Relays Overview

What Is a Relay?

A relay is a type of switch that is controlled by an electrical circuit rather than by a human operator. These devices are among the most common of all electrical components and they come in a wide variety of designs.

Relays first came about as the result of telegraph technology. They continued to be used in communications, being employed in telephone exchanges when voice telephones became the norm.

Relays can even be used for simple computer logic. The first mechanical computers employed these devices, though they have long since been replaced by semiconductor devices that allow logic gates to trip based on electrical input alone.

Relays can be used as safety devices, cutting power under dangerous conditions. They come in all sizes, with very large relays sometimes being used to control the function of very large machinery and high-powered electrical circuits. They are inexpensive, very durable and can provide a wide range of functions within a device.

How Does a Relay Work?

The actual working parts of a relay are very simple electronic components. The most basic type of relay contains contacts for the electrical circuit to which it is attached, an armature that is linked to the contacts, a spring and an iron core with a coil.

When the coil receives electrical energy, it creates a magnetic field. This field is what powers the armature. The contacts either open or close because of this armature. There are relays available that are normally open and normally closed.

When power is removed from the device, the relay goes into the opposite condition that it was in when it was powered up. The powered state relies on the magnetic field to move the armature. In the depowered state, a spring is usually employed to return the armature to its other position.

Other components may be utilized in a relay. For example, a diode is often employed in DC relays to prevent any voltage spikes from occurring due to the change in the relay

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