Circuit Documentation

Summary

This circuit integrates various sensors and modules with a NodeMCU V3 ESP8266 microcontroller to monitor environmental parameters such as gas levels, temperature, humidity, and heart rate. The data is displayed on an OLED screen and can be communicated via a GSM module. The circuit also includes a relay and a servo motor for additional control functionalities.

Component List

1. MQ-2 Gas Sensor

   • Description: Detects gas levels in the environment.
   • Pins: GND, VCC, ANALOG, Digital

2. NodeMCU V3 ESP8266

   • Description: Microcontroller with Wi-Fi capabilities.
   • Pins: A0, GND, VU, S3, S2, S1, SC, S0, SK, 3V3, EN, RST, Vin, D0, D1, D2, D3, D4, D5, D6, D7, D8, RX, TX

3. OLED 1.3" Display

   • Description: Displays data visually.
   • Pins: GND, VCC, SCL, SDA

4. MLX90614 Temperature Sensor

   • Description: Measures ambient and object temperatures.
   • Pins: SDA, SCL, GND, VIN

5. DS3231 RTC

   • Description: Real-time clock module.
   • Pins: 32K, SQW, SCL, SDA, VCC, GND

6. DHT11 Humidity and Temperature Sensor

   • Description: Measures humidity and temperature.
   • Pins: VDD, DATA, NULL, GND

7. SIM800L GSM Module

   • Description: GSM module for communication.
   • Pins: 5V, GND, VDD, SIM_TXD, SIM_RXD, RST

8. MAX30102 Heart Rate and Oxygen Sensor

   • Description: Measures heart rate and blood oxygen levels.
   • Pins: VIN, SCL, SDA, INT, IRQ, RD, GND

9. 1 Channel Relay 5V

   • Description: Controls high voltage devices.
   • Pins: VCC, GND, IN, NC, COM, NO

10. Servo (Wokwi Compatible)

    • Description: Servo motor for mechanical movement.
    • Pins: GND, V+, PWM

Wiring Details

MQ-2 Gas Sensor

• GND: Connected to NodeMCU GND
• VCC: Connected to NodeMCU Vin
• ANALOG: Connected to NodeMCU A0

NodeMCU V3 ESP8266

• A0: Connected to MQ-2 ANALOG
• 3V3: Connected to OLED VCC, DHT11 VDD, MAX30102 VIN, Relay VCC
• GND: Connected to OLED GND, DHT11 GND, MAX30102 GND, Relay GND, MQ-2 GND, MLX90614 GND, DS3231 GND, SIM800L GND, Servo GND
• Vin: Connected to MQ-2 VCC, MLX90614 VIN, DS3231 VCC, SIM800L 5V, Servo V+
• D1: Connected to MAX30102 SCL, MLX90614 SCL, OLED SCL, DS3231 SCL
• D2: Connected to MAX30102 SDA, MLX90614 SDA, OLED SDA, DS3231 SDA
• D4: Connected to DHT11 DATA
• D5: Connected to Servo PWM
• D6: Connected to SIM800L SIM_RXD
• D7: Connected to Relay IN, SIM800L SIM_TXD

OLED 1.3" Display

• GND: Connected to NodeMCU GND
• VCC: Connected to NodeMCU 3V3
• SCL: Connected to NodeMCU D1
• SDA: Connected to NodeMCU D2

MLX90614 Temperature Sensor

• SDA: Connected to NodeMCU D2
• SCL: Connected to NodeMCU D1
• GND: Connected to NodeMCU GND
• VIN: Connected to NodeMCU Vin

DS3231 RTC

• SCL: Connected to NodeMCU D1
• SDA: Connected to NodeMCU D2
• VCC: Connected to NodeMCU Vin
• GND: Connected to NodeMCU GND

DHT11 Humidity and Temperature Sensor

• VDD: Connected to NodeMCU 3V3
• DATA: Connected to NodeMCU D4
• GND: Connected to NodeMCU GND

SIM800L GSM Module

• 5V: Connected to NodeMCU Vin
• GND: Connected to NodeMCU GND
• SIM_TXD: Connected to NodeMCU D7
• SIM_RXD: Connected to NodeMCU D6

MAX30102 Heart Rate and Oxygen Sensor

• VIN: Connected to NodeMCU 3V3
• SCL: Connected to NodeMCU D1
• SDA: Connected to NodeMCU D2
• GND: Connected to NodeMCU GND

1 Channel Relay 5V

• VCC: Connected to NodeMCU 3V3
• GND: Connected to NodeMCU GND
• IN: Connected to NodeMCU D7

Servo (Wokwi Compatible)

• GND: Connected to NodeMCU GND
• V+: Connected to NodeMCU Vin
• PWM: Connected to NodeMCU D5

Documented Code

#include <Wire.h>
#include <Adafruit_SSD1306.h>
#include <Adafruit_MLX90614.h>

// OLED Display Settings
#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);

// MLX90614 Sensor
Adafruit_MLX90614 mlx = Adafruit_MLX90614();

// MQ-2 Sensor Pin
#define MQ2_PIN A0

// Thresholds for gas levels
#define GAS_SAFE_THRESHOLD 300
#define GAS_WARNING_THRESHOLD 700

void setup() {
  // Initialize Serial Communication
  Serial.begin(115200);

  // Initialize OLED Display
  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) { // Corrected initialization
    Serial.println(F("SSD1306 allocation failed"));
    for (;;); // Loop forever if display initialization fails
  }
  display.clearDisplay();
  display.display();

  // Initialize MLX90614
  if (!mlx.begin()) {
    Serial.println("Error connecting to MLX90614 sensor!");
    while (1);
  }

  // Display Welcome Screen
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
  display.setCursor(0, 0);
  display.println("MQ-2 & MLX90614");
  display.println("Initializing...");
  display.display();
  delay(2000);
  display.clearDisplay();
}

void loop() {
  // Read Analog Value from MQ-2
  int gasValue = analogRead(MQ2_PIN);

  // Read Temperature from MLX90614
  float ambientTemp = mlx.readAmbientTempC();
  float objectTemp = mlx.readObjectTempC();

  // Print Readings to Serial Monitor
  Serial.print("MQ-2 Gas Reading: ");
  Serial.println(gasValue);
  Serial.print("Ambient Temp: ");
  Serial.print(ambientTemp);
  Serial.println(" °C");
  Serial.print("Object Temp: ");
  Serial.print(objectTemp);
  Serial.println(" °C");

  // Update OLED Display
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
  display.setCursor(0, 0);
  display.println("Gas & Temp Readings:");

  // Display Gas Data
  display.setTextSize(1);
  display.setCursor(0, 10);
  display.print("Gas: ");
  display.print(gasValue);

  // Display Gas Status
  display.setCursor(0, 20);
  if (gasValue < GAS_SAFE_THRESHOLD) {
    display.println(" (Safe)");
  } else if (gasValue < GAS_WARNING_THRESHOLD) {
    display.println(" (Warning)");
  } else {
    display.println(" (Danger!)");
  }

  // Display Temperature Data
  display.setCursor(0, 35);
  display.print("Amb Temp: ");
  display.print(ambientTemp);
  display.println("C");

  display.setCursor(0, 45);
  display.print("Obj Temp: ");
  display.print(objectTemp);
  display.println("C");

  // Refresh Display
  display.display();

  // Delay before next reading
  delay(1000);
}