A reed relay is a kind of relay that takes the help of an electromagnet to have a control on one or even more than one reed switches. The contacts are made up of magnetic materials, furthermore, the electromagnet acts directly without requiring an armature to displace them. The contacts are sealed in a narrow, long tube made up of glass which defends them from corrosion. Several reed switches can be inserted inside the glass envelope or can be placed into a single bobbin and actuate simultaneously.

The moving parts in reed relay are lightweight and smaller than the armature based relays, thus, they can switch at a much faster speed. However, switch bounce is still present. Additionally, the requirement of operating power is not much and the value of their contact capacitance is low. Reed relay’s capacity to handle electric current is quite low but with a suitable contact material they can be optimized for “dry” switching applications. They are precisely basic, making for dependability and long life.

Basic part present in the reed relays are as follows:

• Coil – Wire is wrapped up around a core of metal. The coil causes the generation of the electromagnetic field.
• Frame – The relay has a heavy-duty frame that contains and bolsters its parts.
• Contacts – It is the conducting part present in the switch that opens or closes a circuit.
• Armature – It is the moving part of the relay. The armature closes and opens the contacts. The armature is set back to its initial position by an attached spring.

From the 1930s to 1960s a few million reed relays were utilized in Bell System electromechanical telephone exchange for memory functions. A multiple reed relay was also used where one of the reeds was carrying out memory or logic functions while the other ones were fastened with the relay. During the 1940s to the 1970s, reed relays used in the crossbar switching systems were bundled in gatherings of five. Such kind of “reed pack” was capable to keep 1 decimal digit, computed in two-out-of-five code for a simple legitimacy checking by wire spring relay logic. Such a category of latching reed relay needs consistent capacity to look after its state, which is not like magnetic latching relay i.e. later remreed (remanent reed relay) or the ferreed (ferrite and reed relay).

In the mid-1990s reed relay went out of utilization in the field of digital telephone systems (like 5ESS switch and DMS-100). But due to their fast operating time, hermetic seal, exceptionally reliable contact execution and extended lifetime, it has got its use in electronic instrumentation and automatic test equipment. It has also got several of its use in microwave switching and RF applications. The device is also utilized in equipment which utilizes their low leakage current e.g. photomultiplier detectors. Reed switches can likewise be made to withstand several kilovolts and can be utilized as high-voltage transfers instead of all the more exorbitant vacuum transfers or sulfur hexafluoride.

Some brands that make reed relays are Coto, MEDER and TE Connectivity. Check them out by going through the links as provided.

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