What are Magnetic, Reed Switches?
When the switch is open, a pair of flexible, magnetizable metal reeds with their end sections separated by a tiny space is within the most typical form of the reed switch. The reeds are enclosed in a glass tube that is hermetically sealed. One flexible reed in a different kind of reed switch alternates between a normally fixed open and normally closed contact. The flexible reed's spring force closes the non-magnetic, normally closed contact, which is ordinarily closed. Although multiple-pole reed switches are conceivable, assemblies of single-pole reed switches are more frequently employed in multi-pole applications.
How do magnetic switches work?
An electrical switch known as a magnetic reed switch creates or breaks contact when a magnetic field is present. Applications include circumstances when it is undesirable or impractical for moving elements to make direct contact with the switch, such as in hazardous locations, while submerged in liquids, or where repeated contact with a mechanical switch would cause unwanted wear. The switch typically closes when the magnetic field is withdrawn but stays activated as long as a powerful enough magnetic field is present.
Typical applications
Reed relays
A reed relay is made up of one or more reed switches that are housed inside an electromagnetic coil. When operating currents are low, reed relays are employed because they have a fast-working speed, good performance with extremely low currents that can't be switched reliably by conventional contacts, great reliability, and a long lifespan. In the 1970s and 1980s, telephone exchanges employed millions of relays. In the British TXE family of telephone exchanges, they were specifically used for switching. The reed contacts are surrounded by an inert environment, which prevents oxidation from affecting the contact resistance.
Magnetic sensors
Mechanical systems frequently employ reed switches with magnet-activated proximity sensors. Examples include tamper-proofing techniques and door and window sensors in burglar alarm systems. When the lid is closed on a laptop, Reed switches have been used to put the device into sleep or hibernation mode. When a magnet on a bicycle wheel passes by a speed sensor, it commonly uses a reed switch to momentarily trigger the sensor. The keyboards for computer terminals utilize reed. In the past, keys contained magnets and a reed switch that were activated by pushing the key.
