DS18B20 Arduino: Complete Waterproof Temperature Sensor Guide

When a project requires measuring temperature in wet environments, harsh conditions, or at distance from the main controller, the DS18B20 Arduino combination becomes my go-to solution. After designing temperature monitoring systems for everything from aquariums to industrial brewing equipment, I’ve come to appreciate why this sensor dominates the waterproof temperature sensing market.

The DS18B20 stands apart from other temperature sensors for several compelling reasons. It communicates digitally over a single data wire, maintains accuracy even with long cable runs, and each sensor carries a unique 64-bit address allowing multiple sensors on one bus. The waterproof probe version wraps all this capability in a stainless steel housing that handles submersion without complaint.

This tutorial covers everything you need to successfully implement DS18B20 Arduino projects, from understanding the underlying technology to wiring multiple sensors and troubleshooting common problems.

Understanding DS18B20 Sensor Technology

The DS18B20, manufactured by Maxim Integrated (formerly Dallas Semiconductor), uses the proprietary 1-Wire protocol for communication. This protocol deserves attention because it fundamentally shapes how you design DS18B20 Arduino circuits.

How 1-Wire Communication Works

Unlike I2C or SPI which require dedicated clock lines, the 1-Wire protocol transmits data and timing information over a single wire. The Arduino acts as the bus master, initiating all communication sequences with reset pulses and time-slot-based data transfer.

Each communication begins with the master pulling the data line low for at least 480 microseconds (the reset pulse), then releasing it. Connected DS18B20 sensors respond with presence pulses, signaling they’re ready for commands. Data bits are then exchanged through precisely timed voltage transitions.

The protocol’s elegance enables several practical advantages:

Advantage	Practical Benefit
Single data wire	Minimizes wiring complexity
Unique 64-bit addresses	Multiple sensors on one pin
No signal degradation	Works reliably over long distances
Parasite power mode	Operation with only two wires
Built-in CRC checking	Data integrity verification

Temperature Measurement Mechanism

Inside the DS18B20, a bandgap-based temperature sensor converts thermal energy to a digital value. The sensor counts clock cycles from a temperature-dependent oscillator and compares them to a stable reference oscillator. This differential counting technique provides consistent accuracy across the operating temperature range.

The measurement resolution is user-configurable from 9 to 12 bits, with corresponding conversion times from 93.75ms to 750ms. Higher resolution takes longer but provides finer temperature granularity.

Resolution	Increment	Conversion Time
9-bit	0.5°C	93.75 ms
10-bit	0.25°C	187.5 ms
11-bit	0.125°C	375 ms
12-bit	0.0625°C	750 ms

The default 12-bit resolution suits most applications, providing excellent accuracy with sub-second response times.

DS18B20 Technical Specifications

Understanding specifications helps determine if the DS18B20 fits your project requirements and operating environment.

Parameter	Specification
Operating Voltage	3.0V to 5.5V
Temperature Range	-55°C to +125°C
Accuracy	±0.5°C (from -10°C to +85°C)
Resolution	9 to 12 bits (programmable)
Conversion Time	93.75ms to 750ms
Standby Current	750nA typical
Active Current	1mA typical, 1.5mA max
Communication	1-Wire protocol
Data Line	Open-drain, requires pull-up
Unique Address	64-bit ROM code

The waterproof probe version adds a stainless steel housing with PVC-jacketed cable. While the DS18B20 chip handles temperatures up to 125°C, the PVC jacket typically limits practical use to around 100°C for continuous operation. For higher temperatures, look for probes with silicone or Teflon insulation.

DS18B20 Pinout and Form Factors

The DS18B20 comes in several packages, with the TO-92 transistor-style package and waterproof probe being most common for Arduino projects.

TO-92 Package Pinout

With the flat side of the TO-92 package facing you (text readable):

Pin	Name	Function
1 (Left)	GND	Ground
2 (Center)	DQ	Data In/Out
3 (Right)	VDD	Power Supply

Waterproof Probe Wire Colors

Waterproof probes use color-coded wires, though colors vary between manufacturers. The most common scheme:

Wire Color	Connection
Red	VDD (Power)
Yellow or White	DQ (Data)
Black	GND (Ground)

Always verify wire functions with your specific probe’s documentation or use a multimeter to identify ground (typically has continuity to the metal housing).

