What is Limit switch | Working Principle Of Limit switch | Application of Limit switch


What is Limit switch | Working Principle | Application of Limit switch

Hello friends, today we will talk about what a limit switch is, how a limit switch works, where it is used, and what are its advantages and disadvantages.

What is a Limit switch?

The limit switch is the same type of normal switch that is fitted in our house.

With the help of the limit switch, we can control any device that runs on electricity.

The main function of a limit switch is to observe and control the physical movement of any machine.

For example, suppose a motor is going from left to right and we have to unload something somewhere then we will stop the motor for it. The switch used to stop the motor at such time is known as a limit switch.

Also Read: What is SMPS | Working Principle of SMPS | Advantages Of SMPS | Applications Of SMPS

Where is the Limit switch used?

The limit switch is used extensively in the control system. The limit switch also has a different role in automating our machine. Limit switches are commonly overused in CNC machine robotics and motor control functions.

Apart from this, the limit switch is also used for safety purposes

Parts of the limit switch:

The limit switch consists mainly of 3 parts which are as follows.

#1. Liver/Actuator:
#2. Operating header:
#3. Contact:

#1. Liver/Actuator:

The lever of a limit switch is also called an actuator. This limit is located on the outside of the switch and is attached to the header.

The lever always works up and down. When anything presses the lever of this limit switch, the contact inside the switch operates and the switch starts working.

There are 3 types of limit switch depending on the lever/actuator.

Types Of limit switch

1.Roller Lever
2.Spring Wire

#2. Operating Header:

The lever of the limit switch is mounted on top of this operating header, due to which this operating header operates whenever there is any movement in the lever.

Remember this point:

When there is movement in the lever of the limit switch, it operates the header. In the same way, the NO contact inside the switch also operates when the header operates.

Operating Header

When this switch is turned on or off we get to hear a small sound

With the help of this, while working in the field, we know quickly whether this switch is in working condition or not. If the switch is bad, we will not hear any sound.

#3. Contact:

Limit Switch NO NC Contact

Contacts are made inside the limit switch and with its help, we are able to do the wiring. Control wiring is done inside these contacts.

There are mainly two types of contacts inside the limit switch. One is NO and the other in NC.

Working Principle of Limit switch:

Working Principle of Limit switch

Working of the limit switch- The lever is fitted in the limit switch. And when the device comes in touch with it, this lever rotates. As it rotates, the mini switch inside the limit switch operates.

The mini switch inside the limit switch has an NO and an NC contact.

Difference between NC and NO contacts:

NC contacts- This contact de-energized means connected to each other in the normal state. That is, if you check the NC contact with a multimeter, you will find it in close condition.

NC contacts remain closed in normal condition and open as soon as they are energized.

NO contacts- the same if we talk of NO (Normally open) then these contacts remain open in a de-energized state. That is, if you check the NO contact with a multimeter, you will find these two far apart. NO contacts remain open in normal condition and close as soon as they are energized.

Advantages of installing limit switches:

  • Limit switches are quite accurate
  • Limit switches operate at very low power.
  • The cost is much lower compared to sensors.
  • The limit switch can also be used in open space.

Disadvantages of the limit switch:

  • If it works for a long time, it is very likely to break down.
  • It is necessary to come in direct contact with the working of the limit switch.
  • If a device is moving fast then it becomes difficult to detect that device at that time.

Where is the limit switch used?

  • The presence or absence of any object can be detected.
  • In speed detection.
  • In automation.
  • To know the position or travel limit.


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