Magnetic Reed Switch Construction
Magnetic reed switches are electromechanical devices that open and close electrical circuits in response to magnetic fields. Their construction is critical to their functionality and reliability. The following details outline the key components and configurations of magnetic reed switches.
1. Basic Structure
A typical magnetic reed switch consists of two or three thin, flexible metal contacts known as reeds, which are housed within a hermetically sealed glass capsule. This capsule protects the internal components from environmental factors such as moisture and dust, ensuring longevity and consistent performance.
2. Types of Reed Switch Configurations
Magnetic Reed Switch Construction
Reed switches can be categorized based on their lead configurations:
Single Pull-Single Throw (Form A and Form B): In this configuration, one lead exits each end of the glass capsule.
Single Pull-Double Throw (Form C): Here, one lead exits one end while two leads exit the other end. This design allows for more complex circuit configurations.
The leads are typically made from low magnetic reluctance materials like annealed iron, which facilitates efficient magnetic flux conduction.
3. Contact Mechanism
The contact points where the reeds overlap are crucial for the operation of the switch. These contacts are often plated with ferromagnetic materials such as Rhodium or Ruthenium. This plating enhances the ability of the contacts to temporarily collect magnetic energy, allowing them to change position when exposed to a magnetic field. The design ensures that these contacts can endure millions of activations without significant wear due to their durable coatings.
4. Hermetic Sealing and Environment
The glass capsule is not only a structural component but also plays a vital role in maintaining an inert environment around the reeds. During manufacturing, the atmosphere inside the capsule is replaced with an inert gas or vacuum, which has high reluctance properties. This setup helps focus magnetic energy toward the low reluctance paths provided by the leads and contacts, enhancing performance while protecting against corrosion and contamination.
5. Functionality in Applications
Reed switches operate by either closing or opening an electrical circuit when subjected to a magnetic field:
Normally Open (NO) Configuration: In this design, the switch remains open until a magnet approaches, causing the reeds to attract each other and close the circuit.
Normally Closed (NC) Configuration: Conversely, this type maintains a closed circuit until a magnet with reversed polarity is introduced, which causes the reeds to separate and break the circuit.
This functionality makes reed switches suitable for various applications including consumer electronics (like laptops), industrial equipment, automotive systems, and medical devices.
In summary, magnetic reed switches are constructed from flexible metal reeds housed in a hermetically sealed glass capsule that provides protection from environmental factors while allowing for reliable operation through various configurations tailored for specific applications.
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