Wiring DS18B20 to Arduino

Proper wiring is critical for reliable DS18B20 Arduino operation. The most important element is the pull-up resistor on the data line.

Components Required

Component	Quantity	Notes
Arduino Uno/Nano/Mega	1	Any Arduino board works
DS18B20 Sensor or Probe	1+	Waterproof probe recommended
4.7kΩ Resistor	1	Pull-up for data line
Breadboard	1	For prototyping
Jumper Wires	3+	Appropriate lengths

Standard Wiring (Normal Power Mode)

Normal power mode provides the most reliable operation and is recommended for most applications:

DS18B20 Pin	Arduino Connection
VDD (Red)	5V
DQ (Yellow)	Digital Pin 2 + 4.7kΩ to 5V
GND (Black)	GND

The 4.7kΩ pull-up resistor connects between the data line and 5V, maintaining a stable high state when the bus is idle. This resistor is essential; the Arduino’s internal pull-ups are too weak (20-50kΩ) for reliable 1-Wire communication.

Parasite Power Mode Wiring

In parasite power mode, the sensor draws power through the data line, requiring only two wires:

DS18B20 Pin	Arduino Connection
VDD	GND (tie to ground)
DQ	Digital Pin 2 + 4.7kΩ to 5V
GND	GND

Parasite mode reduces wiring but can cause issues during temperature conversion when current demand spikes. For multi-sensor setups or long cable runs, normal power mode is more reliable.

Installing Required Arduino Libraries

The DS18B20 Arduino interface requires two libraries that handle the complex 1-Wire protocol timing.

OneWire Library Installation

Step 1: Open Arduino IDE and navigate to Sketch → Include Library → Manage Libraries

Step 2: Search for “OneWire” in the Library Manager

Step 3: Find “OneWire by Paul Stoffregen” and click Install

This library handles low-level 1-Wire communication, managing the precise timing requirements that would be tedious to implement manually.

DallasTemperature Library Installation

Step 1: With Library Manager still open, search for “DallasTemperature”

Step 2: Find “DallasTemperature by Miles Burton” and click Install

This library builds on OneWire, providing convenient functions specifically for DS18B20 and similar temperature sensors.

DS18B20 Arduino Code Examples

With hardware connected and libraries installed, you can start reading temperature values.

Basic Single Sensor Reading

This sketch reads temperature from one DS18B20 and displays it on the Serial Monitor:

#include <OneWire.h>

#include <DallasTemperature.h>

#define ONE_WIRE_BUS 2  // Data wire connected to pin 2

OneWire oneWire(ONE_WIRE_BUS);

DallasTemperature sensors(&oneWire);

void setup() {

  Serial.begin(9600);

  Serial.println(“DS18B20 Temperature Sensor”);

  sensors.begin();

}

void loop() {

  sensors.requestTemperatures();  // Send command to get temperatures

  float tempC = sensors.getTempCByIndex(0);

  float tempF = tempC * 9.0 / 5.0 + 32.0;

  if (tempC == DEVICE_DISCONNECTED_C) {

    Serial.println(“Error: Could not read temperature”);

    return;

  }

  Serial.print(“Temperature: “);

  Serial.print(tempC);

  Serial.print(“°C | “);

  Serial.print(tempF);

  Serial.println(“°F”);

  delay(1000);

}

The getTempCByIndex(0) function retrieves temperature from the first (index 0) sensor found on the bus. The DEVICE_DISCONNECTED_C constant (-127°C) indicates communication failure.

Finding DS18B20 Sensor Addresses

When using multiple sensors, you need each sensor’s unique 64-bit address. This utility sketch discovers and prints all connected sensor addresses:

#include <OneWire.h>

#include <DallasTemperature.h>

#define ONE_WIRE_BUS 2

OneWire oneWire(ONE_WIRE_BUS);

DallasTemperature sensors(&oneWire);

void setup() {

  Serial.begin(9600);

  sensors.begin();

  Serial.print(“Found “);

  Serial.print(sensors.getDeviceCount());

  Serial.println(” sensors.”);

  DeviceAddress tempAddress;

  for (int i = 0; i < sensors.getDeviceCount(); i++) {

    if (sensors.getAddress(tempAddress, i)) {

      Serial.print(“Sensor “);

      Serial.print(i);

      Serial.print(” Address: “);

      printAddress(tempAddress);

      Serial.println();

    }

  }

}

void loop() {

  // Nothing needed here

}

void printAddress(DeviceAddress deviceAddress) {

  for (uint8_t i = 0; i < 8; i++) {

    if (deviceAddress[i] < 16) Serial.print(“0”);

    Serial.print(deviceAddress[i], HEX);

  }

}

Record the printed addresses for use in multi-sensor projects where you need to identify specific sensors.

