Wireless AC Light Dimming Using Arduino

We have AC loads all around us. And the majority of household appliances are powered by alternating current (AC). There are numerous situations in which we want complete control over an AC load, such as dimming a lamp, controlling the speed of an AC motor/fan, controlling a vacuum cleaner, and many other applications. The proper method for dimming 230v AC is to use phase control with a Triac: the Triac is then fully opened, but only during a portion of the sinus AC wave. However, controlling an AC load is more difficult than controlling a DC load. The electronic circuit for each of these applications is unique. The frequency of the alternating current mains with a sinusoidal wave is 50Hz. The zero-crossing points (the points where the wave changes polarity) are critical when building an AC dimmer. To detect these points, we must first construct a zero-crossing detector. Similarly, we must control the waveform’s phase and cycle. Because every component can not withstand 220V AC, we must isolate the circuit from 220V AC using another component.

Materials List

The following are the components needed to complete the AC Dimmer Project. Eagle Electronics sells all of the necessary components.

Hardware Connections

Arduino Hardware Connections

AC Dimmer Module & Bulb Connections

Downloads

• Mobile Android Application

Program/Source Code

The Arduino Program to Control the AC Dimmer with Bluetooth is provided below, along with comments to help you understand how the AC Dimmer works. Simply copy and paste this code into your Arduino board.

#include <SoftwareSerial.h>

#include <TimerOne.h>           

volatile int i=0;               // Variable to use as a counter

volatile boolean zero_cross=0;  

int AC_pin = 3;                // Output to Opto Triac

int POT_pin = A3;             // Pot for testing the dimming

int led = 13;                    // LED for testing

int dim = 0;                    // Dimming level (0-128)  0 = on, 128 = 0ff

long ch = 0;

int freqStep = 75;    // This is the delay-per-brightness step in microseconds.

void setup()

{                                      // Begin setup

Serial.begin(9600);

Serial.setTimeout(10);

pinMode(AC_pin, OUTPUT);                          // Set the Triac pin as output

pinMode(led, OUTPUT);                             // Set the LED pin as output

attachInterrupt(0, zero_cross_detect, RISING);   // Attach an Interupt to Pin 2 (interupt 0) for Zero Cross Detection

Timer1.initialize(freqStep);                      // Initialize TimerOne library for the freq we need

Timer1.attachInterrupt(dim_check, freqStep);

}

void zero_cross_detect()

{

zero_cross = true;               // set the boolean to true to tell our dimming function that a zero cross has occured

i=0;

digitalWrite(AC_pin, LOW);

}

// Turn on the TRIAC at the appropriate time

void dim_check() {

if(zero_cross == true) {

if(i>=dim) {

digitalWrite(AC_pin, HIGH);  // turn on light

i=0;  // reset time step counter

zero_cross=false;    // reset zero cross detection

}

else {

i++;  // increment time step counter

}

}

}

void loop()

{

// dim = analogRead(POT_pin) / 8;  // read dimmer value from potentiometer

// analogWrite(LED, dim);  // write dimmer value to the LED, for debugging

while(Serial.available())

{

ch = Serial.parseInt();

dim = ch;

dim = 128 – dim;

analogWrite(led ,dim);

}

}

 Project Video