10pcs KW12-3 Roller Lever Micro Limit Switch PCB NO/NC 5A

KW12-3 Roller Lever Arm Micro Limit Switches – 10-Pack with PCB Terminals

Keep your electronics and automation projects running reliably with this 10-piece set of KW12-3 Roller Lever Micro Limit Switches. Featuring both Normally Open (NO) and Normally Closed (NC) terminals and a compact PCB-mount design, these switches deliver fast, precise actuation for a wide variety of DIY, hobby, and industrial applications. Whether you're building a 3D printer, automating a conveyor, or repairing a household appliance, these micro switches offer the dependable snap-action performance you need.

Key Features

• Model: KW12-3 Micro Limit Switch
• Switch Type: Roller Lever Arm with snap-action mechanism
• Terminals: PCB (Circuit Board) mount – Normally Open (NO) & Normally Closed (NC)
• Rated Voltage: AC 125V–250V
• Current Rating: 5A
• Operating Temperature: -40°C to 70°C
• Dimensions: 20 × 10 × 6 mm (L × W × H)
• Material: Durable plastic housing
• Quantity: 10 switches per pack

How It Works

The KW12-3 uses a snap-action reed mechanism driven by the roller lever arm. When an external mechanical force (from a cam, lever, or moving part) deflects the roller to the critical actuation point, the internal spring reed snaps instantly — making or breaking the circuit in a fraction of a second. When the force is removed, the reed returns to its original position with an equally fast reverse action. This fast-break / fast-make design ensures clean, reliable switching with minimal contact bounce.

Wide Range of Applications

These versatile micro limit switches are used across countless applications, including:

• 3D printers & CNC machines (homing & end-stop sensing)
• Computer mice & peripherals
• Automotive & communications electronics
• Gas water heaters & gas burners
• Microwave ovens & electric rice cookers
• Small home appliances & building automation
• Electric power tools & test instruments
• Floating ball equipment & fluid-level control
• Medical equipment & military-grade instruments

Package Contents

• 10 × KW12-3 Roller Lever Micro Limit Switches

Made in Mainland China.

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Electrical Safety Reference

For guidance on safe handling and use of electrical components, visit the U.S. Consumer Product Safety Commission – Electrical Safety.

Learn more: Limit switch

Frequently Asked Questions

Q: What is the difference between the Normally Open (NO) and Normally Closed (NC) terminals on the KW12-3?

A: In a micro limit switch, the Normally Open (NO) terminal completes the circuit only when the lever arm is actuated (pressed), while the Normally Closed (NC) terminal maintains a continuous circuit that is broken when the lever is actuated. This gives you flexibility to design circuits that trigger ON or OFF depending on your application's logic.

Q: Are these KW12-3 switches compatible with 3D printer end stops?

A: Yes! The KW12-3 roller lever micro limit switch is one of the most popular choices for 3D printer homing and end-stop switches. The compact 20 × 10 × 6 mm PCB-mount form factor fits standard end-stop mounts, and the snap-action mechanism provides precise, repeatable positioning — making this 10-pack a great value for builders and repair techs.

Q: What voltage and current can these micro limit switches handle?

A: Each KW12-3 switch is rated for AC 125V–250V and a maximum current of 5A. They are suitable for typical low-to-medium power switching tasks in household appliances, automation systems, and electronic equipment within these ratings.

Q: Can these switches be used in outdoor or high-temperature environments?

A: These switches are designed for an operating temperature range of -40°C to 70°C, making them suitable for a broad range of environments. However, they are not sealed or weatherproof, so for outdoor or high-humidity applications additional housing or protection is recommended.