How to make a Relay Module ?

 How to make a Relay Module?

Introduction :-

When we talk about the electronics indirectly we talks about the controlling of physical world. Electronic devices are capable enough to control the physical world. Generally  we deals with the low voltages in electronic circuits but some time we need to control a huge amount of electricity to run or stop some electrical devices for example when we need to control the main power line from distribution board. Than in general electronic, directly  we have nothing to control this amount of power. So if we want to control this huge amount of power than we have operate a relay as switch of  that further control the main power line.

A Relay Module:- 

A relay module is a electronic device the operates on 10-12 Volts DC but have a capabilities to handle a huge amount of power to switch some kind of electrical devices such as electrical fan , bulb, motor or iron etc. This module can be made some generic electronic components. These components can easily arranged from local market or your own electronic inventory.

The circuit diagram of a relay module is shown in the figure below.

As we can see in the circuit diagram, the incoming signal is fed to the optocoupler IC 4N25 through 1 kilo ohm resistor and LED D1 that switches the internal transistor through photo technique. When this internal transitor get switched on than it further switched on the externel transistor that is BC547 . This BC547 now power on the relay coil with 12 VDC and relay get energied due to this the contacts of relay get switched from NC (Normally Closed) to NO (Normally Opened) and the power given to common pole start going through NO terminal.

Construction:- 

This module required very few generic components. The list components are.

Small Piece of Zero PCB

One 12VDC  Coil Relay (PCB Mountable)

One BC547 Transistor 

One 4N25 Optocoupler IC

Two 1 Kilo Ohm Resistor 1/4 Watts

One IN4007 Diode

One 3 mm LED

7 Male Header Pins  

Soldring Iron and Some Basic tools

Make a  suitable sized zero PCB, it will be better to have holes of approx 3mm at every corner of this PCB piece. These holes are used to fix the relay module . Now assemble and solder  the components as shown in the circuit diagram before .

After finishing the soldring process cut the extra long terminals of components with the help of wire cutter. Now lets check the relay module . To check the relay module folllow the steps given below-

1. Double check the correct ness of soldered circuit.

2. Check for any type of shorting of solder in between tracks.

3. Join the 12VDC to terminal.

4. Give approx 5 VDC to In terminal at input (Jack 1).

5. Check the connectvity between comman to NO terminals at output (Jack 2).

6. If connectivity found than your circuit is okey and ready to use.

This Relay Module can be use to operate a load upto a limit as mentioned on the relay body. When a incoming 5 VDC signal comes the LED glows. It indicates that the optocoupler is working fine at input side. 

If we use new and reliable components than this circuit can withstand for years long. 

So this was for now . We will meet again for another intersting blog. 

Kindly suggest in the comments section.