Monitoring and Protection an Ecological Area #8 - Adding Multiple Sensors: DS18B20, DHT22 and MQ-135

Table of Contents

1. Project Introduction
2. Getting Started
3. Communication Between Two MKR WAN 1300
4. LoRaWAN System Range Testing
5. Assembling and Adding LCD Display to the Transmitter
6. Assembling and Adding LCD Display to the Receiver
7. LoRaWAN´s Field Test with a DS18B20 Sensor
8. Adding Multiple Sensors: DS18B20, DHT22 and MQ-135
9. Modifying Receiver Code for Multiple Sensors
10. LoRaWAN´s Field Test with Multiple Sensors
11. Connecting LoRaWAN to an IoT Provider through the Arduino NANO 33 IoT
12. LoRaWAN and IoT Connection with a DS18B20 Sensor
13. Testing LoRaWAN and IoT Connection with a DS18B20 Sensor
14. LoRaWAN and IoT Connection with Multiple Sensors
15. Testing LoRaWAN and IoT Connection with Multiple Sensors
16. Project Report Updated

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 Adding Multiple Sensors: DS18B20, DHT22 and MQ-135

Transmitter Schematic Diagram

In the figure below I show you the electrical diagram of the transmitter after adding the DHT22 humidity sensor and the MQ-135 air quality sensor.

Adding the DHT22 Sensor

In the figure below I show you the DHT22 sensor.

In this sensor I only obtain humidity readings with value ranges between 0 to 100%. I omit the temperature readings as the DS18B20 temperature sensor has a better measurement range (-55°C to +125°C). You can get the library used to program this sensor here: DHT-sensor-library

Adding the MQ-135 Sensor

In the figure below I show you the MQ-135 sensor.

Sensitive material of gas sensor is SnO2, which with lower conductivity in clean air. When target pollution gas exists, the sensor’s conductivity gets higher along with the gas concentration rising. Users can convert the change of conductivity to correspond output signal of gas concentration through a simple circuit.

I use this sensor to detect and measure carbon dioxide (CO2) particles in parts per million (ppm). In the following links you can find the reference information and the code to obtain it:

https://github.com/5cottyD/Projects/blob/master/co2ppm_meter.ino

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Monitoring and Protection an Ecological Area #8 - Adding Multiple Sensors: DS18B20, DHT22 and MQ-135

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Since these sensors have small differences, I made a small adjustment to this code to calibrate the CO2 level to 0. This is done in the following line of code:

#define co2Zero 55 //calibrated CO2 0 level

After mounting the three sensors, the device would look like the image below.

Transmitter code

After adding the DHT22 and MQ-135 sensors, the transmitter code would be as shown below:

LoRaSender_v3.ino

// AUTHOR: GUILLERMO PEREZ GUILLEN

#include <SPI.h> // LoRa->
#include <LoRa.h>
#include <OneWire.h> // DS18B20->               
#include <DallasTemperature.h>
#include <Wire.h> // LCD->
#include "rgb_lcd.h"
rgb_lcd lcd;
const int colorR = 173;
const int colorG = 255;
const int colorB = 47;

#include "DHT.h" // DHT22 ->
#define DHTPIN 3    // Pin where the sensor is connected
#define DHTTYPE DHT22   // DHT22 sensor
DHT dht(DHTPIN, DHTTYPE);

// DS18B20-> Data wire is plugged into port 2 on the Arduino
#define ONE_WIRE_BUS 2
OneWire oneWire(ONE_WIRE_BUS);
DallasTemperature sensors(&oneWire); 

#define anInput     A0 // MQ135-> analog feed from MQ135
#define co2Zero     0 // calibrated CO2 0 level

int counter = 0;

void setup() {
  // set up the LCD's number of columns and rows:
  lcd.begin(16, 2);
  lcd.setRGB(colorR, colorG, colorB);
  lcd.print("ECOLOGY!");  
  pinMode(anInput,INPUT); // MQ135 
  lcd.setCursor(0, 1); // LCD 
  lcd.print("LoRa Sender");
  if (!LoRa.begin(915E6)) {
  lcd.setCursor(0, 1); // LCD 
  lcd.print("Starting LoRa failed!");    
    while (1);
  }
  sensors.begin();   
  dht.begin();
}

void loop() {
  int co2now[10]; //int array for co2 readings
  int co2raw = 0; //int for raw value of co2
  int co2ppm = 0; //int for calculated ppm
  int zzz = 0; //int for averaging
  for (int x = 0;x<10;x++) // MQ135-> samplpe co2 10x over 2 seconds
  {                   
    co2now[x]=analogRead(A0);
    delay(200);
  }
  for (int x = 0;x<10;x++) // add samples together
  {                     
    zzz=zzz + co2now[x];  
  }  
  co2raw = zzz/10; // divide samples by 10
  co2ppm = co2raw - co2Zero; // get calculated ppm
  if (co2ppm <= 0) {
    co2ppm = 1;
  }
  else {
    co2ppm = co2ppm;
  }     
  int h = dht.readHumidity(); //We read the Humidity
  sensors.requestTemperatures();   //The command to read the temperature is sent
  int temp = sensors.getTempCByIndex(0); //The temperature is obtained in ยบC 
  // send packet
  LoRa.beginPacket();
  LoRa.print(temp);
  LoRa.print(",");
  LoRa.print(h);  
  LoRa.print(",");
  LoRa.print(co2ppm);
  LoRa.endPacket();
  // LCD display data
  lcd.clear();
  lcd.setCursor(0, 0); // LCD 
  lcd.print("P=");
  lcd.setCursor(3, 0); // LCD 
  lcd.print(counter);
  lcd.setCursor(8, 0); // LCD 
  lcd.print("T=");  
  lcd.setCursor(11, 0); // LCD 
  lcd.print(temp);
  lcd.setCursor(14, 0); // LCD 
  lcd.print("C");
  lcd.setCursor(0, 1); // LCD 
  lcd.print("H=");
  lcd.setCursor(3, 1); // LCD 
  lcd.print(h);   
  lcd.setCursor(6, 1); // LCD 
  lcd.print("%");
  lcd.setCursor(8, 1); // LCD 
  lcd.print("CO2="); 
  lcd.setCursor(13, 1); // LCD 
  lcd.print(co2ppm);
  counter++;   
  delay(2000);
}

Analysis:

As you can see, the data from the three sensors is separated by a comma(",").

  // send packet
  LoRa.beginPacket();
  LoRa.print(temp);
  LoRa.print(",");
  LoRa.print(h);  
  LoRa.print(",");
  LoRa.print(co2ppm);
  LoRa.endPacket();

Download section:

• You can get the code from this post below:

adding_multiple_sensors_dsS18B20_dht22_and_mq135.zip