Understanding Magnetic Switches

By Jason Thompson, Updated Mar 24, 2022

A magnetic switch is an electromechanical device that toggles an electrical circuit on or off using magnetic attraction rather than a manual lever. The principle is simple: when a magnet approaches a conductive arm, the arm moves, closing or opening the circuit contacts.

Key Components

The core of a magnetic switch consists of:

• A fixed, conductive arm attached to one end.
• Two contact terminals positioned near the free end of the arm.
• A movable magnet that triggers the switch.
• Optional magnetic clamps that hold the arm in place after activation.

Common Types

There are three standard configurations, each suited to different applications:

• Normally Open (NO) Monostable: The circuit closes only while the magnet is near the arm.
• Normally Closed (NC) Monostable: The circuit opens only when the magnet is near the arm.
• Bistable (SPDT): The switch toggles between open and closed each time the magnet moves, retaining its last state even after the magnet is removed.

Operating Principles

When the magnet approaches the free end of the arm, magnetic attraction pulls the arm toward it. This movement brings the arm’s tip into contact with (or away from) the terminals, thereby closing or opening the circuit. Bistable switches incorporate magnetic clamps that secure the arm in the new position once the magnet has moved.

Typical Applications

Magnetic switches are widely used in industrial automation for safety interlocks, in home automation for motion‑activated lighting, and in automotive systems for engine control.