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Limit Switches: How They Work And When To Use Them

limit switch


Limit Switches: How They Work And When To Use Them

Limit switches are a type of sensor that can be used to detect the movement of a part or the presence of an object. They are primarily used in robotics and industrial automation, but they can be used in almost any application where you need a simple switch.

Limits switches operate on the principle that when something is moved beyond a certain point, it will trigger an electrical signal. For example, if you have a robot arm that needs to stop moving whenever it reaches the end of its travel range, you could use a limit switch to detect when this happens. This would help keep your robot from damaging itself or breaking other parts due to over-traveling.

Limit switches come in many different configurations depending on their purpose and application. They can be magnetic or optical sensors, which detect proximity with an electromagnet or light beam respectively. Each type has its own advantages and disadvantages depending on what you want it to do.

Why Use Limit Switches?

One of the most important functions of a limit switch is to prevent damage to the motor, pump, and other equipment. Limit switches are designed to stop the motor from running once it has reached its limits. The purpose of this is to prevent damage to equipment and injury to people. If a machine continues to run after reaching its limits, there is a risk that it will overheat or break down.

Limit switches can also be used for other purposes such as preventing damage from overheating, stopping an engine from running if the oil pressure drops too low, and controlling a machine’s operation based on its position in space (or lack thereof).

When To Use Limit Switches?

Limit switches are most commonly used in industrial settings and to protect equipment against damage from overuse or improper use. They are also used in home appliances like washing machines and dishwashers, which have safety features built into them that rely on limit switches. Some examples of industries where limit switches are common include:

  • Automotive manufacturing
  • Electronics manufacturing
  • Food processing plants (e.g., dairy products)

How Do Limit Switches Work?

Limit switches work by detecting when an object has reached its maximum or minimum position. This can be done by using magnets attached to one end of a bar, which will move freely until they reach the end of their range and then bounce back when they’re released. A microcontroller reads the position of these magnets and turns them on or off accordingly based on where they are positioned within this range.

Types Of Limit Switches

There are two main types of limit switches: optical and mechanical:

  • Optical Limit Switches: These use light beams to detect objects moving past them, often in conjunction with photocells or infrared emitters/detectors. They’re commonly used for detecting objects moving along conveyor belts or falling into containers (e.g., grain silos).
  • Mechanical Limit Switches: A mechanical limit switch is a simple device that uses mechanical contacts to detect the end of travel or the presence of an object. A spring-loaded lever or pin is fitted with a movable contact that makes contact with another stationary contact when the lever reaches its end of travel or when an object comes into contact with it.

Advantage Of Using A Limit Switches

The main advantage of using a limit switch is that it can be used to shut off the machine if something goes wrong. For example, if you are machining something and it breaks, then the limit switch will stop the machine from moving and potentially damaging itself further or hurting someone nearby.

A second advantage is that it can be used to detect when a part has been produced. In this case, there would be no need for a human being to visually inspect every single part. Instead, a sensor could be fitted so that when a certain point was reached by the tool, it would automatically stop the machine and alert an operator that a part had been produced. This could save time and money as well as improve quality assurance procedures in many industries.


Limit switches are not 100% fail-proof. However, they provide a much safer alternative to standard foot pedals, belts, or chains that have been used in the past. Overall, limit switches represent one of the best ways to start with PLCs if you’ve never worked with them before, and once you get the hang of them they can be very simple to use while providing much better safety than other possible solutions.

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