GUIDE FOR SPDT RELAY INTERFACE   WITH ARDUINO UNO

I published the first article. In that I taught you ,how to make a simple led blink project. How did we give the microcontroller a simple command and turn the led ON for one second and then turn the led OFF for one second. Iyou have all ready published LED BLINK ON ARDUINO BOARD WITH SIMPLE ARDUINO PROGRAMMING . You can visit and gain your knowledge. The led we used to create the led blink project. This led take very low voltage for turn ON, like led take voltage 1.5 to 2.5v . We know that the Arduino Uno board have 3.3v and 5v external voltage available. This means from the Arduino Board can be used 3.3v and 5v external voltage. But when we have to control the high voltage loads . Like AC bulb, fridge, cooler, Tv, etc has to be controlled. There will not be enough 5v voltage obtained from Arduino for  high voltage devices. So we used over there any high voltage loads can be easily controlled by relay. Here we will control such AC Bulb by relay. We will turn ON for one second and then imminently turn OFF for one second by the simple led blink code. In this article, all the connection of relay module will see, how is interface with Arduino and how is the connection  of AC bulb in the relay.

WHAT IS SPDT REALY ?

The relay is a electrotechnical switch . Which high voltage loads or high current loads is used for control. The relay is specially designed to switch ON and switch OFF with high voltage loads by signal. Relay can be easily controlled to Ac, fridge, cooler or any high voltage loads by any circuits or microcontroller. There are many variants of relays available in the market. Which operates different- different dc voltages according to loads. Like relay operates 5v, 12v, 24v Dc power supply and 1, 2, 4, 8, 16, 32, channel relays are available in the market.

HOW SPDT RELAY WORKS ?

The SPDT (Single Pole Double Through) relay is an electrically operated switch. Which control high power loads by using low dc power supply. Lets understand the internal function of relay. There is a Coil inside the SPDT relay. There is a Common (com) terminal, a Normally Close (NC) and Normally Open (NO) terminal in the Relay.

When relay of coil is rest position. It means there is no current flow through the coil. So the movable contact attached the common terminal is connected with NC terminal. And when the current flow through the coil. So in coil starts generating electromagnetic field, which coil makes behave like a magnet. So coil toward attract the movable contact of common terminal. Which connected the movable contact with NO terminal. And  when as soon as stopped current flow through the coil. So finished the electromagnetic field made in the coil. Due to which the com terminal of movable contact comes in it's reposition. That means movable contact is again reconnected to NC terminal. This is how relay works? and switches high voltage operated loads ?

PINOUT

Here we are using one channel SPDT relay operating from 5v dc. The relay module is divided into two section. 1st Low power section and 2nd High power section.

In Low power section has VCC , GND, 1N(Signal pin).

VCC - 5V DC power supply is delivered via VCC pin to operate the relay.

        

 GND   - Ground is provided to GND pin or relay.

   1N     - Signal is provided by Microcontroller or circuits in 1N Pin  relay for switch the load.   

In High power section has Common(Com), NC, and NO Terminal.

COM   - The Com terminal is used to connect the AC power supply  or DC power supply. Depend on you, which power supply you want to connect and for switch the load.

   NC    - The NC (Normally Close) terminal is used to keep permanent ON the load and if the load is to be switched OFF certain condition. 

   NC    - The NO (Normally Open) terminal is used to keep permanent OFF the load and if the load is to be switched ON certain condition. 

COMPONENT REQUIRED

• Arduino Uno
• One Channel SPDT relay module
• AC Lamp
• Battery
• Jumper wire
• Bread board       

INTERFACE ONE CHANNEL RELAY MODULE TO ARDUINO UNO

Warning:- This Board interacts with High AC voltage. Incorrect  or improper use could result in serious injury  death.So it is intended for people experianced around and knowledgable  about high AC voltage.

  RELAY       -    ARDUINO UNO

   VCC           -   5V Pin

   GND          -   GND Pin

   1N              -   Digital Pin (D5)

Let's set up Ac Lamp in relay first of all you have to pay attention that all the power supply switches must be switch off before connection such Ac lamp to the relay. To give Ac supply to the lamp. Which goes two such Ac wires. None of them connect such one ac wire direct to the lamp. Keep in mind that all power supply switches should be closed while making connection. Then after other cut of wire from the middle. The cut one end of that ac wire connect directly to AC power supply. And cut other end of ac wire connects directly to the lamp. One end of the cut wire that connects to the direct ac supply, connect that cut wire to the COM terminal of relay. And other cut wire that connects to the lamp, that wire directly connect to the NO. Because here we want to keep the lamp permanent OFF and if the lamp is to be switched ON due to certain condition. If the lamp is to be switch ON for a long time, So you can connect to the NC terminal. So this way you guys have to connect any load to the relay. 

CODE

int Led =5;

void setup()

{

pinMode(Led, OUTPUT);

}

void loop()

{

digitalWrite(Led, LOW);

delay(1000);

digitalWrite(Led, HIGH);

delay(1000);

}