Reed Switch
🧲 Reed Switch
📌 Overview
A Reed Switch is a magnetically operated switch that opens or closes in the presence of a magnetic field.
👉 Commonly used in:
🚪 Door/window sensors
🚗 Speed detection
🤖 Robotics
🔐 Security systems
🧠 Working Principle
Inside the switch → two thin ferromagnetic metal reeds sealed in a glass tube
When a magnet comes close:
Reeds attract each other → circuit closes (ON)
When magnet moves away:
Reeds separate → circuit opens (OFF)
👉 Based on magnetic attraction (no power needed to operate)
📊 Infographic Summary
┌──────────────────────────────┐
│ 🧲 REED SWITCH │
├──────────────────────────────┤
│ 🎯 Function: Magnetic switch │
│ ⚡ Power: Not required │
│ 🔌 Output: Digital (ON/OFF) │
│ 📦 Type: Normally Open/Closed│
│ 🔁 Operation: Contact-based │
│ 🧠 Trigger: Magnetic field │
└──────────────────────────────┘
🔌 Basic Connection
┌──────────────┐
│ Reed Switch │
├──────────────┤
│ Terminal 1
│ Terminal 2
└──────────────┘
👉 Works like a simple switch
👉 Connect in series with circuit or microcontroller input
⚙️ Types of Reed Switch
🔓 Normally Open (NO)
OFF by default, turns ON near magnet
🔒 Normally Closed (NC)
ON by default, turns OFF near magnet
🔁 Changeover (SPDT)
Switches between two contacts
🌟 Key Features
🧲 Magnetic field detection
⚡ No external power required
🔧 Simple and reliable
📦 Compact and sealed
🔋 Low power consumption
🧪 Applications
🚪 Door/window alarm systems
🚲 Bicycle speedometer
🚗 Wheel rotation sensing
🤖 Robotics limit switches
💡 Proximity detection
🧰 Industrial automation
🔗 Interfacing
Compatible with:
🔵 Arduino
📡 ESP32 / ESP8266
🍓 Raspberry Pi
👉 Connect one terminal to GND, other to digital input (use pull-up resistor)
🔄 Working Example
👉 Door Sensor System:
Door closed → magnet near → switch ON
Door open → magnet away → switch OFF → alarm triggered
⚠️ Important Notes
⚠️ Fragile (glass enclosure)
⚠️ Limited switching current
⚠️ Can wear out with very frequent switching
⚠️ Sensitive to strong magnetic fields
🆚 Reed Switch vs Hall Effect Sensor
| Feature | Reed Switch | Hall Sensor |
|---|---|---|
| Output | Mechanical ON/OFF | Electronic signal |
| Durability | Moderate | High |
| Speed | Slower | Faster |
| Power Requirement | No | Yes |
💡 Pro Tip
Place magnet very close (few mm) for reliable operation
Use with pull-up resistor to avoid floating signals
👉 Perfect for simple, low-cost magnetic detection projects