Reading Multiple DS18B20 Sensors

With multiple sensors on the same bus, you can read by index or by address. Reading by address ensures you always know which physical sensor provides each reading:

#include <OneWire.h>

#include <DallasTemperature.h>

#define ONE_WIRE_BUS 2

OneWire oneWire(ONE_WIRE_BUS);

DallasTemperature sensors(&oneWire);

// Define sensor addresses (replace with your actual addresses)

DeviceAddress sensor1 = {0x28, 0xFF, 0x64, 0x1E, 0x2A, 0x17, 0x04, 0x9B};

DeviceAddress sensor2 = {0x28, 0xFF, 0x53, 0x2A, 0x2A, 0x17, 0x04, 0xD7};

void setup() {

  Serial.begin(9600);

  sensors.begin();

  // Set resolution for faster readings if needed

  sensors.setResolution(sensor1, 10);

  sensors.setResolution(sensor2, 10);

}

void loop() {

  sensors.requestTemperatures();

  float temp1 = sensors.getTempC(sensor1);

  float temp2 = sensors.getTempC(sensor2);

  Serial.print(“Sensor 1: “);

  Serial.print(temp1);

  Serial.print(“°C | Sensor 2: “);

  Serial.print(temp2);

  Serial.println(“°C”);

  delay(1000);

}

Troubleshooting DS18B20 Arduino Problems

After troubleshooting countless DS18B20 installations, I’ve compiled the most common issues and their solutions.

Problem: Reading Shows -127°C

This value indicates the sensor didn’t respond or communication failed.

Cause	Solution
Missing pull-up resistor	Add 4.7kΩ between data and 5V
Wrong pin number in code	Verify pin definition matches wiring
Loose connections	Check all wire connections
Defective sensor	Try a different DS18B20
Wrong wire identification	Verify probe wire colors with documentation

Problem: Reading Shows 85°C

The DS18B20 powers up with 85°C in its temperature register. Reading this value means the sensor hasn’t completed a conversion.

Cause	Solution
Reading too quickly after power-on	Add delay after sensors.begin()
Insufficient conversion time	Wait for conversion to complete
Parasite power issues	Switch to normal power mode

Problem: Intermittent Readings or Errors

Sporadic failures often indicate marginal signal integrity.

Cause	Solution
Long cable runs	Use lower pull-up value (3.3kΩ) or add capacitor
Multiple sensors overloading bus	Reduce pull-up to 2.7kΩ-3.3kΩ
Electrical noise	Add 100nF capacitor between VDD and GND
Poor connections	Use soldered connections instead of breadboard

Problem: Multiple Sensors Not All Detected

When some sensors on a shared bus aren’t recognized:

Cause	Solution
Pull-up resistor too high	Lower to 3.3kΩ or 2.7kΩ for many sensors
Bus capacitance too high	Limit cable length or use multiple buses
Address conflicts (rare)	Verify all sensors have unique addresses

For installations with more than 5-6 sensors, reducing the pull-up resistor value often resolves detection issues. Some users report success with 14+ sensors using a 2.7kΩ pull-up.

DS18B20 vs Other Temperature Sensors

Choosing the right sensor depends on your specific requirements.

Feature	DS18B20	DHT11	LM35	Thermocouple
Interface	1-Wire	Single-wire	Analog	Analog (amplified)
Temp Range	-55 to +125°C	0 to 50°C	-55 to +150°C	-200 to +1350°C
Accuracy	±0.5°C	±2°C	±0.5°C	±1-2°C
Waterproof	Yes (probe version)	No	No	Yes
Multi-sensor	One pin for many	One pin each	One analog pin each	One pin each
Humidity	No	Yes	No	No
Price	~$2-5	~$1-2	~$1	~$5-15

The DS18B20 excels for underwater measurements, multi-point temperature monitoring, and applications requiring accuracy over a wide range. For combined temperature and humidity, the DHT22 is better suited. For extreme temperatures, thermocouples remain necessary.

