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Wi-Fi Controlled Temperature Monitoring System with OLED Display

Image of Wi-Fi Controlled Temperature Monitoring System with OLED Display

Circuit Documentation

Summary

This circuit is designed to monitor temperature using an LM35 temperature sensor and control a fan based on the temperature readings. The ESP32 microcontroller processes the sensor data and drives a TRIAC to control the fan's power. An OLED display is used to show the current temperature and fan speed. The circuit also includes a MOC3041 optoisolator for safe interfacing with the TRIAC, and a BT139 for controlling the AC load.

Component List

1. ESP32 (30 pin)

  • Description: A powerful microcontroller with built-in Wi-Fi and Bluetooth capabilities.
  • Purpose: Acts as the main controller for the circuit, processing sensor data and controlling the fan.

2. 0.96" OLED

  • Description: A small OLED display for visual output.
  • Purpose: Displays the current temperature and fan speed.

3. 120V Outlet

  • Description: A standard electrical outlet for AC power.
  • Purpose: Provides power to the fan and other AC components.

4. MOC3041

  • Description: An optoisolator with a built-in TRIAC.
  • Purpose: Isolates the microcontroller from the high voltage AC circuit while controlling the TRIAC.

5. Temperature Sensor (LM35)

  • Description: An analog temperature sensor.
  • Purpose: Measures the ambient temperature and provides an output voltage proportional to the temperature.

6. BT139 600

  • Description: A TRIAC for controlling AC loads.
  • Purpose: Switches the fan on and off based on the control signal from the microcontroller.

7. 220 Fan

  • Description: A fan that operates on 220V AC.
  • Purpose: Provides cooling based on temperature readings.

8. Resistors

  • Description: Passive components that limit current flow.
  • Purpose: Used in various parts of the circuit for current limiting and voltage division.

9. Ceramic Capacitor

  • Description: A capacitor used for filtering and stability.
  • Purpose: Provides stability in the circuit by filtering out noise.

10. 5A Fuse

  • Description: A safety device that protects the circuit from overcurrent.
  • Purpose: Prevents damage to the circuit components by breaking the circuit in case of excessive current.

Wiring Details

ESP32 (30 pin)

  • D34 connected to Vout of Temperature Sensor (LM35)

  • D12 connected to ANODE of MOC3041

  • GND connected to GND of 0.96" OLED

  • Vin connected to VDD of 0.96" OLED

  • D22 connected to SCK of 0.96" OLED

  • D21 connected to SDA of 0.96" OLED

  • GND connected to CATHODE of MOC3041

  • 3V3 connected to +Vs of Temperature Sensor (LM35)

0.96" OLED

  • GND connected to GND of ESP32

  • VDD connected to Vin of ESP32

  • SCK connected to D22 of ESP32

  • SDA connected to D21 of ESP32

120V Outlet

  • AC Neutral connected to output of 5A fuse

  • AC Hot connected to MT1 of BT139 600

  • pin2 of Resistor connected to AC Hot of 120V Outlet

  • pin2 of Resistor connected to MT2 of BT139 600

MOC3041

  • TRIAC1 connected to pin1 of Resistor

  • CATHODE connected to GND of ESP32

Temperature Sensor (LM35)

  • GND connected to GND of ESP32

  • +Vs connected to 3V3 of ESP32

  • Vout connected to D34 of ESP32

BT139 600

  • GATE connected to pin2 of Resistor

  • MT1 connected to AC Hot of 120V Outlet

  • MT2 connected to pin2 of Resistor

220 Fan

  • N connected to input of 5A fuse

  • L connected to pin2 of Resistor

Resistors

  • Resistor 1 (360 Ohms):

    • pin1 connected to pin1 of Ceramic Capacitor
    • pin2 connected to TRIAC1 of MOC3041

  • Resistor 2 (330 Ohms):

    • pin1 connected to pin1 of Ceramic Capacitor
    • pin2 connected to L of 220 Fan

  • Resistor 3 (360 Ohms):

    • pin1 connected to pin1 of MOC3041
    • pin2 connected to GND of ESP32

Documented Code

#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

#define SCREEN_WIDTH 128  // OLED display width, in pixels
#define SCREEN_HEIGHT 64  // OLED display height, in pixels

// Declaration for an SSD1306 display connected to I2C (SDA, SCL pins)
#define OLED_RESET -1  // Reset pin (or -1 if sharing Arduino reset pin)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

#define LM35_PIN 34          // ESP32 analog input pin connected to LM35
#define TRIAC_PIN 12         // Pin controlling the TRIAC (GPIO 12)
#define ZERO_CROSS_PIN 13    // Pin connected to zero-cross detector (GPIO 13)
#define FAN_MAX_DELAY 8333   // Max delay in microseconds (100% off at 60Hz)

// Baseline temperature in °C (adjust this to your desired baseline)
float baselineTemp = 20.0;
int delayTime = 0;  // Delay for phase angle control

void IRAM_ATTR zeroCrossDetected() {
  delayMicroseconds(delayTime);
  digitalWrite(TRIAC_PIN, HIGH);  // Fire the TRIAC
  delayMicroseconds(10);          // Keep TRIAC on for a few microseconds
  digitalWrite(TRIAC_PIN, LOW);   // Turn off the TRIAC
}

void setup() {
  pinMode(TRIAC_PIN, OUTPUT);
  pinMode(ZERO_CROSS_PIN, INPUT);

  // Attach interrupt for zero-cross detection
  attachInterrupt(digitalPinToInterrupt(ZERO_CROSS_PIN), zeroCrossDetected, RISING);

  Serial.begin(115200);  // ESP32 operates faster, so use a higher baud rate
  
  // Initialize the OLED display
  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {  // Address 0x3C for most OLEDs
    Serial.println(F("SSD1306 allocation failed"));
    for (;;);  // Don't proceed, loop forever
  }
  display.clearDisplay();  // Clear the buffer
  display.setTextSize(4);  // Set text size (increase for bigger text)
  display.setTextColor(SSD1306_WHITE);  // Set text color
  
  delay(2000);  // Give display some time to initialize
}

void loop() {
  int sensorValue = analogRead(LM35_PIN);  // Read analog value from LM35
  
  // Convert the analog value to temperature in Celsius
  // LM35 outputs 10mV per degree Celsius, powered at 5V
  float voltage = sensorValue * (5.0 / 4095.0);  // Convert analog reading to voltage at 5V
  int currentTemp = (int)(voltage * 100);  // Convert voltage to temperature in Celsius as whole number

  // Display the temperature in the Serial Monitor
  Serial.print("Current Temp: ");
  Serial.println(currentTemp);

  // Display the temperature on the OLED
  display.clearDisplay();  // Clear the display each loop
  display.setCursor(0, 0);  // Start at top-left corner
  display.setTextSize(2);   // Set text size
  display.print("Temp: ");
  display.print(currentTemp); // Show only whole degrees
  display.println(" C");

  // Display fan speed (based on the delay time)
  float fanSpeed = map(delayTime, FAN_MAX_DELAY, 0, 0, 100);  // Calculate fan speed as percentage
  display.print("Fan: ");
  display.print((int)fanSpeed); // Show fan speed as whole number
  display.println(" %");

  display