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Arduino Mega 2560 Project 6: DS18B20 Temperature Sensor

Posted by Fiona Su on

Introduction:
DS18B20 Temperature Sensor is a digital temperature sensor from DALLAS U.S. It can be used to quantify environmental temperature testing.
The temperature range is -55 ~ +125 ℃, inherent temperature resolution 0.5 ℃. It also support multi-point mesh networking. Three DS18B20 can be deployed on three lines to achieve multi-point temperature measurement. It has a 9-12 bit serial output.
Specification:
  • Supply Voltage: 3.3V to 5V
  • Temperature range: -55 °C ~ +125 °C
  • Interface: Digital
  • Size: 30*20mm
  • Weight: 3g

Connection Diagram:

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Sample Code:
http://www.pjrc.com/teensy/arduino_libraries/OneWire.zip

#include <OneWire.h>
 int DS18S20_Pin = 2; //DS18S20 Signal pin on digital 2
 //Temperature chip i/o
OneWire ds(DS18S20_Pin);  // on digital pin 2
 void setup(void) {
  Serial.begin(9600);
}
 void loop(void) {
  float temperature = getTemp();
  Serial.println(temperature);
   
  delay(100); //just here to slow down the output so it is easier to read
   
}
 
float getTemp(){
  //returns the temperature from one DS18S20 in DEG Celsius
 
  byte data[12];
  byte addr[8];
 
  if ( !ds.search(addr)) {
      //no more sensors on chain, reset search
      ds.reset_search();
      return -1000;
  }
 
  if ( OneWire::crc8( addr, 7) != addr[7]) {
      Serial.println("CRC is not valid!");
      return -1000;
  }
 
  if ( addr[0] != 0x10 && addr[0] != 0x28) {
      Serial.print("Device is not recognized");
      return -1000;
  }
 
  ds.reset();
  ds.select(addr);
  ds.write(0x44,1); // start conversion, with parasite power on at the end
 
  byte present = ds.reset();
  ds.select(addr);    
  ds.write(0xBE); // Read Scratchpad
 
   
  for (int i = 0; i < 9; i++) { // we need 9 bytes
    data[i] = ds.read();
  }
  ds.reset_search();
   
  byte MSB = data[1];
  byte LSB = data[0];
 
  float tempRead = ((MSB << 8) | LSB); //using two's compliment
  float TemperatureSum = tempRead / 16;
   
  return TemperatureSum;   
}

Project List

Buy it here>>Sensor Starter Kit For Arduino Mega 2560

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