Reedlülid

Reedlülid, or reed switches, are small electromechanical switches that operate under the influence of a magnetic field. They consist of two ferromagnetic reeds sealed inside a glass envelope. When a magnetic field strong enough to overcome the mechanical forces in the reeds is present, the reeds attract and come into contact, closing the circuit; removing the field allows the reeds to separate and the circuit to open. Variants can be normally open or normally closed, depending on the default position of the reeds.

Construction and design features include a glass capsule that is hermetically sealed and often filled with an inert gas to protect the contacts from corrosion and arcing. The reeds are typically made of nickel-iron alloys and are shaped to maximize contact force when actuated. In many applications, reed switches are used as part of a reed relay, where a small coil around the glass envelope creates a magnetic field to actuate the reeds without passing current through the switch itself.

Applications of reedlülid are widespread in low-power and sensing tasks. They are commonly used in door and window magnetic sensors for security systems, position and proximity sensing, counter and timing devices, and various automotive and consumer electronics applications. Their advantages include simple construction, long mechanical life, hermetic sealing, and fast response. Limitations involve sensitivity to external magnetic fields and the need for relatively low switching currents; higher-current applications often employ reed relays rather than direct reed switches.