ds18x20 2 temperature sensors

Projects Programming
1

Hi,
I have two sensors (same type) and I want to compare the temperatures ,in order to activate 2 different motors ,depending on which temperature is higher.

If "temperature 1 " is higher than "temperature 2" I want to start "motor 1" .If "temperature 2 " is higher than "temperature 1" I want to start "motor 2"

The sensors are working on the same bus ,and so far I've managed to check the temperatures with this scetch,but I don't know how to compare the temperature values in digital sensors

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

// Data wire is plugged into port 2 on the Arduino
#define ONE_WIRE_BUS 2
#define TEMPERATURE_PRECISION 9

// Setup a oneWire instance to communicate with any OneWire devices (not just Maxim/Dallas temperature ICs)
OneWire oneWire(ONE_WIRE_BUS);

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

// arrays to hold device addresses
DeviceAddress insideThermometer, outsideThermometer;

void setup(void)
{
// start serial port
Serial.begin(9600);
Serial.println("Dallas Temperature IC Control Library Demo");

// Start up the library
sensors.begin();

// locate devices on the bus
Serial.print("Locating devices...");
Serial.print("Found ");
Serial.print(sensors.getDeviceCount(), DEC);
Serial.println(" devices.");

// report parasite power requirements
Serial.print("Parasite power is: ");
if (sensors.isParasitePowerMode()) Serial.println("ON");
else Serial.println("OFF");

// assign address manually. the addresses below will beed to be changed
// to valid device addresses on your bus. device address can be retrieved
// by using either oneWire.search(deviceAddress) or individually via
// sensors.getAddress(deviceAddress, index)
//insideThermometer = { 0x28, 0x1D, 0x39, 0x31, 0x2, 0x0, 0x0, 0xF0 };
//outsideThermometer = { 0x28, 0x3F, 0x1C, 0x31, 0x2, 0x0, 0x0, 0x2 };

// search for devices on the bus and assign based on an index. ideally,
// you would do this to initially discover addresses on the bus and then
// use those addresses and manually assign them (see above) once you know
// the devices on your bus (and assuming they don't change).
//
// method 1: by index
if (!sensors.getAddress(insideThermometer, 0)) Serial.println("Unable to find address for Device 0");
if (!sensors.getAddress(outsideThermometer, 1)) Serial.println("Unable to find address for Device 1");

// method 2: search()
// search() looks for the next device. Returns 1 if a new address has been
// returned. A zero might mean that the bus is shorted, there are no devices,
// or you have already retrieved all of them. It might be a good idea to
// check the CRC to make sure you didn't get garbage. The order is
// deterministic. You will always get the same devices in the same order
//
// Must be called before search()
//oneWire.reset_search();
// assigns the first address found to insideThermometer
//if (!oneWire.search(insideThermometer)) Serial.println("Unable to find address for insideThermometer");
// assigns the seconds address found to outsideThermometer
//if (!oneWire.search(outsideThermometer)) Serial.println("Unable to find address for outsideThermometer");

// show the addresses we found on the bus
Serial.print("Device 0 Address: ");
printAddress(insideThermometer);
Serial.println();

Serial.print("Device 1 Address: ");
printAddress(outsideThermometer);
Serial.println();

// set the resolution to 9 bit
sensors.setResolution(insideThermometer, TEMPERATURE_PRECISION);
sensors.setResolution(outsideThermometer, TEMPERATURE_PRECISION);

Serial.print("Device 0 Resolution: ");
Serial.print(sensors.getResolution(insideThermometer), DEC);
Serial.println();

Serial.print("Device 1 Resolution: ");
Serial.print(sensors.getResolution(outsideThermometer), DEC);
Serial.println();
}

