Question: Why Relay Is Used In PLC?

How do you control a relay?

When you activate the relay by applying an appropriate voltage to the control circuit, the electromagnetic coil in the relay activates and pulls the switch open, stopping any current flowing through the switched circuit..

What is difference between PLC and relay?

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.

Why do we use a relay?

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. … In an automobile, a starter relay allows the high current of the cranking motor to be controlled with small wiring and contacts in the ignition key.

What is transistor output in PLC?

A transistor output is a solid-state device that handles small to medium amount of current. Most transistor outputs in our PLC range can only handle DC current up to the power supply voltage of the PLC. (i.e. either 12VDC or 24VDC). A relay is an electrically operated switch.

Where is relay used?

Relays are used to provide time delay functions. They are used to time the delay open and delay close of contacts. 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.

How a relay is wired?

What is a Relay and How Does it Work? A relay is an electrically operated switch. They commonly use an electromagnet (coil) to operate their internal mechanical switching mechanism (contacts). When a relay contact is open, this will switch power ON for a circuit when the coil is activated.

Why is a relay better than a switch?

Relays are a better choice for switching large currents (> 5A). Relays can switch many contacts at once. Disadvantages of relays: • Relays are bulkier than transistors for switching small currents. Relays cannot switch rapidly (except reed relays), transistors can switch many times per second.

What are the two types of relay?

Types of Relays – A Thomas Buying GuideRelays are electrically operated switches. … Electromechanical relays have an electromagnetic coil and a mechanical movable contact. … Solid-state relays are solid-state electronic components that do not have any moving components, which increases their long-term reliability.More items…

What is a relay symbol?

A single pole switch is often denoted by the letters SP, and a double pole by DP. Relays can have one, two or more poles. Throw: The number of throws on an electrical switch is the number of positions that are available. For an electromechanical relay, there are normally only one or two throws.

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. … This type of output can control lamps and low power DC circuitry such as small DC relays.

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 digital input and output in PLC?

Digital I/O stands for Digital Input and Output. Digital Inputs allow a microcontroller to detect logic states, and Digital Outputs allow a microcontroller to output logic states. Each digital I/O on a LabJack can be individually configured to one of 3 states: input, output-high, or output-low.