Comparing 3 DS18B20 Temperature sensors.

Projects Programming
1

Hi everybody.
I'm want to compare 3 DS18B20 temp sensors on 1 wire.
How do I do that??
I'm been trying different sketches but I am not getting there.
I want to compare sensor 3 against sensor 1 and get a value, then see if sensor 3 is 5 degrees C higher than sensor 1.
then I want to compare sensor 2 against sensor 1 to see if the temperature is lower than 1 degree.
Does somebody know and could give me a hint how to write this??
Thanks to wildbill I starting to get there, but still having some trouble with the state in the end of sketch.
Status Log

starting one wire sensors
Locating 1-wire devices...
Found 3 devices.
Givarna visar...

Temp solpanel is: C: 28.75

Temp Invatten is: C: 26.00

Temp utvatten is: C: 26.00

Manuellt on = 1, off = 0: 0

Status State1: 0

Status State2: 0

Diff 1 is:2.75

Diff 2 is:0.00

I can't get Diff 2 to change to 1, even moving sensor 2 (utvatten) to same water temp as sensor 3 (solpanel)
Diff 1 works OK
What have I done wrong??

/* This Arduino sketch reads 3 DS18B20 "1-Wire" digital
 temperature sensors. Marcs testing.
*/ 

#include <OneWire.h>
#include <DallasTemperature.h>

// Data wire is plugged into pin 3 on the Arduino
#define ONE_WIRE_BUS 3

// Setup a oneWire instance to communicate with any OneWire devices
OneWire oneWire(ONE_WIRE_BUS);

// Pass our oneWire reference to Dallas Temperature. 
DallasTemperature sensors(&oneWire);

//Adjustments

//Set max pool temp
float  poolMax = 31.0;

//if poolMax paus system
float poolCooldown = 1.0;

//Set solpanel diff to start
float setDiff = 5.0;

//Set minimum diff temp
float minDiff = 1.0;

//set state
int state1 = 0;
int state2 = 0;


// Assign the addresses of your 1-Wire temp sensors.
// Solpanel S3, invatten S1, utvatten S2
DeviceAddress solpanel = { 0x28, 0x43, 0x41, 0xD9, 0x04, 0x00, 0x00, 0x1A };
DeviceAddress invatten = { 0x28, 0x10, 0xBB, 0xD9, 0x04, 0x00, 0x00, 0x76 };
DeviceAddress utvatten = { 0x28, 0x53, 0x70, 0xDA, 0x04, 0x00, 0x00, 0x80 };

// Number of temperature devices found
int numberOfDevices;

//variables used for control logic

float   Temp1, Temp2, Temp3;   //  storage for comparing the inlet and outlet temps
const boolean ON = HIGH;        //  makes the code easier to read
const boolean OFF = LOW;        //  makes the code easier to read

//variables used for control logic
float differential1 = 0.0 ;
float differential2 = 0.0 ;
int invalidCount = 0;

//define pin ManPump On
const int manon = 11;
//define pin for pump relay
const int pumpOn = 13;
const int ledPin = 12;      // the number of the green LED pin
// variables will change:
int manonState = 0;         // variable for reading the Manual On status

//this part of the code runs once to get everything setup and started.

void setup(void)
{
  // start serial port
  Serial.begin(9600);
  // Start up the library
  Serial.println ("starting one wire sensors");
  sensors.begin();
  
  // locate devices on the one wire bus
  Serial.println("");
  Serial.print("Locating 1-wire devices...");
  Serial.println ("");
  Serial.print("Found ");
  Serial.print(sensors.getDeviceCount(), DEC);
  Serial.println(" devices.");
  
  // set the resolution to 10 bit (good enough?)
  sensors.setResolution(solpanel, 10);
  sensors.setResolution(invatten, 10);
  sensors.setResolution(utvatten, 10);
  

    //set pins to output
   { 
  pinMode (pumpOn, OUTPUT);
  pinMode (manon, INPUT);
  pinMode(ledPin, OUTPUT); // green LED
    }
  //give time for everything to start
  delay (2000);
}

void printTemperature(DeviceAddress deviceAddress)
{
  float tempC = sensors.getTempC(deviceAddress);
  if (tempC == -127.00) {
    Serial.print("Error getting temperature");
  } else {
    Serial.print("C: ");
    Serial.print(tempC);
    }
}
void loop(void)
{
// read the state of the switch value:
  manonState = digitalRead(manon);