// function to print a device address
void printAddress(DeviceAddress deviceAddress)
{
for (uint8_t i = 0; i < 8; i++)
{
// zero pad the address if necessary
if (deviceAddress < 16) Serial.print("0");
_ Serial.print(deviceAddress*, HEX);_
_ }_
_}_
_// function to print the temperature for a device*_
void printTemperature(DeviceAddress deviceAddress)
{
* float tempC = sensors.getTempC(deviceAddress);*
* Serial.print("Temp C: ");*
* Serial.print(tempC);*
* Serial.print(" Temp F: ");*
* Serial.print(DallasTemperature::toFahrenheit(tempC));*
}
// function to print a device's resolution
void printResolution(DeviceAddress deviceAddress)
{
* Serial.print("Resolution: ");*
* Serial.print(sensors.getResolution(deviceAddress));*
* Serial.println(); *
}
// main function to print information about a device
void printData(DeviceAddress deviceAddress)
{
* Serial.print("Device Address: ");*
* printAddress(deviceAddress);*
* Serial.print(" ");*
* printTemperature(deviceAddress);*
* Serial.println();*
}
void loop(void)
{
* // call sensors.requestTemperatures() to issue a global temperature*
* // request to all devices on the bus*
* Serial.print("Requesting temperatures...");*
* sensors.requestTemperatures();*
* Serial.println("DONE");*
* // print the device information*
* printData(insideThermometer);*
* printData(outsideThermometer);*
}
Thanx in advance!

2

before we start helping you, post you code correctly, IN CODE TAGS

look at this example

//This is using code tags
thisVariable[i] = looksCorrect;

//This is not using code tags
thisVariable = looksIncorrect; //and is now italic and missing [ i ]
You will notice your code is partly italic
So, please post you code inbetween [ code ] and [ /code ] without the spaces

3 
#include <OneWire.h>
#include <DallasTemperature.h>

// Data wire is plugged into port 2 on the Arduino
#define ONE_WIRE_BUS 2
#define TEMPERATURE_PRECISION 9

// Setup a oneWire instance to communicate with any OneWire devices (not just Maxim/Dallas temperature ICs)
OneWire oneWire(ONE_WIRE_BUS);

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

// arrays to hold device addresses
DeviceAddress insideThermometer, outsideThermometer;

void setup(void)
{
  // start serial port
  Serial.begin(9600);
  Serial.println("Dallas Temperature IC Control Library Demo");

  // Start up the library
  sensors.begin();

  // locate devices on the bus
  Serial.print("Locating devices...");
  Serial.print("Found ");
  Serial.print(sensors.getDeviceCount(), DEC);
  Serial.println(" devices.");

  // report parasite power requirements
  Serial.print("Parasite power is: "); 
  if (sensors.isParasitePowerMode()) Serial.println("ON");
  else Serial.println("OFF");

  // assign address manually.  the addresses below will beed to be changed
  // to valid device addresses on your bus.  device address can be retrieved
  // by using either oneWire.search(deviceAddress) or individually via
  // sensors.getAddress(deviceAddress, index)
  //insideThermometer = { 0x28, 0x1D, 0x39, 0x31, 0x2, 0x0, 0x0, 0xF0 };
  //outsideThermometer   = { 0x28, 0x3F, 0x1C, 0x31, 0x2, 0x0, 0x0, 0x2 };

  // search for devices on the bus and assign based on an index.  ideally,
  // you would do this to initially discover addresses on the bus and then 
  // use those addresses and manually assign them (see above) once you know 
  // the devices on your bus (and assuming they don't change).
  // 
  // method 1: by index
  if (!sensors.getAddress(insideThermometer, 0)) Serial.println("Unable to find address for Device 0"); 
  if (!sensors.getAddress(outsideThermometer, 1)) Serial.println("Unable to find address for Device 1"); 

  // method 2: search()
  // search() looks for the next device. Returns 1 if a new address has been
  // returned. A zero might mean that the bus is shorted, there are no devices, 
  // or you have already retrieved all of them.  It might be a good idea to 
  // check the CRC to make sure you didn't get garbage.  The order is 
  // deterministic. You will always get the same devices in the same order
  //
  // Must be called before search()
  //oneWire.reset_search();
  // assigns the first address found to insideThermometer
  //if (!oneWire.search(insideThermometer)) Serial.println("Unable to find address for insideThermometer");
  // assigns the seconds address found to outsideThermometer
  //if (!oneWire.search(outsideThermometer)) Serial.println("Unable to find address for outsideThermometer");

