Control AC Light Using Arduino

About: ignite.innovate.ideas

The first tutorial everyone suggest in arduino is Blinking a LED. Today I will show you how to control a AC light/appliance with the same Blink sketchControlling AC light or appliance with arduino is simple as blinking a LED using arduino.

All you need to is take proper care while doing this project because here we are dealing with AC current (230V is more than enough to kill you).So beware

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Step 1: Things You Need



  • AC BulbBulb
  • Socketscrew
  • terminal connector

Step 2: Before We Build

What is a relay?

Relays are switches that open and close circuits electromechanically. They control one electrical circuit by opening and closing contacts in another circuit

A relay have 5 pins namely COIL A, B, NO, NC,COM

There are 5 Pins in a relay. Two pins A and Bare two ends of a coil that are inside the relay. The coil gets energized whenever current passes through it.

NC = Normally Closed, is connected to pin when the relay coil is not energized.

NO = Normally Open, is left disconnected when relay coil is not magnetized and is connected COM when the relay coil is energized.topin when the relay coil is not energized.

COM = Common, At no input state, the COM is connected to NC. When the operating voltage is applied to relay coil gets energized and the COM changes contact to NO

Why BC547 ?

5V Relay needs about 200mA current at 5V. But the digital pins of arduino provides only 20 mA current. So arduino can not drive the relaydirectly.So as amplifier we need to used a transistor to drive the relay

Why Diode ?

The relay coil cannot change it’s current instantly, diode provides a path for the current when the coil is switched off. Otherwise, a voltage spike will occur causing arcing on switch contacts or possibly destroying switching transistors

Step 3: Watch the Video

Step 4: Lets Start Building

The circuit is very simple and small, there is only few thing to place.

Wire as per the below given schematics

This is just a illustration of the circuit

Step 5: Upload Code to Arduino

There is not need to download any code you have the code within the software just upload the Blink Sketch and watch the AC light blinking as a LED blinks

This is just basic tutorial on interfacing Relay with arduino.This project can improved to higher level like Home automation using smartphone,Clap switch and much more
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    3 Discussions


    3 years ago

    Thanks, Nice explanation. I may be able to use this as the start of an arduino project.