What is a Limit Switch and How does it Work?

Limit Switch is a type of sensor that identifies presence and absence. The limit switch can be mounted into remote locations so that it is moved by an object aside from using a human operator.

How does a Limit Switch Work?

1- Limit switches have many functions, including the following: 
2- Detecting the presence or absence
3- Identifies the range of movement and counting
4- Detecting the positioning & travel limit
5- Breaking a live circuit in case of the apparent unsafe condition
6- Detecting the speed



Different Uses of limit switch

The use of limit switch can either activate (turn on) or deactivate (turn off) an electrical circuit. Most limit switches are used in industrial companies and household appliances.

1- Use of limit switch in Industrial companies 

In industrial companies, limit switches to shut off when an action exceeds its travel or position. An example would be when a robot malfunction occurred- the limit switch will shut down the power to the movement control.

2- Use of limit switch in the home. 

You can see a limit switch at work when you open and closes a refrigerator.  The limit switch limits the light by turning it off when you close the refrigerator, then the light operates on when you open the refrigerator. This is also the same when it comes to washing machines. When you open the top lid, the agitator stops its motion. The limit switch that sets just under the top frame cover, removes the control voltage from the circuit and stops the operation during the mid cycle. This type of use for a limit switch is also known as a safety limit.


Different types of Limit Switch

The common limit switch types are the following:

1- Heavy-Duty Precision Oil Tight (Type C limit switch)

This type of limit switch is commonly used due to its long mechanical and electrical life span. It is easily installed and has a straightforward wiring arrangement, which makes this type recommended to be used in an industrial setting.

2- Heavy-Duty Oil-Tight and Foundry (Type T) 

This type is more upgraded than the type C limit switch.  It can withstand high trip and reset forces, and at the same time can handle operating sequences which Type C can’t handle. This limit switch type is also commonly used in foundries and mills.

3- Snap Switches

Snap switches are used to trigger as soon as the mechanism attached to the switch has moved a predetermined distance, regardless of the speed at which the moving part travels. It is commonly used in applications that require only basic contact parameters, which can work with or without an operator. Snap switches are best used in machines that have short movements or a slow rate of operation.

4- Gravity Return 

Like what the name implies, this type mostly relies on gravity to reset its contact switches by exerting a force on a lever arm and usually works with a low level of torque. There are different types of gravity return switches, which includes spring return, roller-type, lever type, top push, and maintained contact designs. Gravity Return is usually used in production line and operations with small components.

5- Miniature Enclosed Reed

Last but not the least, this type of limit switch is smaller and less expensive compared to the mentioned types above. Miniature enclosed reed contains a contact array featuring a hermetically sealed reed, which makes this type suited for applications that require a high level of contact reliability.


Pros and Cons of Limit Switches

Limit switches are a practical solution for sensing in most scenarios, however, there are some disadvantages when using limit type switches. Here are the Pros and Cons of using limit switches:

Pros: 

  • Can switch currents up to 10A
  • Has an economic sensing solution 
  • Very precise and accurate 
  • Can be used in almost any type of environment 
  •  It only consumes a little amount of electrical energy

Cons: 


  • The mechanical component can easily wear out 
  • You must make a physical contact with an object to activate it 
  • Restricted only to equipment that is operating at relatively low speeds.

Depending on what machine and environment setting you will be using, proper usage of limit switches can definitely help a lot in your home or in an industrial setting.

Location: India

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