Arduino with two DS18B20 temperature sensors

 

Introduction

Sometimes it is just convenient to have 2 temperature sensors able to display at the same time the temperature measured at two different places. For instance when an electronic circuit is in a phase of testing you may want to check both ambiant and the temperature at a component you suspect to dissipate heat excessively. It is easy to connect 2 of the sensors DS18B20 on the same one wire Dallas bus. This is this property which is being demonstrated in this project. The display is a LCD TFT 1.44” 128x128 with SPI driver ILI9163 and used with the Arduino Adafruit GFX library.














For more details see previous blog
https://lazarduino.blogspot.com/2019/02/arduino-thermometer-with-oled-display.html


DS18B20 Sensor wiring

Arduino code

/******TFT_ILI9163C_2xDS18B20_SL02**************
*   reads two DS18B20 temperature sensors
*   displays the two temperatures value on TFT_ILI9163C
*   slazare 2019 06 12
*/
#include <SPI.h>
#include <Adafruit_GFX.h>
#include <TFT_ILI9163C.h>

// Color definitions
#define BLACK   0x0000
#define BLUE    0x001F
#define RED     0xF800
#define GREEN   0x07E0
#define CYAN    0x07FF
#define MAGENTA 0xF81F
#define YELLOW  0xFFE0
#define WHITE   0xFFFF

#define __CS 10
#define __DC 9
TFT_ILI9163C tft = TFT_ILI9163C(__CS, 8, __DC);

#include <OneWire.h> //Librairie du bus OneWire
#include <DallasTemperature.h> //Librairie du capteur
float temp = 25.36; //variable température
OneWire oneWire(2); //Bus One Wire sur la pin 2 de l'arduino
DallasTemperature sensors(&oneWire); //Utilisation du bus Onewire pour les capteurs
DeviceAddress sensorDeviceAddress; //Vérifie la compatibilité des capteurs avec la librairie

//Global.......................................
static unsigned gLastMicro =  0; //Micro Ticker last Time ref
static unsigned gLastMilli  = 0; //Milli Ticker last Time ref
float gLasttemp1  = 0; //reference temperature
float gLasttemp2 = 0;
float temp1 = 0;
float temp2 = 0;
unsigned int gperiod = 100;

void drawNum1()   {
  tft.fillRect(18,14,90,24,YELLOW);
  tft.setCursor(18, 15);
  tft.setTextColor(RED);
  tft.setTextSize(3);
  tft.println(temp1);
  //tft.display(true);
  // Serial.print("temperature: ");
  // Serial.print(temp1); //imprime la température en celsius du capteur 0
  // Serial.println(" C");
}

void drawNum2()   {
  tft.fillRect(18,54,90,24,YELLOW);
  tft.setCursor(18, 55);
  tft.setTextColor(RED);
  tft.setTextSize(3);
  tft.println(temp2);
  //tft.display(true);
  // Serial.print("temperature: ");
  // Serial.print(temp2); //imprime la température en celsius du capteur 0
  // Serial.println(" C");
}

void readTempSensor1()  {
  sensors.requestTemperatures(); //Demande la température aux capteurs
  temp1 = sensors.getTempCByIndex(0);
}

void readTempSensor2()  {
  sensors.requestTemperatures(); //Demande la température aux capteurs
  temp2 = sensors.getTempCByIndex(1);
}

void setup() {
  Serial.begin(9600); //Permet la communication en serial
  sensors.begin(); //Activation des capteurs
  sensors.getAddress(sensorDeviceAddress, 0); //Demande l'adresse du capteur à l'index 0 du bus
  sensors.setResolution(sensorDeviceAddress, 12); //Résolutions possibles: 9,10,11,12
  tft.begin();
  tft.fillScreen(BLUE);
}

void loop(void) {
  // ms Ticker ................................
  unsigned long CurMilli=millis();
  if (CurMilli > gLastMilli + gperiod){
  gLastMilli=CurMilli;
  readTempSensor1();
  readTempSensor2();

  if (temp1 != gLasttemp1)   {
   drawNum1();
   gLasttemp1 = temp1;
  }

if (temp2 != gLasttemp2)   {
   drawNum2();
   gLasttemp2 = temp2;
  }

  } // end of milli ticker

}

******************************************************************************