  // show the addresses we found on the bus
  Serial.print("Device 0 Address: ");
  printAddress(insideThermometer);
  Serial.println();

  Serial.print("Device 1 Address: ");
  printAddress(outsideThermometer);
  Serial.println();

  // set the resolution to 9 bit
  sensors.setResolution(insideThermometer, TEMPERATURE_PRECISION);
  sensors.setResolution(outsideThermometer, TEMPERATURE_PRECISION);

  Serial.print("Device 0 Resolution: ");
  Serial.print(sensors.getResolution(insideThermometer), DEC); 
  Serial.println();

  Serial.print("Device 1 Resolution: ");
  Serial.print(sensors.getResolution(outsideThermometer), DEC); 
  Serial.println();
}

// function to print a device address
void printAddress(DeviceAddress deviceAddress)
{
  for (uint8_t i = 0; i < 8; i++)
  {
    // zero pad the address if necessary
    if (deviceAddress[i] < 16) Serial.print("0");
    Serial.print(deviceAddress[i], HEX);
  }
}

// function to print the temperature for a device
void printTemperature(DeviceAddress deviceAddress)
{
  float tempC = sensors.getTempC(deviceAddress);
  Serial.print("Temp C: ");
  Serial.print(tempC);
  Serial.print(" Temp F: ");
  Serial.print(DallasTemperature::toFahrenheit(tempC));
}

// function to print a device's resolution
void printResolution(DeviceAddress deviceAddress)
{
  Serial.print("Resolution: ");
  Serial.print(sensors.getResolution(deviceAddress));
  Serial.println();    
}

// main function to print information about a device
void printData(DeviceAddress deviceAddress)
{
  Serial.print("Device Address: ");
  printAddress(deviceAddress);
  Serial.print(" ");
  printTemperature(deviceAddress);
  Serial.println();
}

void loop(void)
{ 
  // call sensors.requestTemperatures() to issue a global temperature 
  // request to all devices on the bus
  Serial.print("Requesting temperatures...");
  sensors.requestTemperatures();
  Serial.println("DONE");

  // print the device information
  printData(insideThermometer);
  printData(outsideThermometer);
}

Hoping that's the right way.Sorry but I am a new at this!!! :slight_smile:

4

This is the sample code that is included in <DallasTemperature.h> library ("multiple").
I know that I have to set the outputs for the motor relays and I know how to do that.My only problem is how to make the comparison between sensors (in celcious degrees for example).

5

I fear that this project of yours may be too complicated for you and would heavily recommend learning the language, because comparing 2 values is one of the more basic aspects of any programming language.

But here you go:

//This compares if the first device's temperature is less than  the second device's temperature
if(sensors.getTempC(deviceAddress1) < sensors.getTempC(deviceAddress2)){
  //do something
}
6

It wasn;t working with this code (error while compiling) ,but I've managed to fix it.Here is the code that I used .It works fine.Thanx for your help!

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

// Data wire is plugged into port 2 on the Arduino
#define ONE_WIRE_BUS 2
#define TEMPERATURE_PRECISION 9

#define motor1 11
#define motor2 12

// Setup a oneWire instance to communicate with any OneWire devices (not just Maxim/Dallas temperature ICs)
OneWire oneWire(ONE_WIRE_BUS);

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

// arrays to hold device addresses
DeviceAddress insideThermometer, outsideThermometer;

void setup(void)
{ pinMode (motor1 ,OUTPUT);
pinMode (motor2 ,OUTPUT);
  // start serial port
  Serial.begin(9600);
  Serial.println("Dallas Temperature IC Control Library Demo");

  // Start up the library
  sensors.begin();

  // locate devices on the bus
  Serial.print("Locating devices...");
  Serial.print("Found ");
  Serial.print(sensors.getDeviceCount(), DEC);
  Serial.println(" devices.");

  // report parasite power requirements
  Serial.print("Parasite power is: "); 
  if (sensors.isParasitePowerMode()) Serial.println("ON");
  else Serial.println("OFF");

