DS18B20 Temperature Sensor Detailed Explanation and Use Cases

DS18B20 Temperature Sensor Overview

The DS18B20 is a digital temperature sensor from Maxim Integrated that provides high accuracy, a simple interface, and unique device identification, making it a top choice in embedded and IoT applications.

Key Features

1-Wire Communication Protocol

The DS18B20 uses 1-Wire protocol, which allows data transmission and even power over a single wire, plus ground.

 Basic Operation Flow

1. Reset pulse by the master.

2. Presence pulse from the DS18B20.

3. Master sends a ROM command (e.g., Match ROM, Skip ROM).

4. Master sends a function command (e.g., Convert T, Read Scratchpad).

5. Sensor responds with temperature or status data.

 ROM Commands

• Read ROM: Read device's unique 64-bit ID.

• Match ROM: Select a specific sensor on the bus.

• Skip ROM: Broadcast to all sensors.

• Search ROM: Identify all sensors on the bus.

Internal Memory (Scratchpad)

The DS18B20 has a 9-byte scratchpad memory, structured as:

The configuration register allows you to set the resolution:

Temperature Reading Formula

After reading the temperature bytes:

Powering Modes

1. Normal Mode

• VDD connected to 3.0–5.5V.

• DQ (data) connected with a 4.7kΩ pull-up resistor.

2. Parasitic Mode

• Only DQ and GND are used.

• Sensor steals power during the high state of the data line.

• Requires careful timing during conversions.

Typical Circuit

Advantages

• Minimal wiring (1-Wire).

• Easily network multiple sensors on one bus.

• Accurate and stable digital output.

• Waterproof versions for harsh environments.

• Programmable resolution and alarms.

Common Use Cases

Scientific and Industrial

• Lab temperature monitoring

• Industrial machinery thermal monitoring

• Process control systems

Home Automation

• Smart thermostats

• Room-based climate control

• Floor heating systems

Agriculture and Environment

• Greenhouse temperature control

• Soil temperature monitoring

• Weather stations

Liquid Immersion and Waterproof Applications

• Aquarium temperature sensing

• Water tank monitoring

• Food storage and cold chain logistics

Data Logging

• Long-term temperature data collection

• Solar panel performance tracking

• Refrigeration monitoring systems

Development Platforms

Supported on most microcontroller platforms:

• Arduino: Uses libraries like OneWire and DallasTemperature.

• STM32: Uses custom 1-Wire or HAL/GPIO-based implementations.

• Raspberry Pi: Accessible via GPIO with Python (e.g., using w1thermsensor).

• ESP32: Great for IoT applications; supports DS18B20 over Wi-Fi.