Relays are electronic components commonly used in the industrial and electronics sectors. They are essential devices in many types of equipment and systems, ranging from household appliances to industrial machinery. In industrial projects, the use of relays is essential to precisely and safely control many processes and tasks. These are devices that can even be programmed to provide total control over a machine, device, or piece of equipment.
Below, we will see what a relay is and how it works, what its main uses are, and what types we can find on the market.
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What is a relay?
A relay is an electrical component used to control the flow of current in an electrical circuit, as it works like a switch that is activated or deactivated by an electrical signal coming from another circuit. The relay is capable of controlling high-current and high-voltage loads, which makes it especially useful in applications where it is necessary to control high-power electrical devices such as motors, pumps, and lights, among others.
Therefore, a relay is basically an electrically operated switch, meaning it is activated through the use of electrical current that flows through its circuit. When a relay is implemented in a circuit, that circuit is being controlled using another different circuit (the relay’s own circuit).
What are relays used for?
Relays have many applications in industrial environments and in the world of electronics and electricity. Let’s look at some of the most common uses of these devices:
- Control of electrical devices. They are commonly used to control electrical devices such as motors, pumps, lights, or solenoid valves.
- Process automation. In industry, relays are often used to automate processes, such as controlling machinery in a factory, opening and closing doors, or activating lighting systems.
- Safety and protection. These electronic components are commonly used to detect errors and faults in electrical systems, and thus activate alarms sent to operators or directly shut down the system (to prevent accidents or major damage).
- Temperature control. Thanks to thermal relays, it is possible to control temperature in systems such as boilers, ovens, motors, and other processes.
How does a relay work?
A relay usually contains two contact points (one open and one closed). When current flows through its coil, a magnetic field is generated that creates an electromagnet, causing the contacts to change position. In this way, the relay works like a switch that allows control of systems, devices, sensors, etc. The main components of most relays are:
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Coil. This is the component of the relay that receives electrical current to produce a magnetic field that activates the relay switch.
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Contacts. These are the switches activated by the coil. They can be normally open (NO), normally closed (NC), or changeover (C).
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Spring. A mechanical component of the relay that returns the contacts to their original position when the coil is deactivated.
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Armature. The moving part of the relay that is connected to the contacts and moves when the coil is activated.
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Core. The core is usually made of iron or steel, located inside the coil, and concentrates the magnetic field produced by the electric current.
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Housing. The external structure of the relay that protects the internal components and provides a place to mount the relay on a board or device.
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Terminals. The electrical connection points of the relay where the cables or electrical circuits are connected.
Types of relays
We can distinguish between the following types of relays:
Conventional electromechanical relays
These relays use an electromagnet to open or close one or more electrical contacts. They are made up of a coil, a movable core, and several contacts. When current is applied to the coil, a magnetic field is generated that attracts the movable core, causing the contacts to open or close.
They are the most common and are used in applications such as motor control, overload protection, and the switching of electrical circuits.
Moving core relays
The moving core relay is based on a core that moves inside a coil. When the coil is activated, the core moves and activates the electrical contacts.
Moving core relays are used in applications that require a high switching speed and are very common in the automotive sector.
Polarized relays
Polarized relays have an electromagnet at one end that makes it rotate, and at the opposite end a contact. When electric current flows, the electromagnet is activated and closes the contact (depending on its polarity, it will guide it in one direction or another).
They are useful in applications where it is necessary to keep a contact closed for long periods of time, such as in control circuits.
Reed-type relay
This type of relay uses a Reed switch, which consists of a set of metal blades inside a glass tube filled with inert gas. When a magnetic field is applied, the blades come together to complete the electrical circuit.
They are useful in applications where a low energy consumption relay and high switching speed are required.
Solid-state relay
When we talk about solid-state relays, we mean those that do not have moving parts and use a semiconductor to control electrical current.
They are very useful in high-speed and high-frequency applications, since they can change state in a fraction of a second. They are also very durable and resistant to vibrations and shocks.
We have seen what a relay is and how it works, in addition to highlighting some of its main types. In industry, relays are one of the basic components to control the operation of machinery, devices, and equipment, ensuring that industrial processes are carried out in a safe, precise, and fault-free environment.
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