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How To Connect A Relay Efficiently

Various electrical devices utilize relays. You can find relays in everyday household items such as your lamps. The automotive industry also uses relays to make a car function properly. When it comes to relays, you don't need to be a professional. To prevent harming yourself or damaging your devices, you should know how to connect a relay correctly. 

It can become frustrating at times when you are unsure of how something works. In this article, we'll examine basic relays, what they do, how they work, and how you can connect them to a power source. 


1. How Does A Relay Work?


A diagram of how a relay works


(A diagram of how a relay works )


Relays are switch devices that allow an electrical circuit to be opened and closed. They control one electrical circuit by opening and closing contacts in another circuit. They switch lower currents in a control circuit and are generally not used to control power-consuming devices except perhaps for small motors. Current flows through the relay coil, and a magnetic field is generated. This field attracts a lever and changes the switch contacts.

This video will show you how a relay works when connected. 


2. Different Types of Relays


Here, we are going to break down the different types of relays that you can get. 


  • Relays, both Electromechanical and Reed


Electromechanical relays operate electrically, which helps to isolate circuits or batteries. These relays are helpful to the power management of the control systems because they help control energy-consuming loads such as resistive and inductive loads. 


Reed relays control one or more reed switches. They are sealed in a long, narrow glass tube so that the contacts are safe from corrosion. You should use this relay for switching applications that require low and stable contact resistance. When you supply power to a reed relay coil, you create a magnetic field. This field causes the relay to shift and the contacts to close. 


A pair of relays

A pair of relays


  • PCB Mount Solid State Relays


Solid State refers to a class of switches based on semiconductor devices. The relays mount onto Printed Circuit Boards. You will often find a solid-state relay in commercial and industrial applications such as food equipment.


Four solid state relay modules

Four solid state relay modules


  • Switches that are unsealed, sealed, or failsafe to flux


An unsealed relay lacks any protection against flux or cleaning solvents penetrating the relay housing. First, you must disconnect the terminals from the PCB surface to mount an unsealed relay. 

Neither flux nor cleaning solutions can damage the housing of sealed relays. You will find a soldered flux protection relay on a PCB, and it will not be clean by immersion techniques. 


Using protection relay and medium pressure switchgear

Using protection relay and medium pressure switchgear


3. What You Need To Know About Relay Pin Terminals 


Keep in mind; four-pin relays control just one circuit, whereas five-pin relays control two circuits simultaneously. 


3.1 What is the polarity and tension of the relay?


When it comes to Electromechanical and Solid-state relays, you must consider the polarity for the relays and the nominal voltage. 

In other words, you need to check the voltage of the relay. If you do not do this, you can burn out the relay, and it will not work. You might find that some relays have a wide range when it comes to voltage. You might find that some AC circuits can handle up to 250V. 


3.2 Relay Terminals: How Are They Numbered?


Below, we will share with you how relay terminal numbers work according to the relay type. 


Electrochemical relay


There is often a printed diagram with A1+ & A2- painted on it, which can be found on the side of the relay alongside two segments joining a square.


Reed relay


Reed often relies only on have two wires or pins attached. They are those of the output or power circuit. There are no coils or electronics to this relay which means they have no numbers. 


Solid-state relay


You will often find the numbers 4- and 3+ on a solid-state relay. When there is a three-phase circuit, you can also find 1 ~ and 2 ~.  


4. Typical Relay Connection Method


Electrical Relay

Electrical Relay


By now, you should have a better understanding of which relay you own. Below is a primary method of how you can connect a relay. This method works for 9V relay, 5-6V relay, Automotive relay, and more.


Step one


Turn your relay on the side so that you can see the drawing on the side. The picture will give you the numbers for the relay coil. Check and make sure you know your power requirements.


Step two


Electrical Switch Relay connected to the correct base and relay terminal

Electrical Switch Relay connected to the correct base and relay terminal


If your relay requires a base, ensure that you get the right one.  


Step three


Get your wire and place your Positive in your A1 slot and the negative in the A2. Ensure the wire placement is on the correct relay terminal. You can solder your wires carefully to the correct terminal pin. You will often find that your GPIO pins will operate the control circuit.  


Step Four


Relay protection test of the modern electrical device

Relay protection test of the modern electrical device


Turn your power supply on and ensure that your relay is working. If it is not turning on, you could have a short in your wiring; you have not connected your wires correctly. 


Step Five


You can then connect your relay to the object that you want to power up. Connect a relay terminal to an open slot in your relay to an open slot in your base. Remember, you can find which slots are open circuits and which ones are closed by reading your diagram. The output you will then place in a closed circuit slot.


Step six


Circuit symbols of relays


Circuit symbols of relays


Place your relay into the base. The base will allow you to use your relay to switch on your object, such as a light bulb. Now, your relay will work as the on-off switch for your power circuit. If you are not using your relay, the control switch should handle the full current of the installed lightbulb. Keep your circuit design simple. 

5. FAQs about Connecting Relays 


What numbering has the base or base?


The numbering that shows in the relay will also show in the connection base. Space has been provided in the control cabins to expand the relays in the future.

What is the identification of a relay contact according to his group?


The first digit indicates the group, and the second digit indicates the contact. For example:
11- Inverter Contact
12- Closed Contact
14-Open Contact

When is a relay an open or closed contact circuit?


Usually, when a relay is at rest, the circuit is closed by pushing the current through the moving plate connected by the contacts. This contact is known as closed contact. Open contact is when the stationed contact separates from the contact point that moves. 


Is there any limit to the number of "groups of contacts" an electromechanical relay has?


You can quickly tell how many groups of contacts your electromechanical relay has. Electromechanical relays have either two or three groups of contacts depending on which type you buy. 


Should we do a first activation test when connecting a relay?


You should do a connection test before you carry on with your installation. It will ensure that your relay is working correctly and help you avoid burnouts. 




Different voltages can be connected using a relay. A relay allows you to switch your circuits on and off without any hassle. These electrical devices come in various types, which help send power to different electrical circuits through a relay coil. As soon as you understand what relay you need, you will connect it with ease. 

Now, you have a better understanding of how to connect a relay correctly and efficiently. You can contact us at any time.