What Is The Relay? What Does A Relay Do?

In each electronic device, no matter how big or small it is, there are small but sophisticated electronic components to make it function well. One of them is the relay. Then, what is the relay, what is the purpose of a relay, and what does a relay do? Read on to have a comprehensive understanding, as this article will cover almost all essential points! 

What Is The Relay? What Does A Relay Do?

Relays are electromechanical switches to control high-power circuits with a low-power current. They are used when a direct connection between the controlling and controlled circuits is impractical. The relay isolates the controlling circuit from the high-power controlled circuit and achieves the control process through electromagnetic action.

This way, it protects sensitive components from high voltage or current and gives more control over large systems. For example, in automotive systems, relays manage high-current starters and headlights, so small dashboard switches can control them without overheating.

How Does A Relay Function?

Relays operate through electromagnetic induction. It is the mechanism behind their switching action. Current flows through the relay's coil, which is wound around a core, for a magnetic field. It generates a force that pulls a movable armature to close or open the relay's contacts. The key is that the coil's low-current circuit can control a high-current load circuit via contacts.

For example, a normally open (NO) relay is open until the coil is activated. At this moment, the magnetic force pulls the armature to close the circuit and allow the flow of load current. This practical example may explain the question: What does a relay do?

Basically, it gives precise control over high-power circuits with electromagnetic forces to switch the load on or off. The process is important for industrial automation systems. Meanwhile, relays can control heavy machinery based on low-power controller signals.

Different Types of Relays for Specific Purposes

After learning the basics of what relays are and how a relay works, this part will focus on different types of relays and their purposes.

1. Electromechanical Relays

Electromechanical relays switch circuits using a physical coil and mechanical contacts. As mentioned before, when current flows through the coil, it creates a magnetic field to pull the armature. Such relays can handle high currents and voltages for industrial control systems. Nevertheless, contact wear and slower switching speeds might be limitations.

2. Solid State Relays

Solid-state relays use semiconductor components (transistors or thyristors) instead of moving parts to switch circuits. It gives faster switching, no contact wear, and reliability in high-frequency applications. For instance, SSRs may suit frequent on/off cycle applications, including heaters and lighting control. Yet, they may have higher on-state voltage drops and generate more heat.

Product shown in the picture: PVG612SPBF

3. Reed Relays

In a sealed glass tube, reed relays have a small coil around reed switches (ferromagnetic contacts). When the coil is energized, the magnetic field causes the reeds to contact to complete the circuit. Reed relays offer high speed, low power usage, and isolation between the coil and the switch. They benefit RF switching and telecommunications but are perfect for lower current and voltage uses.

4. Thermal Relays

Thermal relays depend on the heat generated when the electric current passes through a conductor. As current passes through a bimetallic strip, it heats up for the strip to bend and trigger a switching mechanism. It is perfect for overcurrent protection in motors. That's where they prevent overheating while disconnecting the circuit. Nonetheless, they respond slowly and can be less accurate due to ambient temperature deviations.

5. Automotive Relays

Automotive relays handle the unique electrical conditions in vehicles, including but not limited to voltage fluctuations, high temperatures, and vibration. There can be electromechanical relays, solid-state relays, micro relays, etc. They can be utilized to control headlights, horns, fuel pumps, HVAC systems, and more.

6. Safety Relays

Safety relays help guarantee machine safety while upholding control circuits in a fail-safe state. They might feature redundancy and self-checking capabilities, so the system is secure even if one component fails. Such relays are indispensable in environments where safety dominates. Their applications include emergency stop circuits and guarding systems in industrial automation.

7. Signal Relays

Signal relays are small, low-power relays that switch low-level signals, like in the millivolt or milliamp range. They can be found in communication equipment, measurement apparatus, security devices, and more.  

Conclusion

After reading this article themed around "What does a relay do?", you may have a full understanding of its importance to the reliable and efficient operation of numerous devices. AIChipLink understands these small yet critical electronic components and distributes high-quality types.

We offer a one-stop global electronic component sourcing and buying platform, helping our clients to have cheap electronic parts without sacrificing quality. Our data-driven inventory management and stable partnerships with 3000+ leading manufacturers enable AIChipLink to deliver quick and reliable services. Contact AIChipLink to get the latest information. Our professional service team can help you find what you need!