In many Raspberry Pi projects, monitoring temperature is critical, especially for IoT and environmental applications. Using a digital sensor like the DS18B20, you can measure temperature accurately and efficiently. This project will walk you through how to set up and read data from a digital temperature sensor using Python on a Raspberry Pi.
Purpose of the Project
The purpose of this project is to teach you how to measure temperature using a digital sensor like DS18B20 on a Raspberry Pi. This knowledge is useful for various applications, including environmental monitoring, home automation, and data logging.
Data Types and Variable Table for Measuring Temperature Using a Digital Sensor
| Variable Name | Data Type | Description |
| temp_raw | String | Holds the raw data read from the temperature sensor |
| temperature_celsius | Float | Stores the final temperature in Celsius |
Syntax Table for Measuring Temperature Using a Digital Sensor
| Topic | Syntax | Simple Example |
| Reading Sensor Data | os.system(‘modprobe w1-gpio’) | os.system(‘modprobe w1-gpio’) |
| Reading Raw Data | open(‘/sys/bus/w1/devices/<device>/w1_slave’) | open(‘/sys/bus/w1/devices/28-000005e2fdc3/w1_slave’) |
| Temperature Calculation | temperature = float(temp_str) / 1000.0 | temperature = float(temp_str) / 1000.0 |
Required Components
- Raspberry Pi (any model with GPIO support)
- DS18B20 digital temperature sensor
- 4.7kΩ resistor (pull-up resistor)
- Jumper wires
Circuit Diagram
The following diagram illustrates the circuit setup for the DS18B20 temperature sensor:
(Insert a circuit diagram showing the Raspberry Pi GPIO pins connected to the DS18B20 sensor)
Circuit Connection Table for Measuring Temperature Using a Digital Sensor
| Component | Raspberry Pi Pin | DS18B20 Pin |
| VCC (+3.3V) | Pin 1 (3.3V) | Pin 1 (VDD) |
| Data (GPIO) | Pin 7 (GPIO 4) | Pin 2 (Data) |
| Ground | Pin 6 (Ground) | Pin 3 (Ground) |
| Pull-up Resistor (4.7kΩ) | Between Pin 1 and GPIO 4 | — |
Warning
- Make sure that the DS18B20 sensor is wired correctly to avoid damaging the sensor or Raspberry Pi.
- Use a 4.7kΩ pull-up resistor between the VCC and Data pin to ensure stable readings.
Circuit Analysis for Measuring Temperature Using a Digital Sensor
In this circuit, the DS18B20 temperature sensor communicates with the Raspberry Pi using the 1-Wire protocol, which allows multiple devices to communicate through a single data pin. The pull-up resistor ensures signal integrity during communication between the Raspberry Pi and the sensor.
Installing Libraries
To get the DS18B20 working, you need to enable the 1-Wire interface on the Raspberry Pi and install necessary Python libraries:
sudo modprobe w1-gpio
sudo modprobe w1-therm
Writing the Code Using Python
import os
import glob
import time
# Load 1-wire drivers
os.system(‘modprobe w1-gpio’)
os.system(‘modprobe w1-therm’)
# Get the device folder for the sensor
base_dir = ‘/sys/bus/w1/devices/’
device_folder = glob.glob(base_dir + ’28*’)[0]
device_file = device_folder + ‘/w1_slave’
# Function to read raw data from the sensor
def read_temp_raw():
with open(device_file, ‘r’) as f:
return f.readlines()
# Function to process the raw data and extract temperature
def read_temp():
lines = read_temp_raw()
while lines[0].strip()[-3:] != ‘YES’:
time.sleep(0.2)
lines = read_temp_raw()
temp_output = lines[1].find(‘t=’)
if temp_output != -1:
temp_str = lines[1][temp_output+2:]
temperature_celsius = float(temp_str) / 1000.0
return temperature_celsius
try:
while True:
temp_c = read_temp()
print(f”Temperature: {temp_c:.2f}°C”)
time.sleep(1)
except KeyboardInterrupt:
print(“Program stopped”)
Explanation of the Code
- Loading 1-Wire Drivers: The modprobe command loads the necessary drivers to communicate with the DS18B20 sensor using the 1-Wire protocol.
- Device Folder: The code identifies the sensor’s unique address under the sys/bus/w1/devices/ folder.
- Reading Raw Data: The read_temp_raw() function retrieves raw sensor data.
- Temperature Conversion: The raw data is processed to calculate the temperature in Celsius, dividing the sensor’s output by 1000 to get the final value.
Running the Code and Checking the Output
- Save the code as temp_sensor.py.
Run the code using the command:
python3 temp_sensor.py
- The temperature in Celsius will be printed every second on your terminal.
Expanding the Project
- Add the ability to log the temperature data into a file for historical tracking.
- Display the temperature reading on an LCD or create a web interface to monitor the data remotely.
- Implement alerts for high or low temperatures using email notifications or a buzzer.
Common Problems and Solutions
- Problem: No temperature reading or an error message.
- Solution: Ensure that the 1-Wire interface is enabled on the Raspberry Pi, and double-check the wiring and the presence of the pull-up resistor.
- Problem: Inconsistent or fluctuating temperature values.
- Solution: Make sure the pull-up resistor is connected correctly, and try to place the sensor in a more stable environment.
FAQ
Q1: What is the purpose of the pull-up resistor?
A1: The pull-up resistor ensures that the communication line between the Raspberry Pi and the DS18B20 sensor remains stable, allowing accurate data transmission.
Q2: Can I use multiple DS18B20 sensors with one Raspberry Pi?
A2: Yes, the 1-Wire protocol allows you to connect multiple sensors to the same data pin, and each sensor will have a unique address.
Conclusion
By following this guide, you’ve successfully learned how to measure temperature using a digital sensor like the DS18B20 on a Raspberry Pi. This simple yet powerful technique allows you to build projects that rely on temperature monitoring, such as environmental sensing, home automation, and IoT applications.