One Wire Digital Temperature Sensor – DS18B20+

One Wire Digital Temperature Sensor – DS18B20+

This is the latest DS18B20 1-Wire digital temperature sensor from Maxim IC. Reports degrees C with 9 to 12-bit precision, -55C to 125C (+/-0.5C). Each sensor has a unique 64-Bit Serial number etched into it – allows for a huge number of sensors to be used on one data bus.

This is a wonderful part that is the cornerstone of many data-logging and temperature control projects.

Features:

• Unique 1-Wire interface requires only one port pin for communication
• Each device has a unique 64-bit serial code stored in an onboard ROM
• Multidrop capability simplifies distributed temperature sensing applications
• Requires no external components
• Can be powered from the data line. The power supply range is 3.0V to 5.5V
• Measures temperatures from -55°C to +125°C (-67°F to +257°F)
• ±0.5°C accuracy from -10°C to +85°C
• Thermometer resolution is user-selectable from 9 to 12 bits
• Converts temperature to 12-bit digital word in 750ms (max.)
• User-definable nonvolatile (NV) alarm settings
• Alarm search command identifies and addresses devices whose temperature is outside of programmed limits (temperature alarm condition)
• Applications include thermostatic controls, industrial systems, consumer products, thermometers, or any thermally sensitive system

Specifications:

• Supply voltage: 3.0 to 5.5 V
• Standby current: 1 μA
• Active current: 1.5 mA
• Measuring range: -55 °C to + 125 °C (-67 °F to +257 °F)
• Accuracy (Thermometer Error):
  • ±0.5 °C from -10 °C to +85 °C
  • ±1 °C from -30 °C to +100 °C
  • ±2 °C from -55 °C to +125 °C
• Resolution: 9-bit to 12-bit (programmable)
• Conversion time: < 750 ms (12-bit resolution)
• Communication protocol: 1-Wire® bus protocol
• Package: 3-pin TO-92

DS18B20+ (TO-220) Device Pin Out:

DS18B20+ Block Diagram:

Connecting DS18B20+ to Arduino:

You’ll need to download the Arduino Librarys “OneWire” and “DallasTemp” which you can find below, and install them to your Arduino Libraries folder.

Connect your Arduino as per this diagram:

Notes:

• You don’t need a Scottish Uno, and Uno will do!
• You only need one 4.7K resistor per circuit, no matter how many temperature sensors you add in a daisy chain formation

Example Arduino Code for DS18B20+:

/* Example code for the DS18B20+ One-Wire Digital Temperature Sensor */
// Include Arduino libraries:
#include <OneWire.h>
#include <DallasTemperature.h>
// Define the Arduino data pin connected to the 1-Wire bus:
#define ONE_WIRE_BUS 2
// Create a new instance of the oneWire class to communicate with any OneWire device:
OneWire oneWire(ONE_WIRE_BUS);
// Pass the oneWire reference to DallasTemperature library:
DallasTemperature sensors(&oneWire);
void setup() {
  // Begin serial communication at a baud rate of 9600:
	Serial.begin(9600);
  // Start up the library:
	sensors.begin();
}
void loop() {
  // Send the command for all devices on the bus to perform a temperature conversion:
	sensors.requestTemperatures();
  // Fetch the temperature in degrees Celsius for device index:
  	float tempC = sensors.getTempCByIndex(0); // the index 0 refers to the first device
  	float tempF = sensors.getTempFByIndex(0); // Fetch the temperature in degrees Fahrenheit for device index
	Serial.print("Temperature: "); //Output to the serial monitor
	Serial.print(tempC);   // Print the temperature in Celsius
	Serial.print(" \xC2\xB0");
	Serial.print("C  |  ");
	Serial.print(tempF);	// Print the temperature in Fahrenheit
	Serial.print(" \xC2\xB0");
	Serial.println("F");
  // Wait 1 second:
	delay(1000);
}

Documents:

• DS18B20 Datasheet
• OneWire (Arduino Library)
• DallasTemp (Arduino Library)
• DS18B20 PCB (Eagle PCB Data File)
• TO-92 Step File (Mechanical Model)