Circuit Documentation

Summary

The circuit in question is designed to interface an Arduino UNO R4 WiFi microcontroller with a DHT11 temperature and humidity sensor and an LCD display. The LCD is used to display the temperature and humidity readings obtained from the DHT11 sensor. A rotary potentiometer is included to adjust the contrast of the LCD display. The Arduino board manages the sensor data acquisition and controls the LCD display to update the readings periodically.

Component List

DHT11

• Description: A basic, low-cost digital temperature and humidity sensor.
• Pins:
  • 5V: Power supply (5V)
  • S: Signal output to microcontroller
  • GND: Ground

LCD Display (16 pin)

• Description: A 16x2 character LCD display that shows alphanumeric characters.
• Pins:
  • VSS: Ground for the LCD
  • VDD: Power supply for the LCD (5V)
  • VO: Contrast adjustment
  • RS: Register Select
  • R_W: Read/Write (grounded for write only)
  • E: Enable pin
  • DB0 - DB7: Data lines (DB4-DB7 used for 4-bit mode)
  • A: Anode for backlight
  • K: Cathode for backlight

Arduino UNO R4 WiFi

• Description: A microcontroller board based on the ATmega328 with integrated WiFi.
• Pins:
  • GND: Ground
  • 5V: Power supply (5V)
  • D0 - D13: Digital I/O pins
  • A0 - A5: Analog input pins
  • RESET: Reset pin
  • Other pins not used in this circuit

Rotary Potentiometer

• Description: A three-terminal resistor with a rotating contact that forms an adjustable voltage divider.
• Pins:
  • leg1: Typically connected to a power source
  • wiper: The adjustable output voltage (connected to VO on the LCD)
  • leg2: Typically connected to ground
• Properties:
  • Resistance: 10,000 Ohms

Wiring Details

DHT11

• 5V to Arduino 5V
• S to Arduino D2
• GND to common ground

LCD Display (16 pin)

• VSS, R_W, K to common ground
• VDD, A to Arduino 5V
• VO to wiper of Rotary Potentiometer
• RS to Arduino D7
• E to Arduino D8
• DB4 to Arduino D9
• DB5 to Arduino D10
• DB6 to Arduino D11
• DB7 to Arduino D12

Rotary Potentiometer

• leg1 to Arduino 5V
• wiper to VO on the LCD
• leg2 to common ground

Arduino UNO R4 WiFi

• GND to common ground
• 5V to power components requiring 5V
• Digital pins D2, D7, D8, D9, D10, D11, D12 to respective components as detailed above

Documented Code

#include <DHT.h>
#include <LiquidCrystal.h>

// Initialize DHT sensor
#define DHTPIN 2     // DHT11 data pin connected to D2
#define DHTTYPE DHT11
DHT dht(DHTPIN, DHTTYPE);

// Initialize the LCD
const int rs = 7, en = 8, d4 = 9, d5 = 10, d6 = 11, d7 = 12;
LiquidCrystal lcd(rs, en, d4, d5, d6, d7);

void setup() {
  // Start the DHT sensor
  dht.begin();
  
  // Start the LCD
  lcd.begin(16, 2);
  lcd.print("Temp: ");
  lcd.setCursor(0, 1);
  lcd.print("Humidity: ");
}

void loop() {
  // Read temperature and humidity
  float h = dht.readHumidity();
  float t = dht.readTemperature();
  
  // Check if any reads failed and exit early (to try again).
  if (isnan(h) || isnan(t)) {
    lcd.setCursor(6, 0);
    lcd.print("Error");
    lcd.setCursor(10, 1);
    lcd.print("Error");
    return;
  }
  
  // Print temperature and humidity to LCD
  lcd.setCursor(6, 0);
  lcd.print(t);
  lcd.print(" C");
  lcd.setCursor(10, 1);
  lcd.print(h);
  lcd.print(" %");
  
  // Wait a few seconds between measurements.
  delay(2000);
}

This code initializes the DHT11 sensor and the LCD display, then enters a loop where it reads temperature and humidity from the DHT11 sensor and displays the values on the LCD. If the sensor fails to provide valid readings, an error message is displayed instead.