SPST vs. SPDT vs. DPST vs. DPDT Micro Switch: Comparison Guide & How to Choose the Right One

Micro switches are critical components used in automotive electronics, smart appliances, industrial automation, and IoT devices. But when it comes to selecting the perfect configuration, one question always arises: SPST vs. SPDT vs. DPST vs. DPDT micro switch — which one is right for your application?

In this guide, we break down each type with clear diagrams, side-by-side comparisons, wiring tips, industry applications, and a step-by-step selection checklist.

What Is a Micro Switch?

A micro switch (also called a snap-action switch) is a precision electromechanical device that opens or closes an electrical circuit with a very small actuator movement and minimal force. Its hallmark is the "snap" action that ensures fast, reliable switching even under vibration or shock.

The four most common configurations—SPST, SPDT, DPST, and DPDT—refer to the number of poles (independent circuits) and throws (output positions). Getting this wrong can lead to:

• Unexpected circuit failures

• Safety issues in automotive or medical devices

• Higher costs from over-engineering

  
  

  

Understanding Switch Pole and Throw

Before comparing switch types, we must first understand two key electrical terms:

Pole

The pole indicates how many independent circuits a switch controls.

Example:

• Single Pole (SP) → controls one circuit

• Double Pole (DP) → controls two circuits

Throw

The throw indicates how many output paths a switch can connect to.

Example:

• Single Throw (ST) → one output path

• Double Throw (DT) → two output paths

So the switch naming format becomes:

SPST vs SPDT vs DPST vs DPDT Micro Switch Comparison

The following table compares SPST, SPDT, DPST, and DPDT micro switches in terms of circuit configuration, function, cost, and typical applications.

1. SPST Micro Switch (Single Pole Single Throw)

Definition & How It Works

The SPST micro switch is the simplest and most common on/off switch. It has two terminals (Common + Normally Open or Normally Closed). When actuated, it either completes or breaks a single circuit.

Typical Terminals: C (Common) + NO or NC

Function: Basic ON/OFF control.

Pros:

• Lowest cost

• Simplest wiring

• Highest reliability for single-circuit applications

• Compact size (perfect for space-constrained designs)

Cons:

• No switching between circuits

• Limited to one function

Applications:

• Power buttons on coffee machines

• Door-open detection in refrigerators

• Safety interlocks in electric tools

• Unionwell’s G5 series basic micro switches (widely used in dishwashers and toasters)

2. SPDT Micro Switch (Single Pole Double Throw)

Definition & How It Works

An SPDT micro switch has three terminals: Common (C), Normally Open (NO), and Normally Closed (NC). The actuator routes the common terminal to either NO or NC — perfect for change-over applications.

Typical Terminals: C + NO + NC

Function: Switches between two output paths.

Pros:

• Excellent flexibility

• Can act as both normally-open and normally-closed

• Widely available in waterproof IP67 versions

• Long electrical life (often 100,000–1,000,000 cycles)

Cons:

• Slightly more complex wiring than SPST

Popular Applications:

• Reversing motor direction (e.g., car window regulators)

• HVAC mode selection (heating/cooling)

• Automotive seat adjustment and door latches

• Unionwell G303 & G304 waterproof SPDT micro switches — IP67 sealed for EV charging guns and automotive electronics

If you’re searching for a reliable SPDT micro switch, Unionwell’s subminiature G303 series is one of the most trusted options globally.

3. DPST Micro Switch (Double Pole Single Throw)

Definition & How It Works

A DPST micro switch controls two independent circuits with a single actuator. It has four terminals (two Commons + two NO or NC). Both circuits turn ON or OFF together — like two SPST switches in one housing.

Typical Terminals: 2×C + 2×NO (or NC)

Function: Simultaneous on/off of two circuits (great for safety isolation).

Pros:

• Controls two circuits at once

• Provides galvanic isolation

• Safer for AC/DC dual-voltage systems

Cons:

• Larger footprint than single-pole versions

• Higher cost than SPST

Applications:

• Dual-voltage power supplies

• Industrial motor starters

• Safety shut-off in power tools

• Unionwell G606 series offers DPST configurations for heavy-duty use

4. DPDT Micro Switch (Double Pole Double Throw)

Definition & How It Works

The most advanced — a DPDT micro switch has six terminals (2×C + 2×NO + 2×NC). It’s essentially two SPDT switches operating in sync, allowing you to reverse polarity or switch two circuits between two paths each.

Typical Terminals: 2×C + 2×NO + 2×NC

Function: Complex routing or motor reversal.

Pros:

• Maximum flexibility

• Ideal for direction control

• Can simulate change-over for stereo audio or dual signals

Cons:

• Most complex wiring

• Larger size and higher cost

Applications:

• Forward/reverse motor control (car windows, power seats)

• Polarity reversal in battery systems

• Signal routing in test equipment

• Unionwell G606, G21, and G11 DPDT micro switches — sealed versions for automotive and industrial use

In simple terms, SPST switches provide basic ON/OFF control, SPDT switches allow changeover between two circuits, while DPST and DPDT switches control two circuits simultaneously with different switching capabilities.

How to Choose the Right Micro Switch？

1. How many circuits do you need to control?  1 = SPST or SPDT; 2 = DPST or DPDT.

2. Do you need to switch between two outputs?  Choose SPDT or DPDT.

3. Voltage & current requirements? (Unionwell offers up to 250VAC/16A)

4. Environmental protection?  IP67 waterproof versions for automotive/EV (G303/G306 series).

5. Actuation force & travel? (We provide 2D/3D drawings and free samples.)

6. Certifications needed?  UL, cUL, ENEC, CE, CB, CQC — all standards at Unionwell.

Pro tip from our R&D team (20–30+ years experience): Always test with free samples in your actual environment. Over 90% of our production is fully automated, ensuring consistent quality.

Why Choose Unionwell Micro Switches

Unionwell is a professional micro switch manufacturer located in Guangdong, China, with products widely used across industries including automotive electronics, IoT devices, smart home appliances, and Industry 4.0 systems.

Key advantages include:

• ISO9001, IATF16949, ISO14001 certified production

• 100% final inspection before shipment

• automated production and testing systems

• waterproof and dustproof micro switches

• experienced R&D team with 20+ years of expertise

With strong engineering capabilities and global certifications, Unionwell provides reliable switching solutions for demanding applications.

FAQs

What is the difference between SPST and SPDT micro switches?

An SPST micro switch simply turns one circuit ON or OFF, while an SPDT micro switch can switch the circuit between two different outputs. When should I use a DPDT micro switch?

A dpdt micro switch is ideal when you need to control two circuits and switch between two paths, such as motor direction control.

Are micro switches reliable?

Yes. High-quality micro switches can reach millions of switching cycles, making them suitable for industrial and automotive applications.

Can a DPST micro switch replace two SPST switches? Yes — and it saves space and wiring.

Which type is best for automotive applications? Sealed SPDT or DPST with IATF16949 certification.