Circuit used to control the voltage across the TRIAC pin as shown

Published December 29, 2022 © GPL3+

Arduino Based AC Voltage Control using Zero Voltage Crossing

Controlling AC voltage means we are trying to control speed of single phase ac motor or trying to control the brightness of incandescent bul

IntermediateFull instructions provided8 hours1,647

Arduino Based AC Voltage Control using Zero Voltage Crossing

Things used in this project

Hardware components

Arduino UNO

DIYables USB Cable 2.0 Type A/B for Arduino Uno

DIYables Jumper Wires

Software apps and online services

Arduino IDE

Story

Usually, our home appliances run on single-phase AC voltage. And in India usually, a house is supplied with single-phase AC voltage with a voltage range of about 220-240 volts at 50Hz(your supply may be different). AC voltage in its first half cycle starts increasing the voltage from 0 to 220-240 as its peak voltage and when it reaches the peak voltage it starts decreasing from 220-240 to 0. Now in the next half cycle, the voltage starts increasing but in the negative direction and ultimately reaches to its peak (say -220v-240v) and again it will start decreasing and continue to reach zero voltage.

If we draw a graph of this voltage nature with respect to time. We will find it as a sine wave. So, in India, the supplied voltage is a sine wave with a 220-240v peak and a frequency of 50Hz. (check with your country's supply voltage range)

Now controlling AC voltage means we are trying to control the speed of single phase ac motor or trying to control the brightness of an incandescent bulb or any other task which needs to control the AC voltage. So, to control the voltage we can not chop off the required voltage. First, we need to know the zero point of the voltage which means to detect the AC voltage when it reaches the zero point. And when we get the zero point at that time we can chop the voltage as required. To detect zero voltage crossing we will need a zero voltage crossing detector.

This is the main circuit of the project and needs to design it very carefully.

Here we have a 12-0 transformer which step down the 220 AC voltage to 12v. This 12v AC is fed to the full bridge rectifier circuit. As shown in the figure. And pin number 5 of the optocoupler(4N25) is connected to pin number 2 of the Arduino UNO board. Arduino UNO has two interrupt pins. Pin numbers 2 and 3 are the two interrupt pins. Here we are using pin 2. Read more.

OPTOCOUPLER or OPTO ISOLATER(4N25):

It is made up of a LED and a phototransistor. Its internal construction is shown in the figure. So whenever AC is at the proper voltage the output at pin number 5 is LOW. And when it crosses through the ZERO point, LED in the IC goes OFF and a HIGH pulse is generated at pin 5. And this HIGH pulse is used to trigger the interrupt(INT0) pin and the circuit is activated. Read more.

OPTOCOUPLER or OPTO ISOLATOR (MOC3021):

Its internal construction is shown in the figure.

Pin 1 and 2 are the anode and cathode of LED respectively. That means the voltage at pin 1 will decide the brightness of the LED and so the voltage across the thyristor. Pins 4 and 6 are used to trigger the gate of TRIAC(BT136). Read more.

Circuit used to control the voltage across the TRIAC pin as shown.

TRIAC(BT136) – TRIAC is a bidirectional triode thyristor/ bilateral triode thyristor. It is a three-terminal electronic component that conducts current in either direction when triggered from the gate terminal. Read more.

Hardware Required:

Follow the link for the complete component list. HERE

Software Requirements:

Arduino IDE (Download Link HERE)

Block Diagram:

Circuit Diagram:

According to the above circuit diagram the major components of the circuit are:

Arduino Board
Power Supply
Variable Resistor
ON-OFF Switch

The Arduino Board is the programmable unit that will be controlling the entire functionality of the circuit and every module will be interfaced with it.

Power Supply: Arduino UNO required 5v DC voltage and it is provided by the USB cable itself. If you want to make it a standalone project you can use an external power supply which is designed with a voltage regulator 7805.

Variable Resistor: A 10K ohm variable resistor is used to change the firing angle. One end of the resistor is connected to GND and the other to VCC and the third/middle/output pin is connected to the A0 pin of Arduino UNO.

ON-OFF Switch: Here you can use a toggle pin to start and stop. This switch is connected to pin number 7 of Arduino UNO. I am connecting this pin directly to GRND.

For a video tutorial click here.

AC voltage control Source code

#define triacPulse 10
#define SW 7

int x=0;
void setup(){
   pinMode(2, INPUT);
   digitalWrite(2, INPUT_PULLUP); // pull up
   pinMode(triacPulse, OUTPUT);
   pinMode(SW, INPUT);
   digitalWrite(SW, INPUT_PULLUP);
    }

void loop() {
 
  if (!digitalRead(SW)){ // When the switch is closed
    x=analogRead(A0);
    attachInterrupt(0, acon, FALLING); // attach Interrupt at PIN2
    }  
  else if (digitalRead(SW)){ 
       detachInterrupt(0); // Detach Interrupt
     } 
  } 

void acon()  
   {
    delayMicroseconds((analogRead(A0) * 7) + 200); // read AD0 
    digitalWrite(triacPulse, HIGH);
    delayMicroseconds(50);  //delay 50 uSec on output pulse to turn on triac  
    digitalWrite(triacPulse, LOW);
   }

Credits

MyEngineeringStuffs

13 projects • 71 followers

I 😍 to help people, students are always FIRST, and Yes👉https://paypal.me/pawanbehera1 you can buy me a COFFEE if U😍 my WORK, NAMASTE 🙏

Arduino Based AC Voltage Control using Zero Voltage Crossing

Things used in this project

Hardware components

Software apps and online services

Story

Circuit used to control the voltage across the TRIAC pin as shown.

Code

AC voltage control Source code

Credits

MyEngineeringStuffs

Comments

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Arduino Based AC Voltage Control using Zero Voltage Crossing

Arduino Based AC Voltage Control using Zero Voltage Crossing

Things used in this project

Hardware components

Software apps and online services

Story

Circuit used to control the voltage across the TRIAC pin as shown.

Code

AC voltage control Source code

Credits

MyEngineeringStuffs

Comments

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