DS18b20

Description
This module measures the temperature and reports it through the 1-wire bus to the Arduino.  It uses the extremely popular DS18b20 digital thermometer.

KY001

Specs

The DS18B20 digital thermometer provides 9-bit to 12-bit Celsius temperature measurements and has an alarm function with nonvolatile user-programmable upper and lower trigger points. The DS18B20 communicates over a 1-Wire® bus that by definition requires only one data line (and ground) for communication with a central microprocessor. It has an operating temperature range of -55°C to +125°C and is accurate to ±0.5°C over the range of -10°C to +85°C. In addition, the DS18B20 can derive power directly from the data line (“parasite power”), eliminating the need for an external power supply.

Each DS18B20 has a unique 64-bit serial code, which allows multiple DS18B20s to function on the same 1-Wire bus.

Parts Required

You will require the following

Arduino UNO (or equivalent)
KY-001 Temperature sensor module
USB cable

Connections

Pin – = connect to GND
Pin (middle) = connect to +5V
Pin S = Signal, connect to Arduino Digital port 10

Code

Arduino Example

[codesyntax lang=”cpp”]

#include <OneWire.h>
 
// DS18S20 Temperature chip i/o
OneWire ds(10);  // on pin 10
 
void setup(void) {
  // initialize inputs/outputs
  // start serial port
  Serial.begin(9600);
}
 
void loop(void) {
 
  //For conversion of raw data to C
  int HighByte, LowByte, TReading, SignBit, Tc_100, Whole, Fract;
 
  byte i;
  byte present = 0;
  byte data[12];
  byte addr[8];
 
  if ( !ds.search(addr)) {
      Serial.print("No more addresses.\n");
      ds.reset_search();
      return;
  }
 
  Serial.print("R=");
  for( i = 0; i < 8; i++) {
    Serial.print(addr[i], HEX);
    Serial.print(" ");
  }
 
  if ( OneWire::crc8( addr, 7) != addr[7]) {
      Serial.print("CRC is not valid!\n");
      return;
  }
 
  if ( addr[0] == 0x10) {
      Serial.print("Device is a DS18S20 family device.\n");
  }
  else if ( addr[0] == 0x28) {
      Serial.print("Device is a DS18B20 family device.\n");
  }
  else {
      Serial.print("Device family is not recognized: 0x");
      Serial.println(addr[0],HEX);
      return;
  }
 
  ds.reset();
  ds.select(addr);
  ds.write(0x44,1);         // start conversion, with parasite power on at the end
 
  delay(1000);     // maybe 750ms is enough, maybe not
  // we might do a ds.depower() here, but the reset will take care of it.
 
  present = ds.reset();
  ds.select(addr);    
  ds.write(0xBE);         // Read Scratchpad
 
  Serial.print("P=");
  Serial.print(present,HEX);
  Serial.print(" ");
  for ( i = 0; i < 9; i++) {           // we need 9 bytes
    data[i] = ds.read();
    Serial.print(data[i], HEX);
    Serial.print(" ");
  }
  Serial.print(" CRC=");
  Serial.print( OneWire::crc8( data, 8), HEX);
  Serial.println();
 
  //Conversion of raw data to C
  LowByte = data[0];
  HighByte = data[1];
  TReading = (HighByte << 8) + LowByte;
  SignBit = TReading & 0x8000;  // test most sig bit
  if (SignBit) // 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 (SignBit) // If its negative
  {
     Serial.print("-");
  }
  Serial.print(Whole);
  Serial.print(".");
  if (Fract < 10)
  {
     Serial.print("0");
  }
  Serial.print(Fract);
 
  Serial.print("\n");
  //End conversion to C
}

[/codesyntax]