Pickering Electronics Blog

An introduction to Reed Relay basics (Part 2): The Configurations

Posted by Graham Dale on Mar 24, 2015 12:30:00 PM


Normally Closed Reeds


Normally open reed relays are by far the most common configuration of reed relay. However, normally closed relays can also be supplied where the blade is biased so it is normally closed and the application of a magnetic field opens the relay contacts.

The contact bias is created by adding an internal permanent magnet to hold the reed switch in a normally closed state. When the relay coil is energised it cancels out the magnetic field bias and the contacts open. If the coil voltage is increased substantially beyond its nominal voltage (typically greater than 1.5 times nominal) there is a risk that the contact will reclose.

Not surprisingly normally closed relays are more difficult to manufacture and have higher magnetic interaction due to the bias magnet.

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Topics: Reed Switch, Two Pole Relays, Changeover Reed, Normally Closed Relay

An introduction to Reed Relay basics (Part 1):

Posted by Graham Dale on Feb 25, 2015 10:18:44 AM

What is a Reed Relay?

Reed relays contain a reed switch, a coil for creating a magnetic field, an optional diode for handling back EMF from the coil, a package and a method of connecting to the reed switch and the coil to outside of the package. The reed switch is a simple device and relatively low cost to manufacture.


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Topics: Reed Relays, Reed Switch