A Guide to Micro Switches

Reviewed by Stephen Bettles (Technical Support Engineer, January 2025)

Micro switches offer reliable and precise switching capabilities, making them a popular choice in various industries. They are known for their durability, long lifespan, and ability to operate under harsh conditions. With their compact size and versatile functionality, micro switches play a crucial role in the operation of many electronic devices and systems. They are used in everything from refrigerators and air conditioning units to lift buttons and door locks. These versatile switches are also used in robotics to control motion.

Our in-depth guide will equip you with knowledge about micro switches, how they work, micro switch types, testing procedures, wiring methods, and some of the typical applications of micro switches.

Micro switches are compact electrical switches prevalent in various industries and applications. The term 'micro' denotes the component's small size and sensitivity, ideal for restricted spaces. Micro switches are designed to operate over a long period of time (for tens of millions of cycles in some heavy-duty cases). They are quick to operate and very reliable. Micro switches typically make a distinctive ‘click’ when pressed, providing feedback to the device user, and can be triggered with minimal physical force.

Micro switches are electromechanical devices. The simplest type of micro switch toggles between the 'on' and ‘off’ positions by moving a spring-loaded lever. When force is applied, the lever moves from the centre of the switch to either the on or off position.

Micro switches are typically utilised to detect the presence or absence of an object, to control machinery, or to provide safety interlocks. The first micro switches were developed in the US in the 1930s and have since seen significant advancements in design, materials, and functionality. Today, micro switches are found in a multitude of applications that demand a dependable and precise switching mechanism. They are used in appliances, automotive equipment, the aerospace industry, industrial machinery, and a host of other electronic devices.

Micro switches have revolutionised engineers' and designers' capacity to integrate reliable switching functionality into a wide array of products. These switches play a critical role in proper operation and user safety.

Understanding how micro switches work can help you make informed decisions when selecting and implementing them in your projects.

At their core, micro switches usually feature an actuator, a set of electrical contacts, and a spring-loaded lever. When the small lever or button mechanism is pressed or comes into contact with force, it moves a spring-loaded contact inside the switch. This causes the electrical contacts to make or break the electricity flow, opening or closing the circuit.

This simple yet effective mechanism allows micro switches to detect and respond to changes in physical conditions. It's also reliable, ensures switch stability, and can be repeatedly actuated without performance loss.

Inside the switch housing, there are typically three terminals: normally closed (NC), normally open (NO), and common (C). In the normal condition when the switch is in its resting state, the actuator is not pressed and the common terminal is connected to the normally closed terminal. However, when the actuator is pressed, the common pin disconnects from the NC terminal and connects to the NO pin. This change in circuit connectivity enables the switch to perform its intended function.

The precise and consistent switching action makes micro switches ideal for applications requiring accurate control.

There are different micro switch types on the market. Understanding the different types of micro switches can help you select the right one for your specific requirements.

They include:

• Basic micro switches: These are the most common type of micro switch, typically used in applications requiring a simple on/off function. They are compact, durable, and long-lasting
• Subminiature micro switches: These switches are smaller than basic micro switches, often used in applications where space is limited
• Sealed micro switches: These switches are sealed hermetically to ensure resistance to dust, water, and other environmental factors. They are commonly used in demanding conditions such as corrosive atmospheres or harsh industrial environments
• High-temperature micro switches: These switches are designed to withstand high temperatures, often used in applications exceeding the capabilities of basic micro switches
• Pin plunger, spring short plunger, and spring pin plunger types: These are activated by a straight push motion, ideal for precision applications such as measuring air or gas flow
• Leaf levers and roller leaf springs: Roller micro switches use a roller attached to a lever for smooth actuation. These are typically used in machinery and conveyor applications

Each type of micro switch has unique features and benefits. Consider factors such as application requirements, environmental conditions, and desired lifespan when choosing the right micro switch for your project.

When selecting micro switches for your specific needs, it's essential to consider factors such as operating force, electrical ratings, and environmental conditions. By understanding how micro switches work and their circuit details, you can make informed decisions to ensure optimal performance.

