What is Relay?

What is Relay?

Relay (relay, English word – relay) Although electrical equipment is special, but their importance in electronics is not less.  Suppose I made a flip flop with which the LED is on and off.  Now if I want to turn a large lamp on and off automatically by this flip flop circuit then I have to take the help of a device/component which can be connected to that small circuit so that this high power lamp can be switched on and off  Can go.

This is possible in a number of ways, but the most common and popular method is the use of a relay.  Using this, I will be able to drive any lamp, fan or device connected to high voltage through a low voltage electronic circuit.  This article is dedicated to the novice hobbyist and interested readers who are working with electronics in spite of various limitations.  If they benefit, then my work is worthwhile.

 

What is relay ?

It is a kind of electromagnetic device.  In general, if we want to understand, this can be thought of as when we light a lamp with a small switch, we have to turn it on or off with our hands on the switch.  That is, it takes an external force to turn the switch on and off.  In the same way it takes an external force to turn a relay on or off, but in this case the force is electromagnetic force.  i.e. it consists of a coil or temporary electromagnet in which it can switch ON/OFF when it supplies the required amount of power.  So it mainly consists of 2 parts:

  1.    switching part
  2.    electromagnetic part

 

How many types is this?

There are three main types of relays in the market

  •    SPST – Single Pole Single Throw
  •    SPDT – Single Pole Double Throw
  •    DPDT – Double Pole Double Throw

We will learn more about the most common SPDT relays in this lesson.

 

How to watch relay

If we look at the image below we will see what a real relay looks like-

If you look here, you will see that it has 5 legs/feet/sides and some things are written in small letters on it.  Now we will try to understand the meaning of these articles.

 

Which of the following means:

If we look closely, we can see that the text indicates different dimensions of the relay.

As I said earlier, it is made up of 2 different parts.  These texts indicate different values ​​of voltage, current, resistance, etc. of these two different parts.

 

How many volts do I have in this relay?

According to the above figure, there are two types of voltage on it-

10 Ampere, 250 Volt AC / 15 Ampere 120 Volt AC – Refers to the maximum volt-amp tolerance of its internal switch.  On the other hand, the text 12 Volt DC (with some numbers) just below it indicates that the electromagnetic coil used is 12 Volts.  That is, if 12 volts or less (10%-25%) is applied to the electromagnetic part of this relay, the relay will be energized and able to perform its switching function.  These are usually referred to by the voltage of the internal magnetic coil and its switching type, such as the 12 volt SPDT relay.

 

Pins Used in Relays:

From a traditional point of view, like other electronic parts, the legs of a reel were referred to as legs, but for some reason it is referred to as a pin, so we will call it pins later.  If we look at the pin out/pin configuration of the SPDT reel, it looks like this-

As I said earlier, it is made up of 2 different parts.  These texts indicate different values ​​of voltage, current, resistance, etc. of these two different parts.

 

How many volts do I have in this relay?

According to the above figure, there are two types of voltage on it-

10 Ampere, 250 Volt AC / 15 Ampere 120 Volt AC – Refers to the maximum volt-amp tolerance of its internal switch.  On the other hand, the text 12 Volt DC (with some numbers) just below it indicates that the electromagnetic coil used is 12 Volts.  That is, if 12 volts or less (10%-25%) is applied to the electromagnetic part of this relay, the relay will be energized and able to perform its switching function.  These are usually referred to by the voltage of the internal magnetic coil and its switching type, such as the 12 volt SPDT relay.

 

Pins Used in Relays:

From a traditional point of view, like other electronic parts, the legs of a reel were referred to as legs, but for some reason it is referred to as a pin, so we will call it pins later.  If we look at the pin out/pin configuration of the SPDT reel, it looks like this-

It has 3 pins on one side and 2 pins on the other.  Of these, 2 ends are used for the internal coil and the other 3 ends are used for switching.  names of pins or edges, respectively

  1.    NC (Normally Closed)
  2.    No (Normally Open)
  3.    CO (Normal) / Pole
  •    coil + / –
  •    coil – / +

 

NC (Normally Closed):

This pin remains on normally.  i.e. if the reel coil does not have proper power supply, it is connected to the common pin (short).

NO (Normally Open):

This pin remains closed under normal conditions.  That is, if the reel coil does not have a proper power supply, it deviates from the normal pin.  Usually a device/lamp is connected to this pin (NO) and (Common-CO) pin to switch in the circuit.

CO (Normal) / Pole:

This is because it is also called common or CO or pole for the above 2 pins.

Coil:

While switching, a voltage like current is applied by these two pins to the relay.  Usually the LEDs of a circuit can be installed at the place of installation or at the place of installation of the dipper (with suitable capacitor and register).  There is usually no positive/negative edge of the coil in this relay.  This means that the coil can be connected either way to either end of the battery.

 

Understand how my relay type is

By counting the total number of legs/pins, it is easy to understand what type of T is in my relay.  For convenience this chart may be recalled-

  •    SPST – 4 Pin
  •    SPDT – 5 pin
  •    DPST – 6 Pin
  •    DPDT – 8 pin

 

Incidentally, SPST and DPST are rarely available as a double throw is possible with little tactical use on either side of any relay.

 

How many volts are in my relay?

The relay is known by the voltage of its coil, i.e. the voltage at which the coil of the reel is fully energized is considered as the voltage of that reel.  The main reason for this is that the switching end of the reel operates at any voltage, so only the maximum voltage and current conduction level at that end are indicated.  Basically a relay is nothing but a special switch, for this we will open a relay completely and inspect its inside and bring it back to its previous position.

 

What does opening a relay look like?

Now we will look inside the reel and try to understand how it works.  Let us see how it looks when the relay is opened-

For this work we have N.C.  I have used NC Cutter and Mini Precision Screwdriver.  They can cause serious damage if proper precautions are not taken.  Therefore, fresh students will be requested not to attempt it alone (except for adults).

In the figure above we can see an internal image of a SPDT reel.  If you want to understand better then you can see the image given below.

I see in this picture a very close-up image of the same relay.  where is the inside of the tip (contact point) of its various pins

The pole/common edge shown in the picture is able to move and I can see the electromagnetic coil wrapped with a bright thin insulated wire around it.  Basically the common end, attracted by the electromagnet or electromagnet, connects to the NO end and the NC end to complete the relay.

At the end of our observation, we carefully insert the relay into the shell and attach it with super glue.



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