What is relay logic circuit? Relay logic is a method of OPERATING industrial electrical circuits with the help of relay and contacts. In RLC, we use relay contactor mechanical timer counter etc. These are basic element for RLC. To understand and create RLC, we must have to know about the basic element.

First we understand what is NO and NC point. RLC depend on both point NO and NC.

NO point :-NO point is normally open. It means that point is normally open in ideal state. To understand about NO point see figure:-

In this figure when this point is in ideal state no output comes from it , but when we activate this point it close and output comes.

NC POINT:- Full form of NC is Normally Close. It means NC point is close in ideal state. See figure to understand this point

In this figure when this point is in ideal state output comes from it, but when we activate this point, it opens and no output comes.

RELAY:- Relay is most important function in RLC. Without relay we can not assumes to create RLC. Relay is a electrical operated switch. first relay is invented in 1835 for telegraphy by JOSEPH HENRY. After few year relay become use for different purpose and application.

Relay is an Electromechanical device which operates by current. Relay consists one coil, armature, spring and contact as shown in images.

In above block diagram, there is coil which consist two terminal A1 and A2. When we give supply on these terminal (A1, A2), coil generate magnetic field which attract or repel armature which is in coil. That Armature end terminal connects with contact. When coil operate armature, operating contact became change and when supply cut off, contact goes to ideal state with the help of spring.

Mainly use of relay is switch electric supply. Suppose your controlling voltage is 12V. But we want to control 24V equipment. Here we use 12V operating Relay and 24v Bulb. See image to understand this example.

CONTACTOR:- working principle of contactor is same as relay, but it mainly uses for heavy duty work. Contactor Switching time is higher than relay.

Switch:- This element uses for interface between machine and human or operator. There are many type of button as Momentary switch, Selector switch, toggle switch and latch switch. Switch is operated by human. Using switch, Human give signal or command and control to machine or circuit. Switch has two states ON and OFF.

Momentary switch:- In this type of switch, when we press this switch, it gives signal and when release signal off.

Selector switch:-  This switch use for multiple selection from one switch. It is use for select one circuit in many circuit.

Toggle switch:– In this type of switch , normally it is ON or OFF. When we press or operate this switch , it will latch this state again we operated this switch than it goes to ideal state.

Timer:-  As per name it is timer,  a particular time we set in this device, after completing time, it’s relay on. Timer has two element, timer and relay. Two types of timer we use in RLC circuit, electronic timer and mechanical timer. With help of following timing diagram we can easily understand working of timer.

When we give supply to timer, timer run and after completing set time (T) timer’s relay on.

We can use timer as ON delay and OFF delay. In ON-delay timer, relay ON after completing time. But in OFF delay timer, relay OFF after completing time

In next chapter (relay logic circuit-chapter-2) we will discuss about how we can create relay logic circuit using these above elements. If you have any problem or query with this topic please comment below or contact us info@yuvayana.org . With your help we can improve our system and topic.

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