  // assign address manually.  the addresses below will beed to be changed
  // to valid device addresses on your bus.  device address can be retrieved
  // by using either oneWire.search(deviceAddress) or individually via
  // sensors.getAddress(deviceAddress, index)
  //insideThermometer = { 0x28, 0x1D, 0x39, 0x31, 0x2, 0x0, 0x0, 0xF0 };
  //outsideThermometer   = { 0x28, 0x3F, 0x1C, 0x31, 0x2, 0x0, 0x0, 0x2 };

  // search for devices on the bus and assign based on an index.  ideally,
  // you would do this to initially discover addresses on the bus and then 
  // use those addresses and manually assign them (see above) once you know 
  // the devices on your bus (and assuming they don't change).
  // 
  // method 1: by index
  if (!sensors.getAddress(insideThermometer, 0)) Serial.println("Unable to find address for Device 0"); 
  if (!sensors.getAddress(outsideThermometer, 1)) Serial.println("Unable to find address for Device 1"); 

  // method 2: search()
  // search() looks for the next device. Returns 1 if a new address has been
  // returned. A zero might mean that the bus is shorted, there are no devices, 
  // or you have already retrieved all of them.  It might be a good idea to 
  // check the CRC to make sure you didn't get garbage.  The order is 
  // deterministic. You will always get the same devices in the same order
  //
  // Must be called before search()
  //oneWire.reset_search();
  // assigns the first address found to insideThermometer
  //if (!oneWire.search(insideThermometer)) Serial.println("Unable to find address for insideThermometer");
  // assigns the seconds address found to outsideThermometer
  //if (!oneWire.search(outsideThermometer)) Serial.println("Unable to find address for outsideThermometer");

  // show the addresses we found on the bus
  Serial.print("Device 0 Address: ");
  printAddress(insideThermometer);
  Serial.println();

  Serial.print("Device 1 Address: ");
  printAddress(outsideThermometer);
  Serial.println();

  // set the resolution to 9 bit
  sensors.setResolution(insideThermometer, TEMPERATURE_PRECISION);
  sensors.setResolution(outsideThermometer, TEMPERATURE_PRECISION);

  Serial.print("Device 0 Resolution: ");
  Serial.print(sensors.getResolution(insideThermometer), DEC); 
  Serial.println();

  Serial.print("Device 1 Resolution: ");
  Serial.print(sensors.getResolution(outsideThermometer), DEC); 
  Serial.println();
}

// function to print a device address
void printAddress(DeviceAddress deviceAddress)
{
  for (uint8_t i = 0; i < 8; i++)
  {
    // zero pad the address if necessary
    if (deviceAddress[i] < 16) Serial.print("0");
    Serial.print(deviceAddress[i], HEX);
  }
}

// function to print the temperature for a device
void printTemperature(DeviceAddress deviceAddress)
{
  float tempC = sensors.getTempC(deviceAddress);
  Serial.print("Temp C: ");
  Serial.print(tempC);
  Serial.print(" Temp F: ");
  Serial.print(DallasTemperature::toFahrenheit(tempC));
}

// function to print a device's resolution
void printResolution(DeviceAddress deviceAddress)
{
  Serial.print("Resolution: ");
  Serial.print(sensors.getResolution(deviceAddress));
  Serial.println();    
}

// main function to print information about a device
void printData(DeviceAddress deviceAddress)
{
  Serial.print("Device Address: ");
  printAddress(deviceAddress);
  Serial.print(" ");
  printTemperature(deviceAddress);
  Serial.println();
}

void loop(void)
{ 
  // call sensors.requestTemperatures() to issue a global temperature 
  // request to all devices on the bus
  Serial.print("Requesting temperatures...");
  sensors.requestTemperatures();
  Serial.println("DONE");

  // print the device information
  printData(insideThermometer);
  printData(outsideThermometer);
  
  
  if(sensors.getTempC(insideThermometer) < sensors.getTempC(outsideThermometer))
  {
    delay (10000);
 digitalWrite (motor2 ,HIGH);
  }
  else {  digitalWrite (motor2 ,LOW); }
  
  if(sensors.getTempC(insideThermometer) > sensors.getTempC(outsideThermometer))
  {
    delay (10000);
 digitalWrite (motor1 ,HIGH);
  }
  else
{ digitalWrite (motor1 ,LOW);
}
}