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Introduction to electronic relay – an electronic control device

Electric relay offers a dependable and effective way to automate circuits, safeguard equipment, and isolate control circuits from high-power components. In-depth discussion of the use of electronic relays, types that are available, their principles of operation, applications, distinctions from switches, connection techniques, components, and testing procedures will be covered in this article.

We hope that after reading this article, you will gain significant and actionable knowledge regarding electric relays which you can use in the world of electronics intelligently.

Table of Contents

What is an electronic relay used for

Electric relay is a useful device meant for regulating the flow of electric current in a circuit. It performs the function of a switch, but an electrical signal rather than a mechanical action control it. This device finds its use in a number of applications aiming to automate system or device control. Moreover, this device is also used for offering electrical protection and isolating control circuits from high-power circuits.

What is an electronic relay used for and its types
What is an electronic relay used for and its types

How many types of electronic relays are there

Electronic relays come in a variety of forms, including:

● Electromechanical Relays: For these relays to function, an electromagnetic coil is used to switch them off and on.
● Solid-State Relays (SSRs): SSRs switch the current flow using semiconductor components like transistors and optocouplers. They offer quick switching and good reliability with no moving parts.
● Reed Relays: In these relays, metal reeds are used but make sure that those reeds are magnetically sensitive and housed in glass tubes. The reeds make contact when a magnetic field is applied, allowing current to flow.
● Time Delay Relays: Relays with a time delay before switching the contacts are called time delay relays, and they are beneficial in applications where a delay is needed before starting or terminating a process.

What are the applications of electronic relays

Although electronic relays find applications in various industries and systems, the most important used of electric relays are:

● Industrial automation and control systems
● Power generation and distribution
● Automotive systems
● Telecommunications
● Home automation

How does an electronic relay work

For the electronic relay to work, the witching action of an electronic relay is controlled by an electromagnet. When electric current flows through the coil it produces a magnetic field which results in attracting or repelling a movable contact. The electrical connection is made or broken by this contact, which is mechanically connected to the circuit’s power terminals and adjusts its position accordingly.

What is the difference between a switch and a relay

The method of operation is the primary distinction between a switch and a relay. The most common way to activate a switch is manually, either by a person physically moving a lever or by a machine. A relay is a switch that gets switched on and off automatically and is electrically controlled. An electrical signal, which may be produced by a switch or another device, controls the relay.

What is the difference between a power relay and an electronic relay

Both “power relay” and “electronic relay” have valid uses and are not mutually exclusive. However, a relay that is made to perform high-power or high-voltage tasks, such as managing motors, transformers, or large electrical loads, is referred to as a power relay in general. On the other hand, a solid-state relay (SSR) that uses semiconductor devices for switching and control is referred to as an electronic relay since it is controlled by electronic control signals.

How is a relay connected to a circuit

A relay’s input and output terminals are commonly used to connect it to a circuit. The input terminals of the relay are connected to a switch, a microcontroller, or any other. The circuit or object that has to be controlled is linked to the relay’s output terminals. The relay switches its contacts in response to the control signal, permitting or preventing current flow in the output circuit.

What are the parts of an electronic relay

What are the parts of an electronic relay
What are the parts of an electronic relay

An electronic relay’s essential elements are as follows:

● Coil: This partis responsible for creating the magnetic field.
● Contacts: Through this part, electrical current travels when a relay is switched.
● Armature: The magnetic field created by the coil attracts or repels the armature, a moveable component of the relay. It is coupled to the contacts, which move when the coil is powered up or powered down.
● Spring: When the coil is de-energized, the spring applies the necessary force to move the contacts back to their initial position. It guarantees a steady and dependable switching motion.
● Housing: The relay’s housing, also known as its container, protects its interior parts and offers mechanical support. Usually composed of metal or plastic, it could feature mounting options for simple installation.
● Terminals: These terminals provide safe wire attachment and proper electrical connection.

How do you test an electrical relay

How do you test an electrical relay
How do you test an electrical relay

You can use the general procedures below to test an electrical relay:

● Maintain safety: Make sure all voltage sources are disconnected and turn off the circuit’s power source.
● Visual examination: Examine the relay for any physical blemishes, loose connections, or burned parts.
● Test of continuity: To determine whether the relay’s coil is intact, use a multimeter in the continuity or resistance modes.
● Contact capabilities: According to the manufacturer’s instructions, power the relay coil. Then, while the relay is in its various operating states (usually open and normally closed), use the multimeter to test the contacts’ continuity. Check to see if the contacts switch on and off properly when the coil is powered on or off.
● Coil voltage test: Lastly, you can gauge the voltage across the coil terminals when the relay is powered on. Make that the voltage measured matches the voltage required.


Relays enable precise control and protection in a variety of applications, making them essential parts of electronics. Relays provide the capability to switch high-power loads and automate complex tasks, whether it be in industrial automation, power distribution, automotive systems, or home automation. Electronic relay can be used efficiently to improve circuit performance and guarantee safe and dependable operations by understanding their types, working principles, and testing procedures.


● Electromechanical Relays
● Solid-State Relays (SSRs)
● Reed Relays
● Time Delay Relays

● Coil
● Contacts
● Armature
● Spring
● Housing
● Terminals

● Maintain safety
● Visual examination
● Test of continuity
● Contact capabilities
● Coil voltage test




My name is Kate and I am an electronic engineer with 5 years of experience in IBE Electronics, especially in PCB-PCB design and assembly, electronic components and other related fields. Major in electrical engineering and I have been working in the electronics industry since I graduated in 2018. My greatest passion is to share all the PCB and PCBA knowledge I know with people I meet through articles or communications, whether you are new to the industry or seasoned experts.

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