  // check if the switch is on.
  // if it is, the buttonState is HIGH:
  if (manonState == HIGH) {     
    // turn LED on:    
    digitalWrite(ledPin, HIGH);
    state1 = 1;
  } 
  if (manonState == LOW) {     
    // turn LED off:    
    digitalWrite(ledPin, LOW);
    //state1 = 0;
  } 
    

{ 
  
  Serial.print("Givarna visar...\n\r");
  sensors.requestTemperatures();
  
  Serial.print("Temp solpanel is: ");
  printTemperature(solpanel);
  Serial.print("\n\r");
  Serial.print("Temp Invatten is: ");
  printTemperature(invatten);
  Serial.print("\n\r");
  Serial.print("Temp utvatten is: ");
  printTemperature(utvatten);
  Serial.print("\n\r");
  Serial.println(""); // radbryt
  Serial.print ("Manuellt paa = 1, av = 0: ");
  Serial.println(manonState);
  Serial.println("");
  Serial.print ("Status State1: ");
  Serial.println(state1);
  Serial.println("");
  Serial.print ("Status State2: ");
  Serial.println(state2);
  Serial.println("");
  delay(1500);
 
 
 //Sensors for logic

Temp1 = sensors.getTempC(invatten);
Temp2 = sensors.getTempC(utvatten); 
Temp3 = sensors.getTempC(solpanel);

     
     //difference between solpanel and invatten gives us our differential
      differential1 = Temp3-Temp1;
      Serial.print("Diff 1 is:");
      Serial.println(differential1);
      Serial.println("");
      differential2 = Temp2-Temp1;
      Serial.print("Diff 2 is:");
      Serial.println(differential2);
      Serial.println("");
      
      //logic1
     {
      if ((differential1 > 5.0) && (Temp1 < poolMax)); { // compare the temps,
      (state1 = 1);      // return 1 if heat is on
           
     if (differential1 < 5.0)
    (state1 = 0);
      }
      //Logic2 ( This doesn't work, Why??) 
      {
    if (differential2 > 1.0 );
   (state2 = 1); 
   
    if (differential2 < 1.0 );
    (state2 = 0);
     }
delay (2000);
}

}
}
2

How to use this forum

Please post your sketches.

3

Sounds as if you have solved the tricky part of getting readings from multiple sensors.

To do the comparisons you would save the reading from each sensor into a different variable and then use IF statements to compare them however you want and take the appropriate actions.

4

Mr_Klatjoff:
I'm getting serial temp readings for sensor 1,2,3 but I'm to new to figure this out:
please help.

Sounds like you are almost there. You should be using a subroutine that returns the variable under the same name, like TempC . You need to store them by assigning new names, like ThisC, ThatC and OtherC. You can then get the differences.

diff=ThatC - ThisC etc.

5

Nick_Pyner:

Mr_Klatjoff:
I'm getting serial temp readings for sensor 1,2,3 but I'm to new to figure this out:
please help.

Sounds like you are almost there. You should be using a subroutine that returns the variable under the same name, like TempC . You need to store them by assigning new names, like ThisC, ThatC and OtherC. You can then get the differences.

diff=ThatC - ThisC etc.

I been trying that ! Even tried differential =solpanel-invatten; . This code gave me a number 8 and didn't change holding the sensor 3 .

6

Ah, the poorly named printTemperature function claims another victim.

To get the temp from your sensors, use a construct like this:

Temp1 = sensors.getTempC(invatten);
7

Mr_Klatjoff:
I been trying that !

Try something like this. Parts from a larger programme but has the essentials.

