What is a Micro Switch : Working & Its Applications

Micro-switches have become essential parts of the sensing & control community of different fields like industrial, agriculture, construction, transportation, and commercial. So there are trillions of micro switches used in industrial equipment, construction or agriculture machinery, & control systems around the world. These switches are simple and small devices including two contacts like NO and NC which are connected with a snap-action switching mechanism. These switches are capable of performing safely, reliably, and accurately in several harsh environments. So this article discusses an overview of micro switch – types with applications.


What is a Micro Switch?

Micro switch definition is: It is  a small and very sensitive switch that activates by using minimum physical force is known as a micro switch or miniature snap action switch. This is one kind of momentary contact switch which is widely used as a sensor in industrial, medical instruments & automotive.

Micro Switch
Micro Switch

The switches are frequently used in switch panels & home appliances with small buttons. These switches are normally economical & they can work for a long time. These switches can be used as safety devices because they are sensitive and reliable. The micro switch symbol is shown below.

Micro Switch Symbol
Micro Switch Symbol

The micro switch includes three pins common (C), normally closed (NC), and normally opened (NO). Here, the common pin is an input pin, the NC pin is output1 and the NO pin is output2.

Micro Switch Construction

The construction of a micro switch can be done by using different components like plunger or actuator, cover, moving piece, support, NC terminal, NO terminal, contact, and, moving arm.

Micro Switch Construction
                Micro Switch Construction

Plunger

The plunger is also known as an actuator which is one type of mechanical component, used to control a circuit manually by turning ON & OFF.

Cover

The cover of the switch protects from external forces.

Moving Piece

The moving piece used to apply the operating power to the contacts is known as the actuator.

Support

This is used to give support to the micro switch.

NO Terminal

NO terminal is also known as a normally open terminal. Here, NO terminal specifies the contact of the switch will be open by default. So, if you connect it within a circuit, there is no flow of current within the circuit.

NC Terminal

NC terminal is also known as a normally close terminal. It is the opposite function of the NO terminal. The contacts of the switch will be in closed condition. So it allows the flow of current throughout the circuit.

Contact

The contact in a switch is an electrically conductive material piece, normally metal. The main function of this part is to make or break electrical continuity.

Moving Arm

The moving arm is a lever in a switch, used to activate & operate the micro switch.

Working Principle

The working principle of a micro switch is, that once this switch touches an object, then contacts will change their position. So this switch working principle mainly includes the following.

When you press the lever of the switch, then the circuit’s normally closed pin will be opened, and the normally opened pi will be closed. Similarly, when you open the lever of the switch then the circuit’s normally close or NC pin will carry current whereas normally open or NO circuit can insulate electrically.

In addition, the fundamental feature of the micro-switch is the tipping-point mechanism. So this feature will help to generate particular trips and reset points wherever contacts will change the condition.

Features of Micro Switches

The features of micro switches include the following.

  • It is a snap-action precision changeover switch including a tiny contact gap.
  • This switch is well suited for logic-level & power-duty loads.
  • Includes switch options like SPDT, SPNO, or SPNC.
  • Power duty switching through silver alloy contacts.
  • Different electrical terminations.
  • Silver alloy or gold-plated contacts for logic-level control.

Micro Switch Circuit

The circuit diagram of the micro switch includes the following, The following circuit can be built with a micro switch to control two leds with a battery. Generally, the micro switch includes three terminals like C, NO, and NC. The connection of this circuit can be done like the circuit shown below.

Micro Switch Circuit Diagram
Micro Switch Circuit Diagram

Once the lever is pressed, the common terminal and NC terminal of the switch are connected. So there is no connection to NO terminal of the switch. As a result, the Green color will turn ON

Similarly, once the lever is opened, the common terminal and NC terminal of the switch are connected. So there is no connection to the NC terminal of the switch. As a result, the Blue color LED will turn ON. Based on the application, we can use this switch in NO or NC mode.

Micro Switch Vs Limit Switch

The difference between micro switch and limit switch includes the following.

Micro Switch Limit Switch
This is a small and very sensitive switch. This is an electromechanical device.
This switch is also known as a miniature snap-action switch. This switch is also known as the end switch or position switch.
The function of a micro switch is to switch an electrical circuit ON/OFF or to close a circuit automatically because of a mechanical load. The function of the limit switch is to sense the object’s presence or absence.
A micro switch includes two limit switches like NO and NC which operate together & sharing a common terminal. A limit switch can be operated through the presence of an object or motion of a machine part.
The types of micro switches are; pin plunger, spring pin, spring short, panel mount, leaf spring, leaf lever, roller leaf spring, etc. The types of limit switches are whisker, roller, lever limit, and plunger.
It has less contact gap. It has a high contact gap as compared to micro switch.

