Relay | What is a relay, its function, types and relay wiring

By October 17, 2019Article
What is a relay

What Is a Relay

If you are from the electronics field, this word must be prevalent and if you are not, let us tell you all about it!

Relays are the switches which aim at closing and opening the circuits electronically as well as electromechanically. It controls the opening and closing of the circuit contacts of an electronic circuit. When the relay contact is open (NO), the relay isn’t energize with the open contact. However, if it is closed (NC), the relay isn’t energize given the closed contact. However, when energy (electricity or charge) is supplied, the states are prone to change.

Omron Relay

Omron Relay

Relays are normally used in the control panels, manufacturing and building automation to control the power along with switching the smaller current values in a control circuit. However, the supply of amplifying effect can help control the large amperes and voltages because if low voltage is applied to the relay coil, a large voltage can be switched by the contacts.

If preventive relays are being used, it can detect overcurrent, overload, undercurrent, and reverse current to ensure the protection of electronic equipment. Last but not the least; it is used to heat the elements, switch on audible alarms, switch the starting coils, and pilots the lights.

Relay Types

In addition to the electromechanical and electromagnetic relay, there is a wide variety of relays with different working principles; principles of operation and polarity.


  • Electrothermal Relay – When two different material gets in contact, bimetallic strip is formed, and when it is energized, it bends. This bending allows the users to make contact connections
  • Electromechanical Relay – When different mechanical parts are connected on the basis of the electromagnet, contact connection is established
  • Solid State Relay –This relay uses semiconductor devices to make a connection to ensure the effectiveness, efficiency, and easiness of the switching speed. This is commonly used for two reasons; faster-switching process and durability
  • Hybrid Relay – It is the name given to the solid-state and electromechanical relays

Relay Types As Per The Polarity

  • Polarized Relay – These relays are identical to electromechanical relays except for the presence of electromagnet and a permanent magnet. With this relay, the armature movement is based on the input polarity applied to the coal and is commonly applicable in telegraphical purposes
  • Non-polarized Relay – There are no polarities in this relay, and it executes no change with the alteration of the input signal

We all are aware of the TV remotes on which we can press one button to make a function, relays work similarly to that. Relays are used to eliminate the direct link of users with electronic equipment to protect them for expected high voltages.  If the vast industries are focused, they are using the bigger capacity relays to optimize the motors and pumps operation.

The common purpose of relays can be understood by analyzing the headlight turn on. The headlight switching button can be found on the car dashboard, and if moved, they supply the small value of current to the coil which results in contactor switching on. Then, relay comes into action by controlling the high power load (headlights). There are many other common examples of relays from our daily life.

Everyone has a fridge at their home and relays control the equipment responsible for working and production of cold temperature. Traffic lights are another application of relays where they are used as the switching component. The movement and direction of automatic garage doors are also utilizing the relays for optimal switching contacts.

It is safe to state that relays are responsible for energizing the electronic equipment and work on their functioning to ensure the optimal operation. These have eased our lives by bringing in automation factors along with the safe and smooth running of electronic equipment. This means that there are no threats involved regarding the high voltage as there will be no contact at the time of an electronic breakdown.

Relay Function

We have added the relay diagram in the section below to ensure the clear understanding of relay wiring and relay circuits along with their working.


What is relay function

What is relay function

The diagram sheds focus on the internal section of the relay in the circuit. There is an iron core delimited with the control coin. The power source connects with electromagnet through load contacts and a control switch. When energy is supply to the circuit through the control coil, magnetic fields intensifies given the commencement of energizing. This way, upper contact arms gets attracted by the lower fixed arm which closes the contacts leading to the short circuit. However, if the relay was de-energized, an open circuit is created with the opposite movement of the contact.

Once the coil current goes off, a movable armature is force back to the initial position, and the force is equal to half of the magnetic force and electric strength. The main reasons behind this force include gravity and spring.

The relays perform two basic functions, such as high voltage application and low voltage application. In the case of high voltage, arcing is reduce while in the low voltage applications, overall circuit noise is reduce to a minimum.

Related Topic:

Relay: Structure of Relays and Operating Principles

Relay Wiring

 These relay diagrams focus on the wiring configuration in a 2-pole relay circuit. One is the square, and the other one is round, but their functioning is similar to each other. The coil wire will connect to pin 2 and pin seven on the socket for the wiring.

In the diagram given below, L1 (hot) goes to the closed switch which signifies the current application until the switch is open. The L1 will be hot to the START switch, and when the switch is pressed, L1 leads to Master Control Ray and supply the charge. 

Relay Wiring

Relay Wiring


Now, release the START button, and the current will start flowing around the open START switch. To switch off the light, we press on the STOP button, and it will de-energize the coil. Once the STOP button is let off, the START button will depressed, and this is what relay circuit is all about!

If you are in need of an Omron relay, you can get in touch with us at Electgo to buy Omron relays at relatively lower prices. If you sign in to our website, you will be provided with a discount. We are the best choice because we have an in-house team of engineers who are best at providing technical support to our clients. Once you buy the relay from us, we will also provide the relay datasheet for the provision of information.


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