Limit Switch Explained | Working Principles

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In this video, we’re going to introduce you to a device called a Limit Switch.

There’s probably not a day that goes by where you don’t use or encounter a limit switch at home, or at your workplace.

There are 4 general types of limit switches: whisker, roller, lever, and plunger.
Depending on the application, a limit switch may be a combination of 2 of the general types such as roller-lever.

A limit switch is an electromechanical device operated by a physical force applied to it by an object.

The limit switch is used to detect the presence or absence of an object.
These switches originally used to define the limit of travel of an object, and as a result, they were named Limit Switch.

When you open the fridge door, a light comes on inside. A limit switch is used to detect if the fridge door is open or closed.

On many overhead garage doors, there is a limit switch that stops the movement of the door when it reaches its fully opened position.

A limit switch is an electromechanical device consisting of an actuator mechanically linked to an electrical switch.
When an object contacts the actuator, the switch will operate causing an electrical connection to make or break.

Limit switches are available in several switch configurations: Normally Open, Normally Closed, or one of each.

Depending on the origin of the electrical schematic, you may see limit switches drawn in different ways.
The International Electrotechnical Commission (or IEC) and the National Electrical Manufacturers Association (or NEMA) have slightly different symbols.

Let’s have a look inside a microswitch that is a type of limit switch.

A microswitch has 2 limit switches operating together and sharing a common terminal. One limit switch is normally open and the other is normally closed.

To be technically correct, the switch configuration is Single Pole Double Throw, or commonly referred to as SPDT.
The dashed line indicates that both switches are mechanically connected and will operate at the same time.

Alright, let’s connect the microswitch to a lamp circuit. In the inactive state, the Red lamp is on as the device is not being operated by an object pushing on the trigger.
When the Trigger is pushed the device will activate, and the Green lamp will come on.

Now that you’ve seen the limit switch in action you are probably thinking about some of the applications where you have seen them in action.

For example, you might see a limit switch operated by a container on an assembly line, or operated by a rotating machine part or by any number of other moving mechanical objects.

A limit switch could be used to count passing objects, or determining the position of a hydraulic cylinder.

Limit switches are slowly starting to disappear from many industrial applications. They are being replaced by proximity sensors.
Unlike a limit switch, a proximity sensor has no mechanical moving parts.
A proximity sensor performs the switching action with electronic switches.

Limit switches will not completely disappear any time soon as they outshine their proximity switch counterpart in their ruggedness and reliable operation in difficult environments.
Generally speaking, limit switches are capable of handling much higher current values than proximity sensors.

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[_desertwalker_]

Using the light globes to demonstrate how they worked brought it home for me. Many thanks.

[jedijedi]

Your videos are extremely helpful and very well explained. Thank you for your efforts in teaching us automation concepts. Good luck and cheers!

[yongkim]

I'm working in control valve company. very helpful clips.many thanks🙏

[roseelectronics]

The best technical video channel. Truly

[nabillaazzahra]

Wow the video is very useful, thank you, I'm a student from Indonesia🇮🇩

[loco]

Excellent. Thanks.

Maybe machine safety would be a good next topic to discuss. I.e saftey limit switches, door locks, interlocks, push buttons, light curtains, saftey monitoring relays, saftey contactors etc. Thanks

[samsarajunvianto]

thank you for the content, it is very useful for me, an electrical student, greetings from Indonesia 🙏

[kor_js_kim]

For your better understanding, the limit switch is devided in two parts mechanical and electrical parts. in the application, if you want to proper goods, please remember the mechanical parts related "how the mechanism works", and electrical parts deal with "system capacity" such as current and voltage rate. Espatially in the motor involved one, you can calculate inducted current level with the power facter. lats of cases has burning issue of contacts for too high electric level. thank you for the great information and good luck for everyone who wants to know limit switches! :)

[TraficoAereo-ct]

thank you, you save my life, with your information thanks! :D

[arieskurniawan]

thanks for the content, I'm a student from Indonesia.

[galang]

Thanks for information about limit switch, because i will learn it at my Vocational High School.🇮🇩🇮🇩🇮🇩

[atirjan]

Great information about limit switch ❤❤

[mfarhan]

this video contains a lot of knowledge, very good very good

[fadlifatih]

Nice video information, very well on explained and this is so helpful for me! Thankyou.

[-muhammadawaluddin]

Thanks for the information, this video is great.

[anikettripathi]

Great. Giving true information gives happiness. Best wishes.

[BillupsIniestaC]

Awesome presentation. Total noob here learned what a limit switch is and does in like 3 minutes.

[dilawarejaz]

Very well elaborated۔ Really informative for beginners

[putrasyabh]

That's good, thank you for information and all everything for students in indonesia keep goin mr abi 🙏🙏👌

[Wirenutz]

Going to start a limit switch conservancy group 😋