When evaluating micro switches, there are several key characteristics to consider:

• Whether the circuit is AC or DC and the level of voltage and current. An overloaded micro switch may fail. Since reduced energy consumption is desirable in electronics design, it may be necessary to specify a micro switch that works at low current levels
• The micro switch's longevity. Some micro switches are designed to last for many cycles before they fail. Durability can be achieved by using certain materials in the micro switch design, such as fibreglass, rubber, nitrile, steel, or zinc
• Micro switch dimensions. Micro switches are available in various shapes and sizes, including miniature and sub-miniature designs. Size impacts how much current the micro switch can handle, with larger current applications needing a bigger micro switch
• The operating environment. Technicians working with micro switches also need to specify a switch with the environment in which it works in mind. For example, if the operating environment is humid, corrosive, or involves water exposure, specific designs are available
• Actuator type: Different actuator types are available, including lever, roller, spring, button, and plunger. The actuator type determines how the switch is activated and impacts its suitability for specific applications
• Contact configuration: Micro switches can have different contact configurations, such as normally open (NO) or normally closed (NC). This determines the state of the switch when it is at rest and affects how it responds to external stimuli
• Terminal type: Micro switches can have different terminal types, such as lugs, screws, solder terminals, quick-connect terminals, or PCB mounts. The terminal type affects how the switch is connected to the circuit and impacts ease of installation
• Ingress Protection (IP) rating: This rating indicates the level of protection the micro switch offers against intrusion by solid objects and liquids. Ratings are applied to a wide range of subjects, including dust, chemicals, and water. IP ratings are particularly important in applications where the switch may be exposed to harsh environments

You may be wondering how to test a micro switch. Safety is the number one priority. Before you test, ensure you are wearing the correct PPE such as eyewear and gloves, have insulated tools to hand, and have turned the power off. Use a voltage tester to confirm there is no voltage: Don’t presume the circuit is dead until you have verified it with a voltage tester.

One of the best ways of testing a newly wired switch is using a multimeter in continuity test mode. Before you test the micro switch, you can check that this mode is working by touching the multimeter probes, which should produce a beep. This indicates a complete circuit.

The next step is to disconnect the switch to isolate it, to ensure your test is accurate. Finally, connect the multimeter probes to the appropriate terminals (normally the common and NO). If the switch is on and functioning correctly, the multimeter should emit a beep when the actuator is pressed.  

If the switch isn’t working, the micro switch position or micro switch wiring may need to be changed. Don’t forget that your micro switch wiring diagram should feature the correct micro switch symbol.

Various types of micro switches and detector switches are used in a wide range of applications across different industries:

• Building and automation: Micro switches are essential in building automation systems, used in door and window sensors, lift controls, and HVAC systems
• Security: Micro switches are used in alarm systems, motion detectors, and emergency stop buttons. Their reliable performance and precise actuation make them ideal for these critical applications
• Industry: Micro switches find extensive use in industrial equipment, machinery, and robotics. They are commonly employed in limit switches, which control the movement and positioning of various components
• Safety: Control panels and safety interlocks also use micro switches. Their compact size, durability, and ability to withstand harsh environments makes them ideally suited to industrial applications where safety is paramount
• Automotive: Micro switches are used in car door handles, seat belts, door locking systems, and brake pedals for proper functioning and safety

Micro switches can also be designed for high sensitivity. Models of this type can be applied to highly precise equipment, such as equipment that measures air or gas flow within a system. Additionally, they can be used as part of a system to detect temperature and pressure.

Micro switches offer several advantages. Their small size allows for flexible and compact designs for various devices and equipment. They are also known for their long lifespan and high durability, making them suitable for demanding environments. Micro switches have excellent electrical conductivity, ensuring reliable performance even in low-voltage applications. Furthermore, their snap-action mechanism provides quick and accurate switching, resulting in precise control and feedback.

Need switches? We stock an extensive range of push button switches and components.

At RS, we offer a wide range of micro switches that cater to different requirements and specifications. With a wide selection of brands and models, you can find the perfect micro switch for your specific application needs.

Our selection includes different sizes, configurations, and actuator types to suit various applications. Whether you need a micro switch for industrial machinery, appliances, or automotive systems, we have the right solution for you.

Browse our range of micro switches today to find the right switch for your needs.