MC-38A Wired Door Window Magnetic Sensor Switch NC NO

The MC-38A Wired Magnetic Door & Window Sensor Switch is a compact, reliable component for home security and automation systems. With both Normally Open (NO) and Normally Closed (NC) reed switch options available, this sensor detects whether a door or window is open or closed by sensing the proximity of its paired magnet — making it an essential building block for DIY alarm systems, smart home setups, and access-monitoring projects.

Its slim plastic housing (27 × 14 × 8 mm) fits discreetly on wooden doors, window frames, cabinets, and more. Installation is straightforward via screws or double-sided tape, and each set includes a 350 mm wired lead for easy connection to your alarm panel or microcontroller.

Key Features

• NC & NO Options: Choose Normally Closed (opens when magnet moves away) or Normally Open (closes when magnet is near) to suit your circuit design
• Compact Size: 27 × 14 × 8 mm — fits neatly on doors, windows, cabinets, and drawers
• Easy Installation: Mount with screws or double-sided tape (SMD-style installation)
• 350 mm Wire Lead: Pre-wired for quick integration into alarm panels and controllers
• Durable Plastic Housing: Lightweight yet sturdy for long-term everyday use
• Versatile Application: Ideal for wooden doors, windows, gates, and enclosures
• Available in 2 Colors: Choose the finish that best blends with your interior
• Package Includes: 1 complete sensor set (magnet + switch unit)

How It Works

A reed switch sensor operates using a small internal metal reed. When the paired magnet is brought close, the magnetic field causes the reed contacts to change state. On a Normally Open (NO) switch, the circuit closes when the magnet is nearby (door/window closed) and opens when the magnet moves away (door/window open). On a Normally Closed (NC) switch, the opposite is true — the circuit is closed by default and opens when the magnet is removed. This simple and dependable mechanism is widely used in residential and commercial security systems.

Specifications

• Model: MC-38A
• Material: Plastic
• Dimensions: 27 × 14 × 8 mm
• Wire Length: 350 mm
• Switch Output: Normally Open (NO) / Normally Closed (NC)
• Installation: Screws or double-sided tape
• Recommended Surfaces: Wooden doors, windows
• Colors Available: 2 options

Ideal For

• DIY home alarm and security systems
• Smart home automation projects
• Arduino, Raspberry Pi, and microcontroller builds
• Door/window open-close monitoring
• Cabinet and drawer access detection

For guidance on home security best practices, visit the Cybersecurity & Infrastructure Security Agency or refer to the U.S. Consumer Product Safety Commission (CPSC) for consumer product safety information.

Frequently Asked Questions

Q: What is the MC-38A Wired Magnetic Door & Window Sensor Switch used for?

A: The MC-38A is a wired magnetic reed switch sensor designed for home security and automation systems. It detects when a door or window is opened or closed by sensing the proximity of a paired magnet. It can be wired into alarm panels, microcontrollers (such as Arduino), or smart home hubs to trigger alerts or automate actions when an entry point is accessed.

Q: What is the difference between NC (Normally Closed) and NO (Normally Open) reed switches?

A: A Normally Open (NO) reed switch has contacts that remain open (circuit off) when no magnet is nearby. When the magnet comes close — such as when a door is shut — the contacts close, completing the circuit. A Normally Closed (NC) reed switch works in reverse: the contacts are closed by default and open when the magnet is brought near. The correct type depends on your alarm system or circuit design requirements.

Q: How do I install the MC-38A door/window sensor?

A: Installation is simple. Mount the sensor body on the door or window frame, and attach the magnet to the moving door or window itself. Use the provided screw holes or double-sided tape (SMD-style mounting). Align the two pieces so they are within close range when the door/window is closed. Connect the 350 mm wire lead to your alarm panel or controller. No special tools are required.

Q: What surfaces is the MC-38A sensor compatible with?

A: The MC-38A is recommended for wooden doors and windows, making it well-suited for most residential interior and exterior doors, window frames, and cabinet enclosures. Its compact 27 × 14 × 8 mm size ensures it fits discreetly on most surfaces.