Microswitch (Miniature Snap-Action Switch) Explained

Snap-action switches are highly versatile and frequently used in a wide range of applications across various industries, from consumer electronics to mission-critical defense systems. These switches go by many names, including microswitch, micro switch, snap switch, snap action switch, or miniature snap action switch. These switches “snap” from one position to the other the moment the actuator is pressed beyond a set point. 

Today’s article explores the microswitch in depth, including how it works, different types and actuators, and guidance on selecting the right switch for your application.

Snap action switches are compact electromechanical switches with a distinctive snap action design that can quickly open or close a circuit. Like all applications for electronic switches, dependability is critical, and the microswitch is known for being extremely accurate and long-lasting. This type of switch uses a snap-action (i.e., over-center) mechanism, which means the contacts move quickly at a precise point of actuation. This unique design ensures consistent switching, reduces wear, and helps the switch last through countless cycles without fail.

Snap action switches are designed to handle a wide range of electrical loads, from tiny milliamp signals in control circuits to 10–20 amps or more in industrial equipment, underscoring their versatility. As mentioned earlier, this switch may go by many names, but they all refer to the same type of device.

A micro switch provides fast, repeatable, and precise switching using its internal snap-action, over-center mechanism. Applying force to the external actuator (such as a plunger, lever, or roller) causes the internal spring blade to bend and store energy until it reaches a critical point (the “snap”). At this point, the moving contact rapidly flips between terminals, where the shared common (COM) terminal connects either to the normally open (NO) or normally closed (NC) terminal (depending on the switch state). The amount of force necessary to reach this point is the Operating Force (OF), and this phase of the actuator movement is the Pre-travel (PT).

The switch can be pressed slightly farther without damage after actuation, which is referred to as the Over-travel (OT). When released, the mechanism relaxes, snaps back, and returns the moving contact to its original position. The force at which this reset occurs is the Release Force (RF), and the small distance between the actuation point and release point is known as Differential Travel (DT).

Microswitches can handle a wide range of electrical loads, from low-level signal currents in electronic circuits to higher current applications in industrial equipment. In many applications, especially in harsh or safety-critical environments, toggle switch guards may be added to protect the actuator from accidental engagement or physical damage.

There are three main aspects of actuators, including the form factor (size), actuator style, and contact configuration. Additional characteristics that can affect installation, durability, and application are the termination and mounting options, sealing, and environmental ratings.

The actuator size determines a microswitch’s physical footprint and current capacity within the application. There are three size classes of snap switches: subminiature, miniature, and standard.

• Subminiature: This microswitch snap action is very compact, typically <10–15 mm per side, making it ideal for tight spaces in electronics and portable devices. Subminiatures are usually rated for low currents: <0.5 A, 30 V DC.
• Miniature: These mini switches are slightly larger in size (approx. 15–20 mm per side), which balances durability and size. The miniature snap action switch is typically rated 1–5 A at 125–250 V AC/DC, making them suitable for control panels. 
• Standard: These full-size snap action switches are approximately 20–30 mm per side. Rated for higher currents (up to 15 A) and voltages, these snap switches are ideal for industrial equipment and heavy-duty circuits.

Microswitches offer various actuator styles to accommodate differences in travel distance, precision, and mounting space.

• Plunger: Offers a straight design with precise actuation. The plunger works well in applications with limited space that require perpendicular engagement.
• Hinge Lever: This actuator pivots around a fixed point, which offers some mechanical advantage. The hinge lever works well for side actuation and slightly longer travel.
• Simulated Roller: This actuator style mimics a roller lever and reduces friction for smoother engagement. The simulated roller is a variant of the hinge/lever actuator and features a small, non-rotating, rounded tip. It’s suitable for side-actuated microswitches in compact mechanisms or applications where space restraints can’t accommodate a full roller lever.
• Roller Lever: The roller lever features a pivoting arm with a small rotating roller at the end. This design reduces actuation force and wear, making it ideal for moving cams or sliding components where the actuator may be engaged from the side.
• Leaf Lever: Offers a thin, flexible actuator arm that bends to engage the microswitch’s internal snap-action. This design makes it ideal for mounting in constrained spaces.

