28 mm Reed Switch, Normally Open (NO), 2‑Pin🧲

The 28 mm Reed Switch (NO, 2‑Pin) is a compact, glass-encapsulated electromechanical component designed for low-voltage and low-current switching. It contains two ferromagnetic reeds sealed within a glass tube that close under an external magnetic field and open when the field is removed. Ideal for Arduino, Raspberry Pi, and other microcontroller-based projects, this switch is widely used in sensor applications, DIY builds, and industrial modules where reliable contact switching is required.

⚙️ Key Features

• Magnetic operation: Contacts close when a magnetic field is applied and open when it is removed.
• Normally Open (NO): This model is NO; for reference, reed switches also come in NC and SPDT (changeover) variants.
• Hermetically sealed: Glass encapsulation protects contacts from dust, moisture, and contaminants, improving reliability and durability.
• Compact and lightweight: Slim 28 mm body and approx. 2 g weight suit tight enclosures and embedded electronics.
• Fast response: High response frequency supports quick state changes in sensing applications.

📊 Technical Specifications

• Voltage Range: 3.3 V ~ 60 V DC
• Load Current (Max.): 2.5 A
• Switching Current: 1.0 A
• Max Contact Rating: 30 W
• Response Frequency: 2200 Hz
• Mechanical & Electrical Lifecycle: ≈ 100,000 operations
• Contact Resistance: 200 mΩ
• Insulation Resistance: 10 Ω
• Operating Temperature Range: −50 to 140 °C
• Length: 28 mm
• Approx. Weight: 2 g

🧰 Applications

• Sensor systems: Door/window contact sensors, bike speedometers, and magnetic field presence detection.
• Electronic devices: Keyboards, appliances, medical equipment, and general-purpose electronics components and modules.
• Automotive: Position sensing for doors, seat belts, and moving mechanisms.
• Industrial automation: Position and motion detection in machinery and equipment.
• Microcontroller projects: Simple digital inputs for Arduino, Raspberry Pi, and other microcontroller platforms.

✅ Advantages

• Electrical isolation: Hermetically sealed glass body increases reliability in harsh environments.
• Low power consumption: Magnetic actuation requires no coil drive or continuous power to hold state.
• Long lifespan: Minimal mechanical wear for extended operational life.
• High-speed switching: Millisecond response suitable for fast detection tasks.

⚠️ Limitations

• Magnetic interference: Nearby magnets or fields may cause unintended switching.
• Fragility: Glass enclosure can break under mechanical stress; handle with care.
• Limited current capacity: Not intended for high-current loads—observe 30 W max contact rating.

💡 Example Connection with Arduino

Use the reed switch as a digital input to toggle an LED. A convenient approach is to enable the internal pull-up resistor and wire the reed switch to ground (closed = LOW):

// Reed switch to Arduino example (NO type) // Wiring: // - One lead of reed switch to Arduino pin 2 // - Other lead of reed switch to GND // - LED on pin 13 (built-in on many boards)const int reedPin = 2;   // Pin connected to the reed switch const int ledPin  = 13;  // Pin connected to the LEDvoid setup() {   pinMode(reedPin, INPUT_PULLUP); // Use internal pull-up   pinMode(ledPin, OUTPUT); }void loop() {   int reedState = digitalRead(reedPin); // LOW when magnet closes the contact   if (reedState == LOW) {     digitalWrite(ledPin, HIGH); // Turn on the LED   } else {     digitalWrite(ledPin, LOW);  // Turn off the LED   } } 

Tip: For Raspberry Pi or other microcontroller boards, use a GPIO with an internal or external pull-up and treat the reed switch as a dry contact input. Consider debouncing (in software or hardware) for the most stable readings.

🔎 Summary

This 28 mm, 2‑pin, Normally Open reed switch is a versatile, reliable magnetic switch for low-voltage and low-current circuits. Its compact size, sealed construction, and fast response make it ideal for Arduino and Raspberry Pi projects, embedded systems, and industrial sensing applications. Observe the specified voltage, current, and power limits for long, trouble-free operation.