Reed switch

1123 palavras 5 páginas
Reed switch
From Wikipedia, the free encyclopedia

Reed relay and reed switches

Showing the contacts clearly
The reed switch is an electrical switch operated by an applied magnetic field. It was invented at Bell Telephone Laboratories in 1936 by W. B. Ellwood. It consists of a pair of contacts on ferrous metal reeds in a hermetically sealed glass envelope. The contacts may be normally open, closing when a magnetic field is present, or normally closed and opening when a magnetic field is applied. The switch may be actuated by a coil, making a reed relay,[1] or by bringing a magnet near to the switch. Once the magnet is pulled away from the switch, the reed switch will go back to its original position.
An example of a reed switch's application is to detect the opening of a door, when used as a proximity switch for a burglar alarm.
Contents [hide]
1 Description
2 Uses
2.1 Reed relays
2.2 Magnetic sensors
3 Further reading
4 External articles and references
[edit]Description

The reed switch contains a pair (or more) of magnetizable, flexible, metal reeds whose end portions are separated by a small gap when the switch is open. The reeds are hermetically sealed in opposite ends of a tubular glass envelope.

Reed switch diagrams from Ellwood's patent, U.S. Patent 2,264,746, Electromagnetic switch
A magnetic field (from an electromagnet or a permanent magnet) will cause the reeds to come together, thus completing an electrical circuit. The stiffness of the reeds causes them to separate, and open the circuit, when the magnetic field ceases. Another configuration contains a non-ferrous normally-closed contact that opens when the ferrous normally-open contact closes. Good electrical contact is assured by plating a thin layer of non-ferrous precious metal over the flat contact portions of the reeds; low-resistivity silver is more suitable than corrosion-resistant gold in the sealed envelope. There are also versions of reed switches with mercury

Relacionados

  • Reed switch
    3122 palavras | 13 páginas
  • Motor elétrico usando reed-switch
    1475 palavras | 6 páginas
  • Reed swet
    1047 palavras | 5 páginas
  • sensores
    1410 palavras | 6 páginas
  • Motores elétricos - montando um caseiro
    1303 palavras | 6 páginas
  • APS REED atualizada
    788 palavras | 4 páginas
  • Descri O Do Trabalho N2 Circuitos L Gicos
    408 palavras | 2 páginas
  • motor experimental
    842 palavras | 4 páginas
  • Estudante Engenharia
    2001 palavras | 9 páginas
  • Boia magnetica
    872 palavras | 4 páginas