There are a variety of contact configurations available to suit different electrical needs. 
The most common type is the SPDT (Single-Pole Double-Throw), which, depending on the actuator's position, features a shared COM terminal that connects to either the NO or NC terminal. Other, more straightforward configurations include SPST-NO and SPST-NC, which function as simple ON or OFF switches.

The material used for a microswitch’s contacts plays a key role in its performance. Silver contacts are durable and handle higher current loads effectively, while gold contacts are ideal for sensitive, low-current signal applications. Also, factors such as contact bounce and inrush currents should be taken into account, as they can influence the reliability and lifespan of the switch.

The termination connects the snap switch to circuits, and common types include: 

• Solder Lugs: permanent, secure connections using standard soldering techniques
• Faston Terminals: no soldering required for quick assembly and easy replacement 
• PCB Pins: directly integrates the switch onto a printed circuit board
• Screw terminals: offer more flexible wiring for industrial applications

The microswitch’s mounting style can impact alignment, stability, and actuator engagement. The two main types are PCB or panel mount. The PCB-mounted switches save space by sitting directly on the board, while the Panel-mounted switches attach to enclosures or machinery using screws or brackets for easier access. There are some microswitches with integrated mounting holes, clips, or brackets that can accommodate both mounting styles.

Sealed versions of microswitches are needed for applications exposed to dust, water, or washdown environments, and they are rated IP40–IP67 depending on dust and moisture protection. 

Selecting the optimal microssitch for an application involves several considerations, such as the purpose, electrical rating, mechanical characteristics, environmental durability, and compliance requirements. Following is an outline of items to consider during selection:

Step 1: The Purpose
Determine what the switch is meant to do, i.e.,  what device or system it's meant for. Also, consider contact bounce for sensitive applications.

Step 2: Electrical Rating
The switch’s voltage and current ratings should match the load. Also consider AC vs. DC circuits and check resistive vs. inductive loads.

Step 3: Contact Type and Material
Silver contacts can handle higher currents and general use, whereas gold is better for low-level signals and corrosive environments. Also, consider if you need SPDT, SPST, or DPDT.

Step 4: Actuation Type: 
Determine which type of switch is needed based on your application’s mechanical setup, e.g., plunger, lever, roller, etc.

Step 5: Environmental Conditions
This includes the switch's temperature range, humidity, dust, or chemical exposure, and the 
IP rating or sealing requirements for harsh environments.

Step 6: Mechanical Durability
Check the number of actuations the switch can withstand over time, as well as its resistance to vibration, shock, and wear.

Step 7: Review Size and Mounting Options
To fit the available space, select a mounting style that accommodates the micro switch's fit and integration.

Step 8: Compliance & Safety Standards
Common safety compliance markings include: UL, cUL, EN/IEC 60947-5-1, and RoHS/REACH indicate material and environmental compliance. 

Step 9: Test and Validate 
To ensure performance and reliability, test the switch under real-world conditions.

Peerless Electronics is an authorized dealer for today’s leading switch manufacturers, ensuring quality and reliability. We carry a wide selection of reliable switching solutions, including microswitches, and offer over 50 value-added services with every purchase. At Peerless, we make it easier to get exactly what you need, faster and smarter. 

What are microswitches used for?

Mini switches are used in numerous applications across industries to enable ON/OFF switching with precise actuation, as well as provide interlocks and detect positions.

What’s the difference between a microswitch and a limit switch?

Microswitches are small, snap-action switches, while limit switches are larger devices often containing a microswitch inside.

How many cycles do microswitches typically last?

The electrical life depends on the snap switch's size, load types, operating environment, and quality. For example, subminiature microswitches can average 1–3 million mechanical cycles, while miniature or standard microswitches can average 5–10 million mechanical cycles.

Gold vs. silver contacts—what’s best for low-level signals?

Gold contacts are best for low-level signals.

How do I test a microswitch with a multimeter?

Begin by setting the meter to continuity or resistance mode, then connect the probes to COM and either NO or NC. Activate the switch to obtain the reading, which should change state (from open to closed or vice versa) at the snap point.

Can I cross-reference one microswitch series to another brand?

Yes, you will need to match electrical ratings, actuator style, form factor, mounting, and termination options when switching brands.