How to Use DS18B20 Temperature Sensor: Examples, Pinouts, and Specs

The DS18B20 is a digital temperature sensor that provides temperature readings in degrees Celsius with an accuracy of ±0.5°C. It communicates with microcontrollers and other digital devices using the 1-Wire protocol, which allows multiple sensors to be connected to a single data wire. This sensor is widely used in a variety of applications, including environmental monitoring, home automation, and industrial control systems.

• Supply Voltage: 3.0V to 5.5V
• Operating Temperature Range: -55°C to +125°C
• Accuracy: ±0.5°C from -10°C to +85°C
• Resolution: Selectable from 9 to 12 bits
• Unique 64-bit Serial Code: Allows for multiple sensors on the same 1-Wire bus
• Conversion Time: 750ms at 12-bit resolution

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 a digital input/output pin on your microcontroller.
4. Place a 4.7kΩ pull-up resistor between the DQ pin and the VDD pin.

• Ensure that the power supply voltage is within the specified range to avoid damaging the sensor.
• Use the 4.7kΩ pull-up resistor on the DQ line for reliable communication.
• Avoid running the sensor wires close to high-voltage or high-current lines to minimize interference.
• For long cable runs, consider using a lower value pull-up resistor and shielded cable.

#include <OneWire.h>
#include <DallasTemperature.h>

// Data wire is connected to 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)
{ 
  // Request temperature measurements from the sensor
  sensors.requestTemperatures(); 
  // Fetch and print the temperature in Celsius
  Serial.print("Temperature is: ");
  Serial.print(sensors.getTempCByIndex(0)); 
  Serial.println("°C");
  
  // Wait 1 second before requesting new data
  delay(1000);
}

• No Temperature Readings: Ensure the pull-up resistor is correctly placed and the sensor is properly powered.
• Inaccurate Readings: Check for proper grounding and stable power supply. Ensure the sensor is not exposed to rapid temperature changes.
• Multiple Sensors Not Working: Verify each sensor has a unique address and that the 1-Wire bus is correctly configured.

• Double-check wiring, especially the pull-up resistor on the DQ line.
• Use the sensors.getAddress() function to ensure each sensor has a unique address.
• For issues with multiple sensors, use the sensors.search() function to find all devices on the bus.

Q: Can I use the DS18B20 sensor without an external power supply?

A: Yes, the DS18B20 supports "parasite power" mode, where it draws power from the data line. This requires only two wires: the data line and ground.

Q: How many DS18B20 sensors can I connect to a single microcontroller pin?

A: You can connect many sensors to a single pin, limited by the bus capacitance and the quality of your pull-up resistor. In practice, around 10-20 sensors are often manageable.

Q: How do I waterproof the DS18B20 sensor for outdoor use?

A: You can purchase the DS18B20 in a waterproof probe form, or you can waterproof a standard sensor using appropriate sealing techniques and materials like heat shrink tubing and silicone sealant.