What is Limit Switch?

Limit switches are used to detect or feel the presence of an object or to monitor and signal whether the object’s movement restrictions have been exceeded. Limit switches were originally used to specify the limit or endpoint over which an item might travel before being halted, as their name implies. The switch to control the limit of travel was activated at this moment. We can control any electrical gadget with the help of a limit switch. A limit switch’s primary duty is to monitor and control the physical movement of any machine.

Parts of the limit switch

Parts of the limit switch are

  • Actuator
  • Head
  • Contact Block
  • Terminal structure
  • Body of the switch
  • Base


This is the section of the limit switch that would make contact with the object.


The actuator movement would be converted to contact movement in this section of the limit switch. So, if the actuator is properly moved, the switch contact will operate in accordance with it.

Contact Block

This portion of the limit switch would protect the switch’s electrical contact element. It usually has two or four contact pairs.

Terminal structure

This section contains the screw terminations and is where the switch and the rest of the control circuits make electrical connections.

Body of the switch

This limit switch component would include the contact and terminal block.


The terminal block in a plug-in switch would be housed in this area of the limit switch.

Working Principle of Limit switch:

The limit switch is activated by inserting the lever into the limit switch. When the device comes into contact with it, the lever turns. The micro switch inside the limit switch activates as it turns.

The limit switch’s tiny switch has a NO and an NC contact.

Difference between NO and NC Contacts

NC contacts:- This contact is de-energized, which indicates they are connected in the normal state. That is, if you use a Multimeter to examine the NC contact, you will find it in good condition.

NC contacts remain closed when not energised and open when activated.

NO contacts:- The same as NO (Normally open), these contacts stay open even when de-energized. That instance, if you use a Multimeter to examine the NO contact, you will notice that these two are far apart. NO contacts are normally open and close as soon as they are powered.

How does a limit switch operate?

This switch is electromechanical, and its actuator is linked to a series of contacts. If an object gets close to or makes touch with the actuator, this switch will make or break the electrical connection. The limit switch is named after its mode of operation. The limit switch would primarily consist of a spring-loaded push button connected to an electrical circuit. When the object comes into touch with the push button (actuator), the push button is pushed inside, activating the electrical circuit. Following that, the electrical circuit would deliver the signal to regulate the machine element’s motion.

Why is the limit switch important?

Limit switches are a low-cost approach to connecting the physical and electrical worlds. They were invented some decades ago, and their widespread use has greatly reduced their cost to the end user. As a result of their simplicity and low cost, they play a key role in production.

How can we check whether the limit switch is faulty or not?

A basic ohmmeter or Digital Multimeter (DMM) can be used to detect whether or not a limit switch is faulty. Disconnect the system’s limit switch and connect the ohmmeter leads to each terminal. The resistance should be very high if the limit switch is generally open (NO). The resistance should be near to zero if it is typically closed (NC). To measure the resistance, turn the limit switch to the active position. In this case, the opposite should be true. The limit switch is faulty if the transition does not occur.

Advantages and Disadvantages of Limit Switch

Advantages of Limit Switch

  • Limit switches are quite precise.
  • Limit switches consume very little electricity.
  • When compared to sensors, the cost is substantially lower.
  • In open areas, the limit switch can also be employed.

Disadvantages of Limit Switch

  • It is quite likely to fail if it is used for an extended period of time.
  • It is required to make direct touch with the limit switch’s operation.
  • When a device is traveling quickly, it is difficult to notice that thing.

Function of Limit Switch

Limit switches can be found in our household items, including:

  • They are used in microwaves to ensure that the door is properly closed before the operation is permitted.
  • They are used in elevators to alert the system when the cabin reaches the intended floor.
  • Limit switches are used in washing machine lids to allow the wash cycle to begin.