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GPIO Project 9 - LCD Temperature
Beginner
30 Minuten
114,90
In this project, you will learn how to use aDS18B20 temperature sensor to measure the ambient temperature and display this value on a16x2 LCD display with I2C interface. This is a great application to present data visually.
Connection diagram
Connection of the DS18B20 temperature sensor:
- Zwart draad: Connect with GND (pin 6).
- Rood wire: Connection with 3.3V (pin 1).
- Geel draad:
- Connect with GPIO 4 (pin 7).
- Plaats a 10kΩ weerstand tussen de gele draad en 3.3V ( pin 1).
Connect het LCD display:
- VCC: Connection with 5V (pin 2).
- GND: Connect with GND (pin 6).
- SDA: Connect with GPIO 2 (pin 3).
- SCL: Connection with GPIO 3 (pin 5).
Pinout Reference
GPIO | Pin # | Function | Connection |
| GPIO 4 | Pin 7 | Temperature sensor data | DS18B20-yellow wire |
| GPIO 2 | Pin 3 | I2C SDA | LCD SDA |
| GPIO 3 | Pin 5 | I2C SCL | LCD SCL |
| 3.3V | Pin 1 | Nutrition | DS18B20-red wire |
| 5V | Pin 2 | Nutrition | LCD VCC |
| GND | Pin 6 | Earth (Ground) | DS18B20 and LCD |
Preparation
Step 1: Install required libraries
Run the following commands in the terminal to install the libraries for the DS18B20 and LCD:
sudo apt-get update
sudo apt-get install python3-pip
pip3 install RPLCDActivate the 1-Wire interface for the DS18B20:
- Open the configuration menu:
sudo raspi-config- Go to Interface Options > 1-Wire and turn it on.
- Reboot the Raspberry Pi.
Check if the DS18B20 is recognized:
ls /sys/bus/w1/devices/You would see an address like 28-XXXXXXXXXXXX.
Python-code in Thonny
Step 1: Write your code
Open the Thonny Python IDE and enter the following code:
import os
import glob
from time import sleep
from RPLCD.i2c import CharLCD
# DS18B20-instellingen
base_dir = '/sys/bus/w1/devices/'
device_folder = glob.glob(base_dir + '28*')[0]
device_file = device_folder + '/w1_slave'
# LCD-instellingen
lcd = CharLCD(i2c_expander='PCF8574', address=0x27, cols=16, rows=2)
def read_temp_raw():
"""Lees ruwe data van de DS18B20."""
with open(device_file, 'r') as f:
lines = f.readlines()
return lines
def read_temp():
"""Verwerk de data en retourneer de temperatuur in graden Celsius."""
lines = read_temp_raw()
while lines[0].strip()[-3:] != 'YES':
sleep(0.2)
lines = read_temp_raw()
equals_pos = lines[1].find('t=')
if equals_pos != -1:
temp_string = lines[1][equals_pos + 2:]
temp_c = float(temp_string) / 1000.0
return temp_c
try:
while True:
temp = read_temp()
print(f"Temperatuur: {temp:.1f} °C")
# Toon de temperatuur op het LCD
lcd.clear()
lcd.write_string("Temp: {:.1f} C".format(temp))
sleep(2)
except KeyboardInterrupt:
print("\nProgramma gestopt.")
lcd.clear()
Step 2: Save the file
Click File > Save As and name the file lcd_temperature.py.
Step 3: Run the script
Click the greenRun button (▶) at the top the Thonny interface.
How does it work?
- DS18B20 Temperature Sensor:
- Reads the temperature via 1-Wire protocol and returns the value in degrees Celsius.
- LCD Display:
- Displays the temperature value on a 16x2 LCD display.
- Repeat:
- The program reads and displays the temperature every 2 seconds.
Result
- The ambient temperature is continuously read by the DS18B20 and displayed on the LCD screen.
- The temperature is also displayed in the terminal.
Experimenting
- Add Fahrenheit:
- Add code to display Fahrenheit as well:
python
Copy code
- Add code to display Fahrenheit as well:
- Add LED:
- Turn on an LED when the temperature exceeds a threshold.
- Logging:
- Log the temperature to a file for further analysis:
with open("temp_log.txt", "a") as log:
log.write(f"{temp:.1f} °C\n")
