Characteristics of a Relay

Introduction to Relays

What is a relay? An innovative device dating back to 1835, created by the American physicist Joseph Henry. It works like an electric switch which, through an electrical impulse, allows you to close or open a circuit.

Main Components of the Relay

The relay is made up of three fundamental parts:

• Coil
• Again
• Contacts

Coil Types

There are two main types of coils in relays:

• Simple - characterized by a single winding that manages multiple contacts.
• Multiple - has three windings, which can be activated by the same signal or by different signals.

Types of Contacts

In relays, contacts can be classified into:

• NA (Normally Open) - closes only when the coil is energized.
• NC (Normally Closed) - opens only when the coil is energized.
• Exchange contact - acts as a diverter.

Different Types of Relays

Based on switching, relays are categorized into:

• Neutral - the change of contacts is independent of the direction of excitation of the coil.
• Polarized - the change of contacts varies according to the direction of excitation of the coil.

Important Classifications

Some crucial distinctions to consider when choosing a relay include:

• Monostable - where the position of the contacts changes momentarily with excitation.
• Bistable - the contacts maintain their position until a new impulse is provided.
• Timed - with contacts that change position after a certain set period of time.

Relay - Features and Functionality

Monostable (or release) model

The monostable model is characterized by the presence of a single coil inside. The current, acting on this coil, allows the relay to power what is connected to it, such as a series of lights. This happens because inside the relay there are contacts which, through the use of a button, move from one circuit to another, returning to the previous stage once the impulse has ceased.

• When is it advisable to use a monostable device? It is ideal for turning on several light points within a room using a single button or switch.

Bistable relay (or switch)

The bistable is distinguished by having two coils. This type of relay, when energized by current, changes state in the circuit, operating the connected equipment. Unlike monostable models, once the power supply stops, the circuit remains in the state set by the last pulse, thanks to the use of the second coil.

• When is it advisable to use a bistable one? It is the perfect solution for those who want to control a light point from multiple switches within the same area.

Timed model

Timed or delayed devices activate or deactivate after a specific amount of time after the button has been pressed. They therefore offer the possibility of managing the switching on or off of devices at specific times.

• When is it advisable to use a timed model? They are ideally used to program the turning off of lights in areas such as buildings, villa driveways, or garages.