and the next step in the process is to be started. Single position switches are also called limit switches, position switches or limit switches.

What types of single position switches are there?

Since the requirements in the industrial sector often depend on the respective process, the individual position switches can also be very different. A suitable solution is available for almost every application. In the following we will go into more detail about the functional principles and properties of the individual variants.

Mechanical single position switches

Single position mechanical switches can be found in both production and household settings. These switches often take the form of a button, roller, float, or lever. The classic example of the use of a mechanical single-position switch is the elevator. Only when the elevator car has reached a certain position can the door be opened. But these devices are also used in living areas in the form of microswitches. These can be found on front doors, for example, so that the lighting is switched on automatically when they are opened.

Single position switch with push button or wheel switch

These versions of the single position switches consist of a housing with electrical contacts that can either open or close. These are connected to a roller with a push button or a rod. The functional principle here is also a movement mechanism. For example, if the wheel collides with another object, it is pushed down by a rod. This opens or closes the contacts in the housing and triggers a follow-up action.

Assembly

When installing such a single-position switch, particular attention must be paid to accuracy. Otherwise, the movement of an object may not actuate the roller or push button properly, or, conversely, apply too much pressure.

This may then lead to faulty switching or damage to the mechanism.

micro switch

Single position switches as micro switches are used in electronics as well as in household appliances and are very small. Thus, these devices have special properties. Due to the compact dimensions, the stroke of the working part is small. As a result, installation often requires fine tuning or the use of an intermediate link. This makes it possible to increase the stroke of the working part to the extent required to ensure reliable switching.

Non-contact single position switches

This type of single position switch is widely used in industrial production. The market offers numerous variants as well as different functional principles and designs. The most important are:

reed switch

This type of limit switch reacts to a magnetic field. These devices consist of several pairs of ferromagnetic contacts. The contacts inside the reed switch close or open when a magnet approaches. Since no mechanical movements trigger the contact process, the service life of the switch increases significantly. A magnet must be present as a trigger during installation, as these devices do not react to other materials. The field of application of reed switches is very diverse. These often work as a microswitch variant, for example as an alarm switch on doors and gates. When the door is closed, the magnetic field acts on the reed switch and the circuit also remains closed. When the door is opened, the magnet moves away from the reed switch. The contact opens and the alarm is triggered.

Inductive switches

Inductive switches are suitable alternatives to mechanical types of position switches and work without direct contact. The devices work by means of an inductor, which reacts to metal. Compared to the reed switch, these switches do not require a magnet. Inductive models are used in security systems because they respond to both the weight of a metal and its movement. The advantage of inductive switches is their tolerance to environmental pollution. As a result, inductive switches are mainly used in technological processes of industrial production. The size can vary greatly depending on the place of use and function.

Switches with optical sensors

Switches with optical sensors are also non-contact single-position switches. Such devices are often used in areas where special accuracy is required. Optical position switches work according to several principles.

Reflective sensors send and receive light, which is reflected by an object located in the sensor area. Receiver and transmitter are in the same housing. The captured light energy causes a specific action at the output of the switch. The distance from the object to the sensor depends on its dimensions, texture, color and so on. If the light beam is crossed by another object and thus changes the captured light energy, a control signal is emitted. The range of such a position switch depends on the environment and its transparency.

With passage sensors, the receiver and light source are separate and face each other. An object entering the area of the light beam interrupts the light and thereby changes the light energy. Then a signal is triggered.

Capacitive position switches

The principle of operation of capacitive position switches is as follows: The active surface of the switch consists of two metal electrodes. These can be thought of as capacitor plates. If an AC voltage is applied to it, current flows. The strength of the current flow depends on the medium located between the plates, the distance between the plates and the plate size.

TIP

Capacitive switches detect conductive and non-conductive materials in liquid, powder, or solid states.

When an object appears near the active surface, the strength of the current flow changes. The position switch reacts to this and triggers an action.

Are there also wireless single-position switches?

Wireless instead of cable – the wireless position switch offers you additional flexibility when designing machines and systems. You can mount these switches on fixed and moving components without a great deal of assembly work, without having to lay cables or ensure that the cables are laid without any problems. Depending on the manufacturer, the devices offer different transmission protocols or the option of integration into different wireless networks. The differences lie in the range and transmission security, among other things. In addition, there are models with or without feedback (monodirectional or bidirectional).

With the single position switches from the eibabo® online shop, you can automate your production processes and thereby improve your efficiency. Since these switches are intended for industrial use, they are very robust, protected from dust and water and are particularly reliable. Manufacturers of high-quality single-position switches are ABB, Eaton, Honeywell, Omron, Rockwell, Schneider Electric, Siemens, Stahl, Steute and others.