relay, The relay is an important electronic and electrical component for use in many different applications. such as electronic circuits, and electrical control panels.

Where the relay is available in a variety of types, shapes and sizes, commensurate with the nature of use. Such as the effort of the relay and the number of points of contact.

Follow this article with us to learn about the types of relays and how they work and examine them.

Relay working principle

The principle of the work of the relay depends on the delivery of electric current through contact points, when feeding its coil with a direct current or an alternating current; The main benefit of this process is to operate a high-powered load by feeding the relay coil with a small current, or by giving a signal from the PLC, or a signal from electronic boards…etc.

relay components

The relay consists of several parts:

1. copper coil.
2. invert the file.
3. Points of contact ( normally opened , normally closed , and common).
4. spring.
5. External terminals.

Types of relay points and their composition

1- A switch with one input and one output (SPST):

This type has one current input and one output point. It is used to connect or disconnect a single line or path in a circuit.

2- A switch with one input and two outputs (SPDT):

This type has a common input point (C) and two outputs, one closed and the other open.

3- A switch with two inputs and one output for each input (DPST):

4- A switch with two inputs and two outputs (DPDT):

This type has two inputs and each input has two outputs. Where (Throw) is the number of outputs per pole.

Types of relay

1- Reed relay

Its working principle is based on magnetic cutting, Its contact points are connected when a magnet is near it.

2- Latching relay

Its principle of operation is based on continuous conduction when pressed.

3- Contactor relay

It is similar to the idea of the work of the relay, but it is used to feed large loads, Like electric motors.

4- Mercury-Wetted relay

It conducts and separates by a drop of mercury inside a tube, If the connection is in a vertical position, In the case of separation be in a horizontal position.

5- Solid-state relay

Does not depend on conduction through mechanical parts and magnetic coil, Rather, it depends on the connection through an electronic board designed in a certain way to perform the function of the relay. This type is more expensive compared to mechanical relays.

6- Overload protection relays

It is used to protect loads from rising and falling electric current.

Different shapes and types of relays

Choosing the right relay

The nature of the choice of relay depends on several factors, namely:

1. value and type of relay coil, Available in (6v,9v,12v,15v,24v,36v,48v).
2. Maximum contact current, It ranges from 1A-60A.
3. The number and type of contact points, Such as (DPDT, SPST, DPST, SPDT).

How to check the relay

1- Put the red probe into the ohm port, and the black probe in the common port (COM).

2- Turn on the multimeter.

3- Set the increment knob to the ohm symbol, And choose the conductivity symbol by pressing the switch button, if any.

* Placing the red probe on either end of the joint, And the black probe is on the closed point (NC), and we note the following :

If a read appears, or hear a buzzing, Indicates that the contacts are in a connected state, and this is normal and healthy if the coil is not being fed.

When feeding its coil, it must be ensured that the relay point (NC) is connected to the joint.

4- Keeping the red probe as it is, We move the black probe on the open point (NO), and note the following :

• If no read appears, or not hear a buzzing, This indicates that the contact points are in a state of separation, and this is normal and sound in the event that it is not fed to its coil.

• When feeding his coil, the relay points (NO) must be connected to the subscriber.