TEMP Temperature Sensor Module Quickstart Guide

The Temperature Sensor Module provides a conveniently packaged DS18B20 1-wire temperature sensor that can be daisy-chained to connect multiple sensors on a single cable.

Module Pinout

The module provides two identical sets of headers on opposite sides. For basic use only one set is required: the headers are directly linked inside the module, and the second set is provided for your convenience to make it easy to daisy-chain multiple modules together.

GND: Connect to GND (0V) on your microcontroller.

DATA: Connect to a digital I/O pin on your microcontroller.

VIN: Connect to 5V on your microcontroller, for 5V microcontrollers such a Freetronics Eleven, EtherTen, EtherMega, Arduino Uno, etc. Connect to 3.3V for 3.3V microcontrollers. The module is capable of operating from 3.3V to 5.5V.

Basic Connections

Connect GND on the module to GND on your Arduino; VIN on the module to the power pin on your Arduino; and DATA on the module to one of the digital I/O pins. In this example we've used D2.

Reading Values

The example below reads a value from a single connected Temperature Sensor Module once per second, and reports the value via the serial console. Open the Arduino IDE, create a new sketch, and paste in the following code:

#define REF_PIN 2
void getCurrentTemp( int *sign, int *whole, int *fract);
char temp_string[10];

void setup(){
  Serial.begin(9600);
  // initialize DS18B20 datapin
  digitalWrite(REF_PIN, LOW);
  pinMode(REF_PIN, INPUT);      // sets the digital pin as input (logic 1)
  pinMode(15, INPUT);
}

void loop(){
  getCurrentTemp(temp_string);
  Serial.println(temp_string);
  delay(1000);
}

void OneWireReset (int Pin) // reset.  Should improve to act as a presence pulse
{
  digitalWrite (Pin, LOW);
  pinMode (Pin, OUTPUT);        // bring low for 500 us
  delayMicroseconds (500);
  pinMode (Pin, INPUT);
  delayMicroseconds (500);
}

void OneWireOutByte (int Pin, byte d) // output byte d (least sig bit first).
{
  byte n;

  for (n=8; n!=0; n--)
  {
    if ((d & 0x01) == 1)  // test least sig bit
    {
      digitalWrite (Pin, LOW);
      pinMode (Pin, OUTPUT);
      delayMicroseconds (5);
      pinMode (Pin, INPUT);
      delayMicroseconds (60);
    }
    else
    {
      digitalWrite (Pin, LOW);
      pinMode (Pin, OUTPUT);
      delayMicroseconds (60);
      pinMode (Pin, INPUT);
    }

    d = d>>1; // now the next bit is in the least sig bit position.
  }
}


byte OneWireInByte (int Pin) // read byte, least sig byte first
{
  byte d, n, b;

  for (n=0; n<8; n++)
  {
    digitalWrite (Pin, LOW);
    pinMode (Pin, OUTPUT);
    delayMicroseconds (5);
    pinMode (Pin, INPUT);
    delayMicroseconds (5);
    b = digitalRead (Pin);
    delayMicroseconds (50);
    d = (d >> 1) | (b<<7); // shift d to right and insert b in most sig bit position
  }
  return (d);
}


void getCurrentTemp (char *temp)
{
  int HighByte, LowByte, TReading, Tc_100, sign, whole, fract;

  OneWireReset (REF_PIN);
  OneWireOutByte (REF_PIN, 0xcc);
  OneWireOutByte (REF_PIN, 0x44); // perform temperature conversion, strong pullup for one sec

  OneWireReset (REF_PIN);
  OneWireOutByte (REF_PIN, 0xcc);
  OneWireOutByte (REF_PIN, 0xbe);

  LowByte = OneWireInByte (REF_PIN);
  HighByte = OneWireInByte (REF_PIN);
  TReading = (HighByte << 8) + LowByte;
  sign = TReading & 0x8000;  // test most sig bit
  if (sign) // negative
  {
    TReading = (TReading ^ 0xffff) + 1; // 2's comp
  }
  Tc_100 = (6 * TReading) + TReading / 4;    // multiply by (100 * 0.0625) or 6.25

  whole = Tc_100 / 100;  // separate off the whole and fractional portions
  fract = Tc_100 % 100;

  if (sign) {
    temp[0] = '-';
  } else {
    temp[0] = '+';
  }

  if (whole/100 == 0) {
    temp[1] = ' ';
  } else {
    temp[1] = whole/100+'0';
  }

  temp[2] = (whole-(whole/100)*100)/10 +'0' ;
  temp[3] = whole-(whole/10)*10 +'0';
  temp[4] = '.';
  temp[5] = fract/10 +'0';
  temp[6] = fract-(fract/10)*10 +'0';
  temp[7] = '\0';
}

Upload the sketch to your microcontroller, open the serial console, make sure it's set to 9600bps to match the setting in the sketch, and watch the values reported from the temperature sensor. Try holding it with your fingers for a few seconds to see the readings increase as it warms up.