Magnetic, Reed Switches

A reed switch (also known as a reed switch) is an electrical switch operated by a magnetic field. It consists of two soft magnetic metal reed contacts enclosed in a glass tube. In the absence of a magnetic field, the contacts remain open. When a magnetic field is present, the reeds become magnetized and close, completing the circuit. It was invented by Walter Elwood of Bell Labs in 1936.

 

1. What are the Working Principles of Magnetic, Reed Switches?

Normally Open Mode: The contacts close when a magnetic field is present and open when it is removed.

 

Normally Closed Mode: The contacts open when a magnetic field is present and close when it is removed.

 

Maintained Mode (Bistable): A change in magnetic field polarity triggers a state change and remains in that state when the magnetic field is removed.

 

2. What are the Applications of Magnetic, Reed Switches?

Sensors: Used for counting and limit switches (such as bicycle odometers).

 

Security: Door and window alarms.

 

Industrial Safety: Coded reed switches are used to monitor the position of protective devices (requires use with safety monitors).

 

3. What are the Advantages and Disadvantages of Magnetic, Reed Switches?

Advantages: Small size, long life, and fast response.

 

Disadvantages: Low current capacity and complex fault detection.

 

4. Technological Developments of Magnetic, Reed Switches

Ultra-small reed switches (glass tube inner diameter 0.8–1.0 mm) have entered mass production and are suitable for use in microelectronics, although rated current and voltage parameters must be reduced.