Limit Switch Explained- Its Meaning, Components and Working Principles

Limit switches are electromechanical devices that are operated by an external physical force, usually applied to it by an object. These switches are used to detect an object’s absence or presence, usually in industries.

Limit Switches are made up of an actuator that is connected to a series of contacts. On the basis of detection by contacts, the sensor usually moves an actuator, which changes the electric circuit’s state. And what does this movement signals? It shows that the pre-set limit is reached.

As these limit switches detect the pre-set limits automatically, it eliminates the requirement for human workers to monitor the levels. And this convenience makes the operating of machinery and devices from industrial conveyor belts to heavy machinery easier, precise, and reliable.  And, as a result, the work environment becomes safer and efficient.

Components Of Limit Switches

1. Actuator/Operating Head

The actuator is a part of limit switches that physically comes in the target’s contact. However, in some limit switches, an actuator is attached or connected to the operating head that translates a linear, perpendicular or rotary motion to close or open switches’ electrical contacts.

2. Switch Body

The component that contains the mechanism of electrical contact.

3. Receptacle/Terminals

The component that contains the screw/clamp assembly or terminal screws, required for wiring purposes.

Benefits And Features of Limit Switches

Limit switches can be used in most of industrial environments. Find below a few benefits and features of limit switches.

1. They are precise in terms of repeatability and accuracy
2. They use electrical energy efficiently
3. They can easily switch high inductance loads
4. They can control multiple loads

Uses of Limit Switches

Limit switches are used to tally material or items, such that when the pre-set limit is reached, the switch automatically opens or closes. And, this condition is commonly observed in industrial applications, like assembly lines. For say, a limit switch is present in a piece of equipment and detects that it has added a predetermined count of components in a product, in this case, the limit switch moves the actuator, this moves the equipment’s piece away, and the product simply goes to the next station.

The limit switches can be used as safety interlocks as well for preventing machine parts from moving further whenever it reaches a specific point. An appropriate example to mention here would be that of an automatic garage door. In this, the limit switch stops the door after it reaches a certain point or bottom rail. Otherwise, the door might keep moving downwards and crash into the ground, resulting in serious damage.

Limit switches can also be a part of large control systems. And, when a certain limit or maybe pre-set limit is reached, the actuator can activate or de-activate a device, preventing emergencies or malfunctioning.

Another use of limit switches is that you can use button actuators in place of a rotating arm. Suppose you have a dump truck, and you want to ensure that, before the truck drives away, the bed should be in a down position. Here, you can use a button actuator with a position limit switch so that, when the bed is fully down, the button actuator is pressed in. And, when the button is pressed, the limit switch closes, indicating the driver (with the help of light or alarm) that the bed is down and they can drive safely.

As there are several types of limit switches available and all of them have different features, it is imperative to choose one that suits your applications and uses. However, as it might involve technicalities, it is advisable to consult an expert professional and seek advice to make an appropriate choice.