Temperature Sensor not giving proper values

Question

In my current project I am reading temperature through sensor which is having only two wires.

To read sensor values, I have used below schematic which I have found on Arduino Project Hub site.

In my project I am using below Arduino program.

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

// Data wire is plugged into pin 2 on the Arduino
#define ONE_WIRE_BUS 2

// 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);

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

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


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

  Serial.print("Temperature is: ");
  Serial.print(sensors.getTempCByIndex(0)); // Why "byIndex"? 
    // You can have more than one IC on the same bus. 
    // 0 refers to the first IC on the wire
    delay(1000);
}

After doing all this I am getting this output on serial monitor.

At which step I am doing wrong?

score 1 · Answer 1 · answered Jan 02 '21 at 21:25

The -127 for your temperature reading is actually the error code for DEVICE_DISCONNECTED_C.

In the library's example code, they put an if that checks for this error code before printing the temperature:

if(tempC != DEVICE_DISCONNECTED_C) 
{
  Serial.print("Temperature for the device 1 (index 0) is: ");
  Serial.println(tempC);
}

Since your sensor has only 2 wires, according to Wikipedia, you need a capacitor to power the sensor:

One distinctive feature of the bus is the possibility of using only two wires — data and ground. To accomplish this, 1-Wire devices include an 800 pF capacitor to store charge and power the device during periods when the data line is active.

This should hopefully resolve your issues.

Temperature Sensor not giving proper values

1 Answers1