An Introduction to Relays

Introduction

Relays are essential components of a wide range of consumer, commercial, and industrial systems. They are frequently used in ordinary processes without noticing. Relays, for example, are used to control a household boiler, a television remote, or a lift. Relays were invented in 1835 to establish long-distance telegraph connections. They were then adapted for use in telephone exchanges and continue to work reliably, inconspicuously, and efficiently. In this blog you will get to know more about Relays.

What is a relay, and how does it work?

A relay is an electrically operated switch. They typically use an electromagnet (coil) to power their internal mechanical switching mechanism (contacts). When a relay contact is open, the power to a circuit is turned on when the coil is energised.

To better comprehend the issue, relays can be divided into two categories: electromechanical (EMR) and solid-state (SSR). The primary distinction is the presence or absence of moving components.

The older of the two types is electromechanical, which consists of contacts, an armature, a spring, and an electromagnet. A spring’s primary function is to hold the armature in place. When electricity is applied to the electromagnet, it exerts an attractive force on the armature, causing it to move and close a series of contacts, allowing current to flow through the circuit.

Common Relay Types

A wide range of relay types is available, each designed to meet specific application needs. It is important to note that manufacturers may use slightly different terminology for their product offers; however, here is a generalised breakdown of the main relay types:

General Purpose: These are common electromechanical relays that can control currents ranging from 2 to 30 amps and operate on AC or DC in the 12 to 230 volt range.

Signal relays handle low-power loads, which are typically less than 2 amps.
Power relays are designed to handle high-power loads while minimising heat generation and arcing.
Machine Control: These are heavy-duty, durable relays designed for big industrial applications.
Latching relays remain in their set or reset state (ON or OFF) until they receive an inverted voltage signal.
Reed relays are compact and fast.

Why are Protection Devices used in a Relay?

When a relay is turned off, the coil de-energises, resulting in a huge voltage spike. Resistors or diodes are occasionally used across the coil of a relay to prevent or lessen these spikes from returning into the control circuit and damaging sensitive components. Resistors are more durable than diodes, but not as effective at removing voltage spikes. When selecting whether or not to use protection in the control circuit, you must consider the sensitivity of the components involved.

Conclusion

Relays are employed in a variety of industries and marketplaces due to their ease of design and dependability. Relays, which began as basic components in telegraph systems and even contributed to the early creation of computers, continue to play an important role in the modern world, ensuring the safe and efficient control of electrically powered devices from a distance.

FAQs

Relays come in various types, including general-purpose, signal, power, machine control, latching, and reed relays. Each type is designed for specific applications, from low-power electronic circuits to heavy-duty industrial machinery.

When a relay coil de-energises, it can create a high voltage spike that may damage sensitive components. Protection devices such as resistors or diodes are used to suppress these spikes and ensure reliable circuit operation.