#include <OneWire.h>
#include <DallasTemperature.h>
#include <SPI.h>                  
#include <Ethernet.h>            // Ethernet 
#include <HttpClient.h>          // Cosm lib
#include <Cosm.h>                // Cosm lib
#include <PCD8544.h>             // Nokia 5110
#include <SD.h>                  // SD card
#include <string.h>              // from Date As Filename 
#include "RTClib.h"              // from Date As Filename
#include "Wire.h"                // LCD disp, SD card, and serial

#define DS1307_ADDRESS 0x68

RTC_DS1307 RTC;
static PCD8544 lcd;


byte InThermo[8] =  {0x28, 0x39, 0xFD, 0x50, 0x04, 0x00, 0x00, 0x69};
byte OutThermo[8] = {0x28, 0x09, 0xA9, 0xC0, 0x03, 0x00, 0x00, 0x95};
byte DrainThermo[8] = {0x28, 0x62, 0xA5, 0x2D, 0x04, 0x00, 0x00, 0x21};

#define ONE_WIRE_BUS 3
OneWire oneWire(ONE_WIRE_BUS);
DallasTemperature sensors(&oneWire);


int  second, minute, hour, weekDay, monthDay, month, year;

int k=0;                                                                                                
float InTemp, OutTemp, DrainTemp;    




void setup() {
  Wire.begin();
  Serial.begin(9600);

  delay(300);//Wait for newly restarted system to stabilize
  lcd.setCursor (0,0);

  delay(500);
  lcd.setCursor (0,1);

  pinMode(10, OUTPUT);

  

lcd.clear();

  Serial.println("LABEL,Time,InTemp,OutTemp,diff,DrainTemp");

  sensors.setResolution(InThermo, 12);
  sensors.setResolution(OutThermo, 12);
  sensors.setResolution(DrainThermo, 12);

  Serial.println("Starting multiple datastream upload to Cosm...");
  Serial.println();

  while (Ethernet.begin(mac) != 1)
  {
    Serial.println("Error getting IP address via DHCP, trying again...");
    delay(10000);
  }
}

void loop() {

 Serial.print("DATA,TIME,       "); 
  int ret=0;
  //get the values from the DS8B20's 
  sensors.requestTemperatures();

  float InTemp = (sensorValue(InThermo));
  float OutTemp = (sensorValue(OutThermo));  
  float DrainTemp = (sensorValue(DrainThermo)); 

  float diff = OutTemp - InTemp;


  Serial.print(InTemp);
  Serial.print(" ,  ");
  Serial.print(OutTemp);
  Serial.print(" ,  ");
  Serial.print(DrainTemp);
  Serial.println(" ,  ");

  lcd.setCursor(49,0);
  lcd.print(InTemp);
  lcd.setCursor(49,1);
  lcd.print (OutTemp);
  lcd.setCursor(49,2);
  lcd.print(DrainTemp);

  k=k+1;  

 
  delay(850);
}  // loop ends here

//sensorValue function
float sensorValue (byte deviceAddress[])
{
  float tempC = sensors.getTempC (deviceAddress);
  return tempC;
}

byte bcdToDec(byte val)  {
  // Convert binary coded decimal to normal decimal numbers
  return ( (val/16*10) + (val%16) );
}
8

wildbill:
Ah, the poorly named printTemperature function claims another victim.

To get the temp from your sensors, use a construct like this:

Temp1 = sensors.getTempC(invatten);

Thanks wildbill, that was a code I didn't try :roll_eyes:
Is it possible to get the reading in a value of 1.x , now it's only showing me 1 degree C diff?

9

Mr_Klatjoff:
is it possible to get the reading in a value of 1.x , now it's only showing me 1 degree C diff?

Declare differential as float instead of int.

10

wildbill:

Mr_Klatjoff:
is it possible to get the reading in a value of 1.x , now it's only showing me 1 degree C diff?

Declare differential as float instead of int.

Thanks wildbill, U are a rock! :wink:
but now I'm having a new trouble.
What am I doing wrong in the end of the new sketch I updated?
Can't get state2 to change, what am I doing wrong??
state1 works.

11 
      //Logic2 ( This doesn't work, Why??) 
      {
    if (differential2 > 1.0 ); // get rid of semicolon
   (state2 = 1); 
   
    if (differential2 < 1.0 ); // and this one
    (state2 = 0);
     }

Those semicolons should not be there - compare the similar code you have above.

12

wildbill:

      //Logic2 ( This doesn't work, Why??)

{
    if (differential2 > 1.0 ); // get rid of semicolon
   (state2 = 1);
   
    if (differential2 < 1.0 ); // and this one
    (state2 = 0);
     }




Those semicolons should not be there - compare the similar code you have above.

Thanks wildbill!
Now it works, I'll come back to you when I mess it up again :wink: