Help with one wire temperature sensor project

Projects General Guidance
1

Ive been working on a one wire temperature sensor project. I would like to read the temperature of 5 one wire temperature sensors and compare it to a temperature, then set a pin high to light a red green or blue LED.
example:
if (thermistor1 > 78"degrees"){
digitalWrite(Red, HIGH);
}
if (thermistor1 < 78){
digitalWrite(Blue, HIGH);
}
if (thermistor1 == 78){
digitalWrite(Green, HIGH);
}
"Ive tried this way multiple times and returns 'cannot compare pointer to integer' "
I am starting with arduino and do not know alot so any help on this is greatly appreciated!

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

// 1 wire data pin 3
#define ONE_WIRE_BUS 3

OneWire oneWire(ONE_WIRE_BUS);

DallasTemperature sensors(&oneWire);

DeviceAddress Thermistor1 = { 0x28, 0x6A, 0x15, 0x41, 0x05, 0x00, 0x00, 0xE6 };
DeviceAddress Thermistor2 = { 0x28, 0xD0, 0xB1, 0x40, 0x05, 0x00, 0x00, 0x8D };
DeviceAddress Thermistor3 = { 0x28, 0xF2, 0x96, 0x40, 0x05, 0x00, 0x00, 0xFC };
DeviceAddress Thermistor4 = { 0x28, 0x37, 0xB6, 0x40, 0x05, 0x00, 0x00, 0x70 };
DeviceAddress Thermistor5 = { 0x28, 0x8A, 0x1E, 0x41, 0x05, 0x00, 0x00, 0xBF };

int Red = 2;

int Green = 3;

int Blue = 4;

void setup(void)
{
 // Start serial port
 Serial.begin(9600);
 // Start the library
 sensors.begin();
 // Sets the resolution to 12 bit
 sensors.setResolution(Thermistor1, 10);
 sensors.setResolution(Thermistor2, 10);
 sensors.setResolution(Thermistor3, 10);
 sensors.setResolution(Thermistor4, 10);
 sensors.setResolution(Thermistor5, 10);
}

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);
    Serial.print(" F: ");
    Serial.print(DallasTemperature::toFahrenheit(tempC));
  }
 
 pinMode(Red, OUTPUT);
 pinMode(Green, OUTPUT);
 pinMode(Blue, OUTPUT); 
}

void loop(void)
{
 delay(5000);
 Serial.print("Getting temperature...\n\r");
 sensors.requestTemperatures();

 Serial.print("Thermistor 1 temperature is: ");
 printTemperature(Thermistor1);
 Serial.print("\n\r");
 Serial.print("Thermistor 2 temperature is: ");
 printTemperature(Thermistor2);
 Serial.print("\n\r");
 Serial.print("Thermistor 3 temperature is: ");
 printTemperature(Thermistor3);
 Serial.print("\n\r");
 Serial.print("Thermistor 4 temperature is: ");
 printTemperature(Thermistor4);
 Serial.print("\n\r");
 Serial.print("Thermistor 5 temperature is: ");
 printTemperature(Thermistor5);
 Serial.print("\n\r\n\r");

}

sketch_jul21a.ino (1.95 KB)

2

Thermistor1 and thermistor1 are not the same variable. Since the sensors are returning floats you might find it helps to use 78.00 in the if statements. The code you post is verbose and ill-considered, but works OK, so I assume the only problems are with the conditionals.

3

Not that you would care but DS18B20s are not thermisters. They are digital temp sensors.

4

For best results, post the sketch you're trying to compile, not a fragment.

However, Thermistor1 is a device address, not a temperature which accounts for the compiler errors you're getting. Look at this line in the PrintTemperature routine:

  float tempC = sensors.getTempC(deviceAddress);

Which shows how to get the temperature. Once you have it, then you can test it to control your LEDs.

5

thank you wildbill for the help. I know that they are digital temperature sensors and not thermistors, i just named them that for simplicity, but thanks anyway. :slight_smile: