ClassX Video Lessons Youtube Channel The Engineering Mindset How Relays Work – Basic working principle electronics engineering electrician amp
Welcome to an exploration of relays, a fundamental component in electronics and electrical engineering. In this article, we will delve into the main parts of relays, their types, and how they function. Relays are essential for controlling circuits with low power signals and ensuring electrical isolation between different circuits. Let’s dive in!
A relay is an electrically operated switch. Traditionally, relays use an electromagnet to mechanically operate the switch, but modern versions, such as solid-state relays, utilize electronics. Relays are crucial when controlling a circuit with a low power signal or when one signal needs to control multiple circuits. They help reduce the current flowing through the primary control switch, allowing a low amperage switch, timer, or sensor to manage a higher capacity load.
Relays consist of two main circuits: the primary side and the secondary side. The primary circuit provides the control signal, which can be activated by a manual switch, thermostat, or sensor. It typically connects to a low voltage DC supply. The secondary circuit contains the load, which could be any device consuming electricity, such as a fan, pump, or light bulb.
On the primary side, an electromagnetic coil generates a magnetic field when current passes through it. This magnetic field can be controlled by adjusting the current. The armature, a small pivoting component, is attracted to the electromagnet when energized, closing the circuit on the secondary side. When de-energized, a spring returns the armature to its original position.
There are two basic types of relays: normally open and normally closed.
In a normally open relay, the secondary circuit is off until the primary circuit is complete. For example, a fan can be controlled using a bi-metallic strip as a switch. The strip bends when heated, completing the circuit and turning the fan on.
In a normally closed relay, the secondary circuit is on by default. This setup can control a pump system to maintain water levels in a tank. When the water level is low, the pump is on. Once the desired level is reached, the primary circuit is completed, cutting power to the pump.
Relays can have single or double poles, referring to the number of contacts switched when energized. A double pole relay can control multiple devices, such as a fan and a warning light, from a single primary circuit.
Double throw relays alternate between two secondary circuits. For instance, when the primary circuit is open, a lamp is powered while the fan remains off. Energizing the primary side switches power to the fan, turning the lamp off.
A double pole double throw relay (DPDT) manages two states on separate circuits. When the primary circuit is incomplete, specific terminals are connected, energizing certain devices. Closing the primary circuit changes the connections, powering different devices.
Solid-state relays operate similarly but without moving parts. They use semiconductors for input and output isolation and switching functions. An LED on the primary side provides optical coupling, controlling the relay by turning the LED on and off.
When working with electromagnets, back EMF (electromotive force) is a crucial consideration. When the coil is powered, the electromagnetic field stores energy. Cutting power causes the field to collapse, potentially releasing voltage spikes that can damage circuits. A diode can suppress back EMF, allowing current to flow in one direction and safely dissipating energy.
Relays are versatile components used in various applications. Understanding their operation and types can enhance your knowledge in electrical engineering. For further learning, explore additional resources and continue your journey in electronics.
Engage in a hands-on workshop where you will build a simple relay circuit. This activity will help you understand the physical components of a relay, such as the coil, armature, and contacts. By constructing and testing your relay, you’ll gain practical insights into how relays function and their role in controlling circuits.
Use simulation software to model different types of relays, including normally open, normally closed, and solid-state relays. Experiment with various configurations and observe how changes in the primary circuit affect the secondary circuit. This virtual lab will reinforce your understanding of relay operations without the need for physical components.
Analyze real-world case studies where relays are used in industrial applications. Discuss the advantages and challenges of using relays in these scenarios. This activity will help you appreciate the practical applications of relays and the considerations engineers must take into account when designing relay-based systems.
Participate in a troubleshooting challenge where you diagnose and fix issues in relay circuits. This activity will develop your problem-solving skills and deepen your understanding of common relay malfunctions, such as contact wear or coil failure, and how to address them effectively.
Work in groups to research and present on advanced relay types, such as double pole double throw (DPDT) relays and solid-state relays. Each group will focus on a specific type, exploring its unique features, advantages, and applications. This collaborative activity will enhance your research and presentation skills while expanding your knowledge of relay technology.
Here’s a sanitized version of the provided YouTube transcript:
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[Applause] Hello everyone, Paul here from engineeringmindset.com. In this video, we’re going to explore relays, covering their main parts, different types, and how they work. For all your relay needs, check out Telecontrols, who have kindly sponsored this video. Telecontrols has been a leading manufacturer in the automation industry since 1963, offering reliable switching relays and ensuring the maximum lifespan for your equipment. You can view their switching relay portfolio, along with suitable relay bases and accessories. For more information, you can contact them via email at [email protected] or through LinkedIn to receive your free relay configuration cheat sheet. The link is in the video description below.
A relay is an electrically operated switch. Traditionally, relays use an electromagnet to mechanically operate the switch; however, newer versions utilize electronics, such as solid-state relays. Relays are used when it is necessary to control a circuit using a low power signal or when several circuits must be controlled by one signal. They ensure complete electrical isolation between the controlling and controlled circuits. Relays are often used in circuits to reduce the current flowing through the primary control switch, allowing a relatively low amperage switch, timer, or sensor to control a much higher capacity load.
There are two main circuits in a relay: the primary side and the secondary side. The primary circuit provides the control signal to operate the relay, which could be controlled by a manual switch, a thermostat, or another type of sensor. The primary circuit is generally connected to a low voltage DC supply. The secondary circuit contains the load that needs to be switched and controlled. A load refers to any device that consumes electricity, such as a fan, pump, compressor, or light bulb.
On the primary side, we find an electromagnetic coil, which generates a magnetic field when current passes through it. When electricity flows through a wire, it creates an electromagnetic field, which can be demonstrated by placing compasses around the wire. When current passes through, the compasses change direction to align with the electromagnetic field. Wrapping the wire into a coil combines the magnetic fields of each wire to form a larger, stronger magnetic field. We can control this magnetic field by adjusting the current.
At the end of the electromagnet, we find the armature, a small component that pivots when the electromagnet is energized, attracting the armature. When the electromagnet is de-energized, the armature returns to its original position, typically aided by a small spring. Connected to the armature is a movable contactor. When the armature is attracted to the electromagnet, it closes and completes the circuit on the secondary side.
There are two basic types of relays: normally open and normally closed. In a normally open relay, no electricity flows in the secondary circuit, meaning the load is off. However, when current passes through the primary circuit, a magnetic field is induced in the electromagnet, attracting the armature and closing the circuit to provide electricity to the load. In a normally closed relay, the secondary circuit is normally complete, meaning the load is on. When current passes through the primary circuit, the electromagnetic field causes the armature to push away, disconnecting the contactor and breaking the circuit, cutting the power to the load.
The operation of solid-state relays (SSRs) is similar in principle but has no moving parts. SSRs use electrical and optical properties of solid-state semiconductors for input and output isolation as well as switching functions. Instead of an electromagnet, an LED on the primary side provides optical coupling by shining a beam of light across a gap into a photosensitive transistor. The operation of this type of relay is controlled by turning the LED on and off.
There are many types of relays, and we will now consider a few main ones along with simple examples of their applications. Let me know in the comments how and where you’ve seen relays used, or share your ideas for their applications or any projects you’re working on.
As mentioned earlier, we have the simple normally open relay, which means the load on the secondary side is off until the primary circuit is complete. This can be used, for example, to control a fan using a bi-metallic strip as a switch. The bi-metallic strip bends as it heats up, completing the circuit and turning the fan on for cooling.
We also have normally closed relays, where the load on the secondary side is normally on. For instance, this can control a pump system to maintain a certain water level in a storage tank. When the water level is low, the pump is on, but once it reaches the desired level, it completes the primary circuit and cuts the power to the pump.
In a standard normally open relay, once the primary circuit is de-energized, the electromagnetic field disappears, and the spring pulls the contactor back to its original position. However, sometimes we want the secondary circuit to remain live after the primary circuit is reopened. For that, we can use a latching relay. For example, when we press the call button on an elevator, we want the light on the button to remain on, indicating that the elevator is coming. Latching relays can achieve this.
Relays can have single or double poles, with the term “pole” referring to the number of contacts switched when the relay is energized. This allows multiple secondary circuits to be energized from a primary circuit. For example, a double pole relay can control a cooling fan and a warning light. Both are normally off, but when the bi-metallic strip gets too hot, it completes the circuit, creating an electromagnetic field that closes both contactors on the secondary side, providing power to both the fan and the warning light.
When working with relays, you may hear the term “throws,” which refers to the number of contacts or connection points. A double throw relay combines normally open and normally closed circuits. It alternates between two secondary circuits. For instance, when the primary circuit is open, the spring pulls the contactor to one terminal, powering a lamp while the fan remains off. When the primary side is energized, the electromagnet pulls the contactor to another terminal, powering the fan and turning the lamp off.
A double pole double throw relay (DPDT) controls two states on two separate circuits. When the primary circuit is not complete, certain terminals are connected, energizing specific lights. When the primary circuit is closed, the connections change, powering different devices.
One important consideration when working with electromagnets is back EMF (electromotive force). When we power the coil, the electromagnetic field builds up and stores energy. When we cut the power, the field collapses quickly, releasing stored energy and potentially causing large voltage spikes that can damage circuits. To mitigate this, we can use a diode to suppress back EMF, allowing current to flow in one direction and providing a safe path for the coil to dissipate energy.
That’s it for this video! To continue your learning in electrical engineering, check out one of the videos on screen now, and I’ll catch you in the next lesson. Don’t forget to follow us on Facebook, LinkedIn, Instagram, and Twitter, as well as visit engineeringmindset.com.
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This version removes any informal language, maintains a professional tone, and ensures clarity while preserving the essential content.
Relays – Electromechanical devices used to control a circuit by a low-power signal, or where several circuits must be controlled by one signal. – In the laboratory, we used relays to switch the high-voltage circuits safely.
Circuits – Closed paths through which electric current flows or may flow. – The professor demonstrated how to design circuits that minimize power loss.
Electromagnet – A type of magnet in which the magnetic field is produced by an electric current. – The experiment involved using an electromagnet to lift metallic objects, illustrating the principles of electromagnetism.
Current – The flow of electric charge in a conductor, typically measured in amperes. – Understanding how current flows through different materials is fundamental in electrical engineering.
Voltage – The electric potential difference between two points, which drives current through a circuit. – The lab session focused on measuring voltage across various components to understand their behavior in a circuit.
Components – Individual parts or elements that make up an electrical circuit, such as resistors, capacitors, and transistors. – Selecting the right components is crucial for building efficient electronic devices.
Signals – Electrical or electromagnetic waves used to convey information from one place to another. – The course covered how to process signals for communication systems effectively.
Isolation – The separation of electrical circuits to prevent unwanted current flow, often for safety or noise reduction. – Engineers use isolation techniques to protect sensitive equipment from electrical interference.
Engineering – The application of scientific and mathematical principles to design and build structures, machines, and systems. – Engineering students must understand the principles of physics to solve complex problems.
Electronics – The branch of physics and engineering concerned with the behavior and movement of electrons in semiconductors, conductors, and vacuum. – The electronics lab provided hands-on experience with designing and testing circuits.
