What Is a Relay?

What Is a Relay?

Relays are indispensable to most modern electrical devices. They’re essential for converting feeble electrical inputs into current levels that can operate motors, lights, and many other electronic circuits. The relay is a clever device that takes low-voltage, small-capacity control signals and transforms them into higher-current outputs using the power of electromagnetic force.

Relay devices are found in almost any appliance or piece of equipment that uses electricity in the home, workplace, or car. They’re even used to control the flow of electric current in a transmission line. While it’s not a device that everyone has or knows much about, it is a very important tool in the field of electrical engineering.

To fully understand what a relay does, you have to know how it works. There are different types of relays, such as solid-state and electromagnetic. The type of relay you need depends on the application and how much current and voltage it must handle. Also, there are other features that you should look for such as the coil type, contact configuration, and response time.

Most relays come in a semi flush-mounting draw out case. This makes it easy for installers to plug them in and connect them to the wires of an electrical system.

The inside of a relay consists of an electromagnet coil and movable contacts. The coil is powered by a low-voltage, AC or DC current. This current activates the magnetic force that carries the armature or movable contact(s) and closes or opens them. When the current stops flowing through the coil, the armature or contact(s) are returned by a spring or other means to their original position.

There are many types of relays available, each with its own specifications. These include the number of poles and throws, which determine how many different circuit connections a single relay can control. Some relays are designed to handle high-voltage applications, while others are rated for low-voltage use.

If you’re going to install a relay, you need to know how to test it. Fortunately, testing the integrity of a relay is quite simple with a multimeter. Set your multimeter to the continuity or resistance mode and probe the point where the relay’s circuits enter and exit. If the multimeter detects voltage, you can proceed with further testing.

Once you’ve identified the faulty relay, you can begin troubleshooting. If you find that the contacts are not engaging properly, you can inspect the relay for a mechanical fault. You can also check the contact positions with a multimeter by applying the rated coil voltage and checking for continuity between the "coil," "C," and "NO" terminals. The results should be low or infinite, indicating closed and open contacts respectively.