Quick Answer: Why Relay Is Used In PLC?

What are the three types of PLC?

PLC are divided into three types based on output namely Relay output, Transistor output, and Triac Output PLC.

The relay output type is best suited for both AC and DC output devices.

Transistor output type PLC uses switching operations and used inside microprocessors..

What is a relay symbol?

The circuit symbols for electromechanical relays can vary somewhat – like most circuit symbols. The most widely used format shows the relay coil as a box, and the contacts are placed close by as shown below. Circuit symbol of a relay. Note that on this symbol, both normally open and normally closed contacts are shown.

Is a relay analog or digital?

The switching function of a mechanical relay is necessarily digital; it either connects or doesn’t. The nature of the signal, thus connected or not, is analog from the perspective that any voltage may be conducted, that doesn’t exceed the flash-over voltage of the contacts.

Where is relay used?

Relays are used to control high voltage circuits with the help of low voltage signals. Similarly they are used to control high current circuits with the help of low current signals. They are also used as protective relays. By this function all the faults during transmission and reception can be detected and isolated.

Why relay is used?

Relays are used wherever it is necessary to control a high power or high voltage circuit with a low power circuit, especially when galvanic isolation is desirable.

What is Relay and its types?

A relay is a switching device as it works to isolate or change the state of an electric circuit from one state to another. Different Types of Relays. Classification or the types of relays depend on the function for which they are used.

What is Relay output?

A relays Output Circuit is the portion of the relay that switches on the load and performs the same function as the mechanical contacts of electromechanical relays. Solid-state relays, however, normally have only one output contact.

What is Relay output in PLC?

Relay outputs are mechanical contacts and solid state outputs may take the form of transistor or TTL logic (DC) and triac (AC). Relay outputs are usually used to control up to 2 amps or when a very low resistance is required. Transistor outputs are open collector common emitter or emitter follower.

What is I O module in PLC?

PLC I/O modules are one of the three core components that operate a programmable logic controller. I/O refers to input/output. PLC I/O modules act as messengers between a processor and an I/O device.

What are the 4 main components of a PLC?

The basic components include a power supply, central processing unit (CPU or processor), co-processor modules, input and output modules (I/O), and a peripheral device.

What is Relay and its application?

Application Of Relay Relays are used for isolating a low voltage circuit from high voltage circuit. They are used for controlling multiple circuits. They are also used as automatic change over.

What is Relay and its function?

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.

What is digital input and output in PLC?

A “discrete” data point is one with only two states on and off. Inside each discrete input module is (typically) a set of light-emitting diodes (LEDs) which will be energized when the corresponding sensing device turns on. …

What is the function of relay in PLC?

After all, the main purpose of a plc is to replace “real-world” relays. We can think of a relay as an electromagnetic switch. Apply a voltage to the coil and a magnetic field is generated. This magnetic field sucks the contacts of the relay in causing them to make a connection.

Why relay is used in motor control?

Control relays are electronic parts that are used in motors, power plants, power supply systems, transistors, and more. Control relays permit a low current circuit to control a high current circuit. … First, when electrical current flows through a coil, it draws in a magnetic substance that closes the device’s switch.

What is the difference between relay and PLC?

The difference between a PLC and relay logic is that a PLC is a programmable device whereas relay logic is a network of hardwired electrical devices. Both a PLC and relay logic can perform logical computation, but a PLC does it using a microprocessor and relay logic does it using electric circuits.

What is the basic of PLC?

Basic PLC operation. The basic elements of a PLC include input modules or points, a Central Processing Unit (CPU), output modules or points, and a programming device. … The CPU evaluates the status of inputs, outputs, and other variables as it executes a stored program.

Why do we use relays?

A relay is an electrical device that closes one circuit by being energized by another circuit. These can be used for many reasons. … When we use a relay to power a high voltage or high current device, while a lower voltage is used to power the controls that energize the relay.