MC-38 Magnetic Door Window Sensor – Normally Closed (NC) Wired Reed Switch Alarm Contact

A reliable MC-38 magnetic door/window sensor designed for security systems and automation projects. This wired magnetic reed switch detects the opening and closing of doors or windows, making it ideal for alarm systems, smart home setups, and DIY electronics.

Configured as a Normally Closed (NC) switch, the circuit remains closed when the magnet is nearby and opens when the door or window is moved.

Key features

• Normally Closed (NC) operation
• Reliable magnetic reed switch sensing
• Simple 2-wire connection
• Compact and easy to install
• Suitable for recessed or surface mounting (depending on installation)
• Durable plastic housing

How it works

The sensor consists of two parts: a reed switch and a magnet. When the magnet is close to the switch (door/window closed), the circuit is complete. When the magnet moves away (door/window open), the circuit breaks, triggering an alarm or signal.

Wiring

• 2 wires – Connect in series with your alarm system or input circuit

Tip: Use a pull-up or pull-down resistor when connecting to a microcontroller input.

Specifications

Common applications

• Home security alarm systems
• Door and window monitoring
• Smart home automation
• Arduino and ESP32 projects
• Access control systems
• Industrial safety switches

Important notes

• Ensure proper alignment between the magnet and switch for reliable operation
• Designed for low-voltage signal circuits
• Mount securely to prevent false triggering

Tip: Normally Closed (NC) sensors are commonly used in security systems because they can detect both opening and wire tampering.