Practical DS18B20 Arduino Applications

The DS18B20 Arduino combination suits numerous real-world projects.

Aquarium Temperature Monitoring

The waterproof probe handles permanent submersion, monitoring tank temperature with enough accuracy to detect problematic fluctuations before they stress fish.

Brewing and Fermentation Control

Monitor mash temperatures, fermentation vessel conditions, and cooling water simultaneously with multiple sensors on a single data bus. The probe’s stainless steel construction handles wet brewing environments.

HVAC System Monitoring

Track supply and return air temperatures, duct conditions, and room temperatures across a building using long cable runs that maintain signal integrity.

Soil Temperature Measurement

Monitor ground temperature for agriculture, gardening, or geothermal studies. The waterproof housing survives burial in moist soil.

Industrial Process Control

Track temperatures at multiple points along a production line, triggering alarms or controls when values exceed thresholds.

Useful Resources and Downloads

Official Documentation and Libraries

Resource	Location
DS18B20 Datasheet	analog.com/media/en/technical-documentation/data-sheets/ds18b20.pdf
OneWire Library	github.com/PaulStoffregen/OneWire
DallasTemperature Library	github.com/milesburton/Arduino-Temperature-Control-Library
Arduino Library Manager	Built into Arduino IDE

Additional Learning Resources

Resource	Description
Maxim 1-Wire Application Notes	Detailed protocol documentation
Random Nerd Tutorials	Comprehensive DS18B20 guides
Arduino Forum	Community troubleshooting support

Hardware Suppliers

Common sources for DS18B20 sensors include Amazon, AliExpress, Adafruit, SparkFun, and Mouser. When purchasing waterproof probes, check reviews for quality issues, as cheap clones sometimes have sealing problems.

Frequently Asked Questions About DS18B20 Arduino

How many DS18B20 sensors can I connect to one Arduino pin?

Theoretically unlimited, since each sensor has a unique address. Practically, 10-20 sensors work reliably with appropriate pull-up resistor adjustment. Beyond 5-6 sensors, reduce the pull-up from 4.7kΩ to 2.7kΩ-3.3kΩ. Very long cable runs or many sensors may require multiple buses on different Arduino pins.

Can I use DS18B20 with ESP8266 or ESP32?

Absolutely. The same OneWire and DallasTemperature libraries work with ESP8266 and ESP32 boards. Use 3.3V power and appropriate GPIO pins. Some users prefer adding a level shifter when using 5V sensors with 3.3V microcontrollers, though direct connection often works.

Why does my waterproof probe fail at high temperatures?

The DS18B20 chip handles 125°C, but the PVC cable jacket softens around 80-100°C. For sustained high-temperature use, purchase probes with silicone or Teflon insulation, or use the TO-92 package with appropriate heat-resistant wiring.

What’s the maximum cable length for DS18B20?

Reliable operation up to 100 meters is achievable with proper wiring: use twisted pair or shielded cable, ensure solid connections, and adjust the pull-up resistor for your specific cable capacitance. Shorter runs (under 10m) rarely cause issues.

How do I improve DS18B20 response time?

Reduce the resolution from 12-bit to 9-bit or 10-bit, which decreases conversion time from 750ms to under 200ms. Use sensors.setResolution(address, 9) to configure. For truly fast response, thermistors or RTDs provide quicker thermal response than the DS18B20’s internal sensor.

Final Thoughts on DS18B20 Arduino Projects

The DS18B20 Arduino combination delivers reliable digital temperature sensing that scales from single-sensor prototypes to multi-point monitoring installations. Its 1-Wire protocol eliminates wiring complexity while maintaining signal integrity over distances that would defeat analog sensors.

The waterproof probe version opens applications that other sensors simply cannot address: permanent underwater monitoring, outdoor weather stations, buried soil sensors, and industrial processes involving moisture or liquids. At a few dollars per sensor, there’s little reason to compromise with less capable alternatives.

Start with a single sensor to understand the wiring and library usage, then expand to multi-sensor configurations as your projects demand. The unique addressing system makes scaling straightforward, with each new sensor requiring only a connection to the shared bus. That simplicity, combined with proven reliability, explains why the DS18B20 remains the dominant choice for Arduino temperature sensing projects requiring waterproof capability or multi-point measurement.