How to Use DS18B20 1-Wire Temperature Sensor Probe Cable: Examples, Pinouts, and Specs

The DS18B20 is a digital temperature sensor that provides 9-bit to 12-bit Celsius temperature measurements. The sensor 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 alarm function with nonvolatile user-programmable upper and lower trigger points. The DS18B20 is widely used in a variety of applications, including HVAC environmental controls, temperature monitoring systems inside buildings, equipment, or machinery, and process monitoring and control systems.

• Home automation systems
• Aquarium temperature monitoring
• Industrial temperature control
• Weather stations
• Food and beverage temperature monitoring

• Power Supply Range: 3.0V to 5.5V
• Operating Temperature Range: -55°C to +125°C
• Accuracy: ±0.5°C from -10°C to +85°C
• Programmable Resolution: 9-bit to 12-bit
• Unique 64-bit Serial Code Stored in On-Board ROM
• Multi-drop Capability Simplifies Distributed Temperature Sensing Applications

1. Connect the GND pin to the ground of the power supply.
2. Connect the VDD pin to a 3.0V to 5.5V power supply.
3. Connect the DQ pin to the data input on your microcontroller.
4. Optionally, connect a 4.7kΩ pull-up resistor between the DQ pin and the VDD pin for proper communication on the 1-Wire bus.

• Use a pull-up resistor of 4.7kΩ on the DQ line when connecting to a microcontroller.
• Avoid long wire lengths to minimize the resistance and capacitance on the data line, which can cause communication issues.
• Ensure that the power supply is stable and within the specified voltage range.

#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
OneWire oneWire(ONE_WIRE_BUS);

// Pass our oneWire reference to Dallas Temperature sensor 
DallasTemperature sensors(&oneWire);

void setup(void)
{
  // Start serial communication for debugging
  Serial.begin(9600);
  // Start up the library
  sensors.begin();
}

void loop(void)
{ 
  // Call sensors.requestTemperatures() to issue a global temperature 
  // request to all devices on the bus
  sensors.requestTemperatures(); 

  // Fetch the temperature in degrees Celsius for device index 0
  float tempC = sensors.getTempCByIndex(0);
  
  // Check if reading was successful
  if(tempC != DEVICE_DISCONNECTED_C) 
  {
    Serial.print("Temperature: ");
    Serial.print(tempC);
    Serial.println("°C");
  } 
  else
  {
    Serial.println("Error: Could not read temperature data");
  }

  delay(1000);
}

• Temperature Readings Are Inaccurate: Ensure that the DS18B20 is not placed near heat-generating components and that the correct pull-up resistor is used.
• No Data on the Bus: Check the connections and the pull-up resistor on the DQ line. Ensure that the microcontroller's data pin is correctly configured.
• Fluctuating Readings: Stabilize the power supply and avoid long wires that can introduce noise.

Q: Can I connect multiple DS18B20 sensors to the same data line?

A: Yes, the DS18B20 supports multi-drop capability, allowing multiple sensors to be connected on the same 1-Wire bus.

Q: How do I set the resolution of the temperature measurements?

A: The resolution can be set programmatically using the DallasTemperature library functions. Refer to the library documentation for specific instructions.

Q: What is the purpose of the unique 64-bit serial code?

A: The unique serial code allows for the identification of each sensor on a shared 1-Wire bus, which is essential for addressing specific sensors in a multi-sensor setup.

Q: How long can the cable be between the sensor and the microcontroller?

A: The maximum cable length depends on the quality of the cable and the pull-up resistor value. For longer cables, a lower value resistor may be needed to maintain signal integrity. Keep the cable as short as practical to ensure reliable communication.