Circuit Documentation

Summary

The circuit in question is a multifunctional sensor and communication system that utilizes an Arduino 101 as the central processing unit. It interfaces with various sensors including a DHT11 temperature and humidity sensor, an MQ2 gas sensor, a flow rate sensor, and a PH meter. For wireless communication, it employs an ESP8266 NodeMCU and a LoRa Ra-02 SX1278 module. The circuit is designed to collect environmental data and transmit it over LoRa and ESP8266 networks.

Component List

Arduino 101

• Microcontroller board based on the Intel Curie
• Provides a wide range of I/O pins for interfacing with various sensors and modules

DHT11 Sensor V2

• A basic, ultra low-cost digital temperature and humidity sensor
• Uses a capacitive humidity sensor and a thermistor to measure the surrounding air

LoRa Ra-02 SX1278

• A long-range transceiver module based on the SX1278
• Operates at 433MHz and capable of transmitting data over long distances

ESP8266 NodeMCU

• A low-cost Wi-Fi microchip with full TCP/IP stack and microcontroller capability
• Used for Wi-Fi communication and internet connectivity

MQ2

• A gas sensor used for detecting a variety of gases including LPG, smoke, and alcohol vapor
• Has both digital and analog outputs

Flow Rate Sensor

• Measures the rate of fluid flow
• Typically used in irrigation systems, water conservation systems, etc.

PH Meter

• Measures the acidity or alkalinity of a solution
• Important for environmental monitoring and chemical analysis

Wiring Details

Arduino 101

• 3V3 connected to ESP8266 NodeMCU 3V3 and LoRa Ra-02 SX1278 3.3V
• GND connected to PH Meter GND
• 5V connected to PH Meter VCC
• D7 connected to DHT11 Sensor V2 DAT
• D13/SCK, D12/MISO, D11 PWM/MOSI, D10 PWM/SS connected to corresponding SPI pins on LoRa Ra-02 SX1278
• D9 PWM connected to LoRa Ra-02 SX1278 RST
• D8 connected to LoRa Ra-02 SX1278 DI00
• D6 PWM connected to MQ2 DOUT
• D5 PWM connected to Flow Rate Sensor Digital pin
• D1/TX connected to ESP8266 NodeMCU RX
• D0/RX connected to ESP8266 NodeMCU TX
• A0 connected to MQ2 AOUT
• A2 connected to PH Meter Signal

DHT11 Sensor V2

• GND connected to common ground net
• VCC connected to common VCC net

LoRa Ra-02 SX1278

• GND connected to common ground net
• SPI pins connected to corresponding Arduino 101 pins

ESP8266 NodeMCU

• GND connected to common ground net
• 3V3 connected to Arduino 101 3V3

MQ2

• GND connected to common ground net
• VCC connected to common VCC net
• AOUT connected to Arduino 101 A0
• DOUT connected to Arduino 101 D6 PWM

Flow Rate Sensor

• GND connected to common ground net
• Positive connected to common VCC net
• Digital pin connected to Arduino 101 D5 PWM

PH Meter

• GND connected to common ground net
• VCC connected to Arduino 101 5V
• Signal connected to Arduino 101 A2

Documented Code

Arduino 101 Code

#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <Adafruit_Sensor.h>
#include <DHT.h>
#include <RTClib.h>
#include <SPI.h>
#include <LoRa.h>
#include <SoftwareSerial.h>

// LCD Setup
LiquidCrystal_I2C lcd(0x27, 16, 2);

// DHT Sensor Setup
#define DHTPIN 7
#define DHTTYPE DHT11
DHT dht(DHTPIN, DHTTYPE);

// Dust Sensor Setup
#define measurePin A0
#define ledPower 7
int samplingTime = 280;
int deltaTime = 40;
int sleepTime = 9680;
float voMeasured = 0;
float calcVoltage = 0;
float dustDensity = 0;

// RTC Setup
RTC_DS1307 rtc;

// LoRa and ESP8266 Setup
#define NSS  10
#define RST  9
#define DIO0 8
SoftwareSerial espSerial(0, 1);  // RX, TX for ESP8266

// Buzzer Setup
const int buzzer = 9;

// Variables
int num = 0;

void setup() {
  Serial.begin(115200);

  // LCD Init
  lcd.init();
  lcd.backlight();

  // DHT Init
  dht.begin();

  // RTC Init
  if (!rtc.begin()) {
    Serial.println("Couldn't find RTC");
    while (1);
  }

  // LoRa Init
  LoRa.setPins(NSS, RST, DIO0);
  if (!LoRa.begin(433E6)) {
    Serial.println("Starting LoRa failed!");
    while (1);
  }

  // ESP8266 Init
  espSerial.begin(9600);

  // Buzzer Init
  pinMode(buzzer, OUTPUT);

  // Dust Sensor Init
  pinMode(ledPower, OUTPUT);

  // Initial Display on LCD
  lcd.setCursor(0, 0);
  lcd.print("System Starting");
  delay(2000);
}

void loop() {
  // Time from RTC
  DateTime now = rtc.now();

  // Temperature and Humidity from DHT
  float h = dht.readHumidity();
  float t = dht.readTemperature();

  // Dust Sensor Reading
  digitalWrite(ledPower, LOW);
  delayMicroseconds(samplingTime);
  voMeasured = analogRead(measurePin);
  delayMicroseconds(deltaTime);
  digitalWrite(ledPower, HIGH);
  delayMicroseconds(sleepTime);
  calcVoltage = voMeasured * (5.0 / 1024.0);
  dustDensity = 170 * calcVoltage - 0.1;

  // Buzzer Alert
  tone(buzzer, 1000);
  delay(1000);
  noTone(buzzer);
  delay(1000);

  // Display on LCD
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Time: ");
  lcd.print(now.hour());
  lcd.print(":");
  lcd.print(now.minute());
  lcd.print(":");
  lcd.print(now.second());

  lcd.setCursor(0, 1);
  lcd.print("Temp: ");
  lcd.print(t);
  lcd.print(" C");

  lcd.setCursor(0, 2);
  lcd.print("Humidity: ");
  lcd.print(h);
  lcd.print(" %");

  lcd.setCursor(0, 3);
  lcd.print("Dust: ");
  lcd.print(dustDensity);

  // LoRa Communication
  LoRa.beginPacket();
  LoRa.print("Data: Temp=");
  LoRa.print(t);
  LoRa.print(", Humidity=");
  LoRa.print(h);
  LoRa.print(", Dust=");
  LoRa.print(dustDensity);
  LoRa.endPacket();

  // ESP8266 Data Reception
  if (espSerial.available()) {
    String data = espSerial.readString();
    Serial.println("Data from ESP8266: " + data);
  }

  // Update every 2 seconds
  delay(2000);
}

DHT11 Sensor V2 Code

void setup() {
  // put your setup code here, to run once:

}

void loop() {
  // put your main code here, to run repeatedly:

}

(Note: The code for the DHT11 Sensor V2 is a placeholder and does not contain any functional code. It is likely that the actual sensor code is integrated within the Arduino 101 code.)