Micro Switch Types

There are different types of micro switches available in the market like pin plunger, spring pin plunger, spring short plunger, panel mount pin plunger, panel mount roller pin plunger, leaf spring, roller leaf spring, leaf lever, simulated roller leaf lever, hinge lever, simulated roller lever, hinge roller lever, reverse operation hinge lever, reverse operation hinge roller lever, rotating operation and flexible rod. Some of them are discussed below.

Hinge Roller Lever

A hinge roller lever switch normally includes a roller that connects to its hinged lever. So this switch is applicable for high-speed camera operation.

Hinge Roller Lever
Hinge Roller Lever

Rotating Operation

These types of switches are common with low-torque actuators. So, this kind of switch is applicable for recognizing light objects such as paper currency.

Rotating Operation
Rotating Operation

Pin Plunger

The pin plunger micro switch is perfect for direct, short strokes. Thus, it can be used to detect high-precision positions directly In addition, this kind of switch requires a consistent stopper because its overtravel has the shortest actuator.

Pin Plunger Micro Switch
Pin Plunger Micro Switch

Leaf Spring

The leaf spring micro switch includes a more significant stroke due to the powerful leaf spring. So, you can use it for low-speed cams or cylinder drives. In addition, it is very important to maintain the overtravel switch in a specification of application for two important reasons to avoid damage & second one is due to the leaf spring having a permanent bearing point.

Leaf Spring Micro Switch
Leaf Spring Micro Switch

Spring Pin Plunger

As compared to a pin plunger, a spring pin plunger has a longer overtravel. But you can also utilize this switch for similar applications. When using this switch, make sure the load is on the center of the plunger and this is due to the plunger’s diameter being somewhat larger.

Spring Pin Plunger
Spring Pin Plunger

Panel Mount Plunger

As compared to other types of switches, this microswitch has the biggest overtravel. This switch can be mounted to a panel through a nut and hexagonal locknut. After that, you can control this switch manually or mechanically. In addition, this switch can be used with a low-speed cam.

Panel Mount Plunger
Panel Mount Plunger

Maintenance of Micro Switches

The maintenance of micro switches can be done like the following.

  • These switches must be maintained very clean, especially since the actuator region is mainly sensitive.
  • It is not suggested to utilize chemical cleaning liquids like aqueous solution on the microswitch..
  • These switches should not use in an environment that has explosive or combustible gases.
  • The touch parts of the microswitch need to check frequently to observe if the touch of the switch is okay or not, whether the limit distance is within the range & the strength & touch speed are normal.
  • Need to check the periodic detection of voltage and current of the circuit otherwise, the current & voltage will have a huge impact on the switch so it will get damaged. So the voltage stability is very significant.
  • In automation equipment, we need to check this switch regularly for 2 to 3 months to observe if there is any damage to the external power to avoid other consequences.

Micro Switch Advantages and Disadvantages

The advantages of the micro switch include the following.

  • Accurate performance.
  • Arcing damage can be reduced by arcing fast switching speeds.
  • Reliable switching.
  • Inexpensive.
  • Less maintenance and long life.
  • These switches are versatile.
  • Resistant to water & dust.
  • Durability.

The disadvantages of micro switches include the following.

Most of these switches face some issues like low-quality parts or components. The faults that can affect a micro switch are components getting burnt, depreciation, stops working suddenly.

Applications

The applications of the micro switch include the following.

  • Micro switches are applicable in industrial areas.
  • These switches are used to create time mechanisms once they are used with the combination of a variety of devices.
  • These are used in our daily life like home appliances, cars, industrial equipment, etc.
  • These are used as control switches, limit switches, etc.
  • These switches help in detecting paper jams in printers.
  • These switches are used within control circuits of different appliances like small-size motors, lamps, solenoids, etc.
  • These are used as a jam detector in vending machines & also to detect coins once entered into the machine.
  • These are mainly used to detect the open-close position of the valve.
  • These switches are used as security apparatus in lifts and door interlocks in microwaves

Thus, this is all about an overview of a micro switch – working with applications. The features of this switch include compact size, boosted service life, less sensitivity to vibrations & high accelerations, increased electrical properties, etc. There are different types of microswitches but their selection mainly depends on the requirement. But it is significant to connect these switches properly in your application to get the best results. Here is a question for you, what is the roller leaf spring switch?

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