The brightness can be controlled using the IR remote of TV, DVD, etc. Dimming Control system using MOC3021, BT136 Triac and a zero-crossing detector circuit based on the MCT2E optocoupler. Optocoupler provides complete isolation between the AC side and the DC controller side. So if any fault or short circuit happens on the AC side will have no effect on the controller side.

In this tutorial, we will design a circuit using TRIAC and optocoupler to make a 220V AC Light Dimmer or AC Fan Speed Controller using Arduino UNO. most of the home appliances are supplied with the AC mains power. Sometimes we need to control the brightness of bulb or Speed of Fan/ AC Motor etc or any other dimming control for an instant. Controlling an AC load is not as easy as controlling a DC load. The AC mains with a sinusoidal wave have the frequency of 50Hz to 60 HZ.

The most popular and proper way for Dimming of 230v AC is through phase control with a Triac. To build an AC dimmer, the zero-crossing detector circuit used and zero-crossing points (the points where the wave changes its polarity) are important. A zero-crossing detector is used to generate a sync pulse related to the AC voltage phase angle often used in power control circuits. Zero crossing detector basically detect zero voltage points and inform the controller or controller circuit. It helps to minimize high rate change of current with respect to time (dI/dt) as a result less heating and start-up current in the load which improves the lifetime of load such as motors. A Zero Crossing Detector can be designed in many ways like using transistor, using op-amp or using optocoupler IC

bridge rectifier converts ac into dc

Output of bridge rectifier is fed to opto-coupler

Led inside the optocoupler requires minimum of 1V to turn on

when ac wave goes near to the zero crossing line,ie below 1V led will turn off

as a result output transistor will turn of and pulled up to 5v

The zero-crossing technique is one of the methods enabling to evaluate the delay time of propagating waves.

In this project I’m going to show how to a remote used to control the circuit for the Dimmer, so that the lamp brightness is controlled from IR remote control instead of the potentiometer.

Connect the circuit as per the given schematic diagram. You can use DB107 or other bridge rectifier ic at the place of 4 separate 1N 4007 diodes. Here I use 2 55k resistor to limit the current from AC input to rectifier, an Optocoupler ic connected, here 4N35 is connected but you can use MCT2E or PC817 etc. In optocoupler ic there is an LED and NPN transistor. connect negative supply from bridge rectifier to pin 2, this is the negative pin of the LED of the optocoupler. the positive terminal of LED at pin 1 in this optocoupler. The emitter of the transistor is connected with the ground pin of Arduino and collector pin which is at pin 5 of optocoupler ic is directly connected with digital input pin of Arduino and one 10K resistor is with pin 5 is connected to +5v of Arduino, here this resistor is working as a pull-up resistor.

Schematic diagram

#include <IRremote.h>

int RECV_PIN = 2;

IRrecv irrecv(RECV_PIN);

decode_results results;

void setup()

{

 Serial.begin(9600);

 // In case the interrupt driver crashes on setup, give a clue

 // to the user what's going on.

 Serial.println("Enabling IRin");

 irrecv.enableIRIn(); // Start the receiver

 Serial.println("Enabled IRin");

}

void loop() {

 if (irrecv.decode(&results)) {

   Serial.println(results.value, DEC);

   irrecv.resume(); // Receive the next value

 }

 delay(150);

}