A limit switch is a mechanically made device that has an actuator, which senses the pressure of any moving object that moves towards it. In electrical engineering, its operation occurs when there’s a movement of a machine or existence of an object.
When actuated, these switches can be used to energize or de-energize an application. In an electrical connection, they make or break it when there’s an object in contact with the actuator. You can find them in residential and industrial markets.
Limit Switches act as some sensors that detect existence and absence. Precisely, mechanical limit switches are mechanically activated. This automatic activation means they have some knob, lever or plunger that’s physically activated when connected with another object.
When the object comes into contact with the actuator switch, it eventually moves the actuator to the ‘’limit’’ when there’s a state of change within the connections. There are other variables of existing switches such as light sensors, electric switches, and others.
How does a Limit Switch Work?
Its working principle acts like this. A Single Pole Double Throw (SPDT) switch which only generates a single input that can connect and switch between both outputs. It means there’s one and two input terminals.
The Normally Open contact, NO, is always open when the plunger is free. The Normally Closed contact, NC, is closed when the plunger is free and COM is common.
A plunger is a mechanism or part of a device that plunges or thrusts movements.
NO will generally be open to COM. On the other hand, NC opens to COM.
There’s a connection between C and NC and NO disconnected when there’s no pressing in the plunger.
There’s a connection between C and NO and a when the plunger is pressed there’s a disconnection.
Uses of Limit Switch
A limit switch is merely a switch mounted on specific locations to be actuated by an object instead of a human being. Some of the primary functions of a limit switch are:
2-Detecting a travel limit and positioning.
3- Speed Detection
4- Detecting presence or absence
5- Within the residential homes, limit switches are in the most common appliances such as the refrigerator. When the electromechanical device turns the light on inside the fridge is opened. In this situation, when the limit switch is depressed, the light will turn off.
6- In the industries, limit switches are used in the assembly and actuated by the movement of a machine part or the presence of an object. The limit switch activator is installed with different options such as plunger type, roller and more.
7- Additionally, they are used in safety equipment such as solenoid locking and key operated interlocks.
Types of Limit Switches
The performance of a limit switch will depend on some factors. They include a mounting method, size, force capacity of the switch and the stroke rate used during the operation. It’s essential for the limit switch rating to match its intended use. The major types of limit switches used in the industries are:
1- Snap Switches
Used in an application that requires basic contact parameters. It does or doesn’t need an operator.
2- Miniature Enclosed Reed
This limit switch is formed from die-cast Zinc; it’s also known as Type XA. It’s suited for applications that require elevated environmental stresses.
3- Heavy Duty Precision Oil-Tight
Also called the type C limit switch, it’s very reliable due to its long mechanical and electrical lifespan.
4- Heavy Duty Oil Tight and Foundry
The heavy duty oil tight and foundry is majorly used in factories and mills.
5- Gravity Return
Generally used in the production line and conveyor operations involving small light components. There are different varieties such as the lever type, roller-type, and roller type.