Circuit Documentation

Summary

This circuit consists of an Arduino UNO microcontroller, an LCD I2C Display, and a 4-channel relay module. The Arduino UNO controls the relays and communicates with the LCD display via the I2C protocol. The LCD displays a welcome message and the frequency of a square wave generated on one of the relay control pins. The relays can be controlled via digital pins D3, D4, D5, and D6 on the Arduino.

Component List

1. Arduino UNO

   • Description: A microcontroller board based on the ATmega328P.
   • Pins: UNUSED, IOREF, Reset, 3.3V, 5V, GND, Vin, A0, A1, A2, A3, A4, A5, SCL, SDA, AREF, D13, D12, D11, D10, D9, D8, D7, D6, D5, D4, D3, D2, D1, D0

2. LCD I2C Display

   • Description: A 16x2 character LCD display with I2C interface.
   • Pins: GND, VCC, SDA, SCL

3. Relay 4 Channel 5v

   • Description: A 4-channel relay module that can be controlled by a 5V signal.
   • Pins: GND, IN1, IN2, IN3, IN4, VCC, COM1, COM2, COM3, COM4, NO1, NO2, NO3, NO4, NC1, NC2, NC3, NC4

Wiring Details

Arduino UNO

• GND is connected to:

  • GND of LCD I2C Display
  • GND of Relay 4 Channel 5v

• 3.3V is connected to VCC of LCD I2C Display

• A4 is connected to SDA of LCD I2C Display

• A5 is connected to SCL of LCD I2C Display

• D6 is connected to IN1 of Relay 4 Channel 5v

• D5 is connected to IN2 of Relay 4 Channel 5v

• D4 is connected to IN3 of Relay 4 Channel 5v

• D3 is connected to IN4 of Relay 4 Channel 5v

• 5V is connected to VCC of Relay 4 Channel 5v

LCD I2C Display

• GND is connected to GND of Arduino UNO

• VCC is connected to 3.3V of Arduino UNO

• SDA is connected to A4 of Arduino UNO

• SCL is connected to A5 of Arduino UNO

Relay 4 Channel 5v

• GND is connected to GND of Arduino UNO

• IN1 is connected to D6 of Arduino UNO

• IN2 is connected to D5 of Arduino UNO

• IN3 is connected to D4 of Arduino UNO

• IN4 is connected to D3 of Arduino UNO

• VCC is connected to 5V of Arduino UNO

• NO3 is connected to COM1 of Relay 4 Channel 5v

Code Documentation

/*
 * This Arduino Sketch initializes an I2C LCD display and controls a 4-channel
 * relay module. The LCD displays a welcome message and then continuously
 * updates to show the frequency of a square wave generated on one of the
 * relay control pins. The relays can be controlled via digital pins D3, D4,
 * D5, and D6.
 */

#include <Wire.h>
#include <LiquidCrystal_I2C.h>

// Initialize the LCD with I2C address 0x27 and 16x2 display
LiquidCrystal_I2C lcd(0x27, 16, 2);

// Relay control pins
const int relay1 = 6;
const int relay2 = 5;
const int relay3 = 4;
const int relay4 = 3;

// Frequency measurement variables
unsigned long previousMillis = 0;
const long interval = 1000; // Interval for frequency calculation (1 second)
int frequency = 0;

void setup() {
  // Initialize the LCD
  lcd.begin(16, 2); // Corrected to include the number of columns and rows
  lcd.backlight();
  lcd.setCursor(0, 0);
  lcd.print("Welcome!");
  lcd.setCursor(0, 1);
  lcd.print("Relay Control");
  delay(2000); // Display welcome message for 2 seconds

  // Set relay pins as outputs
  pinMode(relay1, OUTPUT);
  pinMode(relay2, OUTPUT);
  pinMode(relay3, OUTPUT);
  pinMode(relay4, OUTPUT);

  // Initialize relays to off
  digitalWrite(relay1, LOW);
  digitalWrite(relay2, LOW);
  digitalWrite(relay3, LOW);
  digitalWrite(relay4, LOW);
}

void loop() {
  unsigned long currentMillis = millis();

  // Generate square wave on relay1 pin
  digitalWrite(relay1, HIGH);
  delay(500); // 500ms HIGH
  digitalWrite(relay1, LOW);
  delay(500); // 500ms LOW

  // Calculate frequency every second
  if (currentMillis - previousMillis >= interval) {
    previousMillis = currentMillis;
    frequency = 1; // Frequency is 1 Hz (1 cycle per second)

    // Update LCD with frequency
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Frequency:");
    lcd.setCursor(0, 1);
    lcd.print(frequency);
    lcd.print(" Hz");
  }
}

This code initializes the LCD display and sets up the relay control pins. In the setup function, the LCD displays a welcome message, and the relay pins are set as outputs and initialized to the off state. The loop function generates a square wave on the first relay pin and updates the LCD with the frequency of the square wave every second.