Principles, Applications, and Selection Guide

1. What is a microswitch?

A microswitch, also known as a sensitive switch, is an electromechanical switch that triggers circuit closure or opening through a small displacement. Its core features are:

Short travel: Typically requires only 0.1 to 0.7 mm of physical displacement to activate;

Snap-action mechanism: Internal spring structure enables “instantaneous switching,” reducing arc loss;

High precision: Repeatability error can be controlled within ±0.02 mm.

Technical tags: Snap-action contacts | Instantaneous switching | Long electrical lifespan

2. Core Structure Analysis

The precision of microswitches stems from their three-layer structural design:

1. Actuator

Lever-type/roller-type/button-type, etc., transmit external force to the internal mechanism;

Example: Elevator buttons use a long lever arm structure to achieve light-touch triggering.

2. Snap-Action Spring System

Utilizes spring energy storage to achieve instantaneous contact switching (action time ≤ 10 ms);

Avoiding arc erosion caused by slow contact between contacts.

3. Sealed Contact Chamber

Silver alloy contacts (AgCdO/AgNi) are enclosed in an inert gas or vacuum chamber;

Protection rating up to IP67, resistant to dust, oil contamination, and chemical corrosion.

III. In-Depth Application Scenarios

1. Safety Protection Field

Machine tool safety door lock: power supply is cut off when the door moves 0.5mm (complies with ISO 13850 standard);

Elevator level detection: Reed microswitch accuracy of ±0.3mm ensures safe stopping.

2. Smart Home Control

Washing machine door cover detection: IP67 sealed switch prevents moisture and foam penetration;

Air fryer temperature safety: Dual metal strip + microswitch dual overheat protection.

3. Automotive Electronic Systems

Brake Pedal Position Sensor: 2 million cycles lifespan ensures zero signal errors;

New Energy Vehicle Charging Gun Locking: High-voltage interlock (HVIL) critical component.

IV. Selection Pitfall Avoidance Guide

Avoid Common Design Mistakes:

1. Travel Matching Error

Error Case: Mechanical arm limit switch without overtravel allowance → mechanism jammed, causing switch failure;

Solution: Select a model with ≥20% travel allowance (e.g., if 1mm travel is required, choose a 1.2mm model).

2. Insufficient load capacity

Misconception: Using a signal-grade switch (0.1A) to control an electromagnetic valve (1.2A) → contact welding;

Golden rule: Actual current ≥ 30% of the switch's rated current (e.g., if the load is 1A, select a model with ≥3A).

3. Lack of environmental adaptability

Food machinery selection: Must have a stainless steel housing + food-grade lubricant (NSF H1 certified);

Chemical industry applications: Fill the sealed chamber with nitrogen to prevent hydrogen sulfide corrosion of the contacts.

5. Cutting-edge technology trends

1. Contactless Upgrade

Hall effect microswitch: magnetically triggered, completely eliminating mechanical wear (lifespan > 100 million cycles);

2. Intelligent Integration

Switch with IO-Link interface: real-time feedback on contact wear status, predicting replacement cycles;

3. Miniaturization Breakthrough

SMT-mountable microswitches: dimensions as small as 6×3×2.5mm (e.g., Panasonic ADBS series), suitable for TWS earbud housing detection.

Though small, microswitches serve as the “last line of defense” for system safety. Precise selection not only ensures functional implementation but also upholds safety responsibility.