Why Use A Relay Instead Of A Switch?

What is NO and NC in PLC?

The normally open contact (NO) is true (closed) when the input or output status bit controlling the contact is 1.

The normally closed contact (NC) is true (closed) when the input or output status bit controlling the contact is 0..

What’s the difference between a relay and a contactor?

Contactors are typically built for and used in 3-phase applications where a relay is more commonly used in single phase applications. A contactor joins 2 poles together, without a common circuit between them, while a relay has a common contact that connects to a neutral position.

Which transistor is best for switching?

Best Transistors: BJTs#1 NPN – 2N3904. You can find most often NPN Transistors in low-side switch circuits. … #2 PNP – 2N3906. For high-side switch circuits, you need a PNP style BJT. … #3 Power – TIP120. … #4 N-Channel (Logic Level) – FQP30N06L.

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.

What is the difference between a switch and a relay?

The main difference between Relay and Switch is that the Relay is a electrically operated switch and Switch is a electrical component that can break an electrical circuit. … Many relays use an electromagnet to mechanically operate a switch, but other operating principles are also used, such as solid-state relays.

Why do we use a contactor instead of a relay?

Relays are switching devices used in any control circuit for checking a condition or multiplying the number of contacts available. Contactors are switching devices used to control power flow to any load. Mainly used in control and automation circuits, protection circuits and for switching small electronic circuits.

What is NO and NC In Contactor?

Relays and contactors have two types of contacts, each suited for different applications: Normally open (NO) contacts allow current when the relay or contactor is energized. … Normally closed (NC) contacts allow current through when the relay or contactor is not energized.

Can a transistor be used as a relay?

A transistor is an electronic device that can work as a switch. It allows control of a large current by a smaller current as does a relay. Unlike a relay, however, a transistor is not mechanical, and can operate much faster than a relay.

Why use a relay in a car?

Relays in general are used to enable a low amperage circuit to switch on or off a higher amperage circuit, like turning on your headlights. … Relays are also used to switch multiple things at the same time using one output.

What is difference between NO and NC?

NO is normally open i.e. the contacts are normally open and close when the switch is actuated. NC is normally closed i.e. the contacts are normally closed and open when the switch is actuated.

What is the advantage of using a relay?

The advantage of relays is that it takes a relatively small amount of power to operate the relay coil, but the relay itself can be used to control motors, heaters, lamps or AC circuits which themselves can draw a lot more electrical power.