Relays: Different Types and Applications

Historically, the relay has been used as a means to transmit and receive information. Its earliest application was for contact through Morse code, an encoded system of telecommunication wherein letters and numbers are communicated through a standardized set of signals. Relays have many different classifications, but a standard relay is typically made of electromagnets and operates as a switch. The principal function of a relay is to open or close circuits electromechanically. They are more commonly used to control smaller currents and are not usually found in power consuming devices aside from small motors.

Electromagnetic relays are designed and constructed using mechanical parts including an electromagnet, movable armature, contacts, yoke, and a spring. The electromagnet, though it is a metal, has no magnetic properties until it is converted to a magnet via electrical signals. This is because currents passing through conductors take on the properties of a magnet. The electromagnet is wound with a copper wire and, when given sufficient power, acts as a magnet, attracting the surrounding parts and enabling the relay to function. Aside from electromagnetic, there are four other types of relay. They are:

Electrothermal: A relay made when two different materials are combined and formed into a bimetallic strip. When energized, the strip bends, connecting with the relay contacts.

Electromechanical: This relay is similar to the electromagnetic relay, but additional mechanical parts are the driving force, rather than magnetic power.

Solid State: These relays use semiconductor devices rather than mechanical parts, making device switching both faster and easier. An additional advantage of a solid state relay is its lifespan.

Hybrid Relay: As the name suggests, a hybrid relay is a combination of mechanical and solid state relays.

The differing types of relays provide a long list of applications. In addition to their use in electrical circuits, they are found in computer circuits, often performing the mathematical functions they feature. In automatic stabilizers, relays sense an increase or decrease in voltage and help control the circuit load. Relays are also used in televisions, traffic signal controllers, and temperature controllers to turn them on and off.

At Complete Sourcing Solutions, owned and operated by ASAP Semiconductor, we can help you find relays for the aerospace, civil aviation, and defense industries. We’re always available and ready to help you find all the parts and equipment you need, 24/7-365. For a quick and competitive quote, email us at or call us at 1-503-374-0340.


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