The **WJM-1DG-R** is a specific model of a **Miniature Magnetic Reed Switch**, commonly used in security systems, proximity sensing, and industrial automation. It operates on the principle of magnetism to open or close an electrical circuit. --- ### 1. Key Technical Specifications Below are the typical electrical parameters for this class of reed sensor: | Parameter | Specification (Typical) | | :--- | :--- | | **Contact Type** | Form A (Normally Open - NO) | | **Switching Voltage** | Max 100V DC | | **Switching Current** | Max 0.5A | | **Contact Rating** | 10W | | **Operating Distance** | 15mm to 25mm (Gap) | | **Housing Material** | ABS Plastic (Flame Retardant) | | **Color** | White or Brown | --- ### 2. Electronic Components & Design The WJM-1DG-R consists of two primary physical parts that work together to complete the electronic function: #### A. The Reed Switch (Sensor Part) * **Hermetic Seal:** Inside the plastic housing is a glass tube filled with inert gas. * **Reeds:** Two overlapping, ferromagnetic metal blades (contacts). * **Function:** When a magnetic field is absent, the blades are separated (Open Circuit). When a magnet is brought close, the blades become magnetized and pull together (Closed Circuit). #### B. The Actuator (Magnet Part) * This is a permanent magnet encased in a matching plastic housing. * It does not require any wiring; its only job is to provide the magnetic field necessary to trigger the Reed Switch. --- ### 3. Wiring and Application Because this is a **Passive Component**, it does not require power to operate itself; it simply acts as a gate for the current in a larger circuit. * **Wiring:** Typically features two lead wires or screw terminals. * **Common Use Case:** * **Security:** Mounted on doors/windows. When the door opens, the magnet moves away, the circuit breaks, and the alarm triggers. * **Position Sensing:** Detecting the limit of a moving mechanical arm. --- ### 4. Advantages and Limitations #### **Advantages** 1. **No Standby Power:** Consumes zero electricity when idle. 2. **Durability:** The contacts are sealed, protecting them from oxidation and dust. 3. **Simplicity:** Easy to interface with Microcontrollers (like Arduino/ESP32) or standard PLC inputs. #### **Limitations** 1. **Mechanical Wear:** While long-lasting, the metal reeds will eventually fatigue after millions of cycles. 2. **Fragility:** The internal glass envelope can crack if the unit is dropped or subjected to high vibration. 3. **Current Limits:** Cannot switch high-power loads (like motors) directly; it must trigger a relay or transistor instead.