LCD 220V Mains Timer Circuit – Plug and Play Timer

In this post we are going to make an LCD 220 V mains operated timer using Arduino whose countdown time can be witnessed via 16 x 2 LCD display.

Introduction

The proposed LCD timer circuit is general purpose timer with display and few buttons for setting the time.

Once the time is set output goes high and starts countdown the time and when it reach 00:00:00 (Hour: Minute: Seconds) the output goes low. You may modify this project for your customized needs.

Now back to the project.

We always worry on our electrical or electronic devices which ran for too long just because we forget them to switch off them.

Time critical electrical and electronic devices like electric cooker, low profile battery chargers, heaters etc. need to be switched off at right moment otherwise we may end up reducing the life time of the gadgets or the processed end item such as food will be unpleasant to consume.

Low profile battery chargers might not have timer or battery monitoring system which might damage the battery’s life span if we left on charge for long time.

We can say hundreds of examples like these, to escape from such bad results a timer socket can be used.

A timer socket is a simple timer which is connected to AC socket and the time critical devices will be connected at output of the timer socket. The user has to input the time using button or dials for how long the connected devices should be powered.

Once the pre-set time is reached the device will be cut-off from the power supply.

The Design:

The proposed LCD socket timer project consists of Arduino which acts as brain of the project, a 16 x 2 LCD display which shows the remaining time, three buttons for setting the time and a relay for connecting and disconnecting the output AC supply.

Circuit Diagram:

The above circuit is the arduino to LCD display connection, a 10K potentiometer is provided for adjusting the contrast of the display. Rest of the above connections are self-explanatory.

The circuit needs power to operate so, a simple regulated power supply is provided; it can output constant 9V to arduino and relay.

S1, S2 and S3 are push buttons by which the user can set time. S1 is hour button S2 is minute button and S3 is start button.

A 1N4007 diode is connected across the relay terminal to absorb high voltage back EMF from the relay while switching.

Use at-least 5A relay and 5A output socket. Connect a 5A fuse at the input supply. Always use 3-pin plug at input; don’t skip earth wiring and don’t interchange Live and Neutral lines.

Circuit Layout: 

Program Code:

//-------Program Developed by R.GIRISH---------//
#include <LiquidCrystal.h>

LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

const int hbtn = A0;
const int mbtn = A1;
const int start = A2;
const int relay = 7;

unsigned int hrs = 0;
unsigned int Min = 0;
unsigned int sec = 60;

boolean Hrs = false;
boolean Minlt = true;

void setup() {
  lcd.begin(16, 2);

  pinMode(hbtn, INPUT_PULLUP);
  pinMode(mbtn, INPUT_PULLUP);
  pinMode(start, INPUT_PULLUP);
  pinMode(relay, OUTPUT);
  
  digitalWrite(relay, LOW);

  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Please set time:");
  lcd.setCursor(0, 1);
  lcd.print("Hour:00 Min:00");
}

void displayTime() {
  lcd.setCursor(0, 1);
  lcd.print("Hour:");
  if (hrs < 10) lcd.print('0');
  lcd.print(hrs);
  lcd.print(" Min:");
  if (Min < 10) lcd.print('0');
  lcd.print(Min);
}

void loop() {
  // Set hours
  if (digitalRead(hbtn) == LOW) {
    hrs++;
    Hrs = true;
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Please set time:");
    displayTime();
    delay(300);
  }

  // Set minutes
  if (digitalRead(mbtn) == LOW && Minlt) {
    Min++;
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Please set time:");
    displayTime();
    
    if (Min >= 60) {
      Minlt = false;
    }
    delay(300);
  }

  // Start countdown
  if (digitalRead(start) == LOW && (hrs != 0 || Min != 0)) {
    digitalWrite(relay, HIGH);

    // Adjust initial minute
    if (Min != 0) Min--;

    while (true) {
      lcd.clear();
      lcd.setCursor(5, 0);
      lcd.print(hrs);
      lcd.print(":");
      if (Min < 10) lcd.print('0');
      lcd.print(Min);
      lcd.print(":");
      if (sec < 10) lcd.print('0');
      lcd.print(sec);

      lcd.setCursor(0, 1);
      lcd.print(" AC OUTPUT: ON");

      delay(1000);
      sec--;

      if (hrs == 0 && Min == 0 && sec == 0) {
        digitalWrite(relay, LOW);
        lcd.clear();
        lcd.setCursor(5, 0);
        lcd.print("0:0:0");
        lcd.setCursor(0, 1);
        lcd.print(" AC OUTPUT: OFF");
        while (true) {}
      }

      if (sec == 0) {
        sec = 59;
        if (Min != 0) Min--;
      }

      if (Min == 0 && Hrs) {
        if (hrs != 0) {
          hrs--;
          Min = 59;
        } else {
          Hrs = false;
        }
      }
    }
  }
}
//-------Program Developed by R.GIRISH---------//

How to operate this LCD Socket Timer:

• Connect the LCD timer to 220 V AC mains and connect you device at output of the timer’s socket.

• It will display “Hours: 00 Min: 00”. Press the hour (S1) or minute (S2) buttons to set the time.

• Pressing the buttons will increment the count.

• Once you set the time, press start button (S3). The output turns ON.

• The output turns OFF when the display reads 0:0:0.

NOTE: The timer displays “60” instead of “00” for minutes and seconds, which is same as traditional timers and clock counts 00 to 59 for 60 seconds. Here the timer counts 1 to 60 for 60 seconds.
If you have any questions regarding this project feel free to express in the comment section.