KY-001 Temperature sensor (DS18B20)

// Required libraries will be imported
#include <OneWire.h>
#include <DallasTemperature.h>            

// Here the input pin is declared to which the sensor module is connected
#define KY001_Signal_PIN 4

// Libraries are configured
OneWire oneWire(KY001_Signal_PIN);          
DallasTemperature sensors(&oneWire);    


void setup() {

    // Initialize serial output
    Serial.begin(9600);
    Serial.println("KY-001 temperature measurement");

    // Sensor is initialized
    sensors.begin();  
}

//main program loop
void loop()
{
    // Temperature measurement is started...
    sensors.requestTemperatures();
    // ... and output measured temperature
    Serial.print("Temperature: ");
    Serial.print(sensors.getTempCByIndex(0));
    Serial.println(" °C");

    delay(1000); // 1s pause until next measurement
}

The DS18B20 digital thermometer provides 9-bit to 12-bit Celsius temperature measurements and has an alarm function with non-volatile, user-programmable high and low trigger points.

This means that the sensor has a programmable upper and lower limit. The DS18B20 communicates via a 1-wire bus, which requires only one data line for communication with a central microprocessor. In addition, the DS18B20 can draw power directly from the data line ("parasite power"). This eliminates the need for an external power source. Each DS18B20 has a unique 64-bit serial code. This allows multiple sensors to operate on the same 1-Wire bus and be evaluated by only one microprocessor.

Applications that can benefit from this feature include HVAC environmental controls, temperature monitoring systems in buildings, plants or machinery, and process monitoring and control systems.

Technical data

Chipset	DS18B20
Communication Protocol	1-Wire
Accuracy	9 to 12 Bit
Measuring range	-55 °C to +125 °C
Measurement accuracy	±0.5 °C from -10 °C to +85 °C

Pin assignment

Code example Raspberry Pi

Pin assignment Raspberry Pi:

Raspberry Pi	Sensor
GPIO4 [Pin 7]	Signal
3.3 V [Pin 1]	+V
GND [Pin 6]	GND

One-Wire Configuration Raspberry Pi

In order for the Raspberry Pi to communicate with the One-Wire bus, it must first be activated. For this, the file "/boot/config.txt" must be edited. Therefore open the file with the following command:

sudo nano /boot/config.txt

Add the following content to the end of the file:

dtoverlay=w1-gpio,gpiopin=4

Afterwards you can save the file with the key combination [CTRL+O]. Confirm this with [Enter] and exit the editor with [CTRL+X]. Now restart your Raspberry Pi with the following command:

sudo reboot

Now you can apply the following example. Here a console output is generated as soon as a signal is detected.

# coding=utf-8
# Required modules are imported and set up
import glob
import time
from time import sleep
import RPi.GPIO as GPIO
 
# At this point the pause between the individual measurements can be set
sleeptime = 1
 
# The One-Wire input pin is declared and the integrated PullUp resistor is activated
GPIO.setmode(GPIO.BCM)
GPIO.setup(4, GPIO.IN, pull_up_down=GPIO.PUD_UP)
 
# After activation of the Pull-UP resistor it waits
# until the communication with the DS18B20 sensor is established.
print ("Waiting for initialization...")
 
base_dir = '/sys/bus/w1/devices/'
while True:
    try:
        device_folder = glob.glob(base_dir + '28*')[0]
        break
    except IndexError:
        sleep(0.5)
        continue
device_file = device_folder + '/w1_slave'
 
 
# Function is defined, with which the current measured value can be read out at the sensor.
def TemperaturMessung():
    f = open(device_file, 'r')
    lines = f.readlines()
    f.close()
    return lines
 
# For initialization, the sensor is read out "blind" once.
TemperaturMessung()
 
# The temperature evaluation: On the Raspberry Pi, detected one-Wire slaves are assigned to a separate subfolder in the folder
# /sys/bus/w1/devices/ are assigned to an own subfolder. In this folder is the file w1-slave
# in which the data sent over the one-wire bus is stored.
# In this function these data are analyzed and the temperature is read out and output.
def TemperaturAuswertung():
    lines = TemperaturMessung()
    while lines[0].strip()[-3:] != 'YES':
        time.sleep(0.2)
        lines = TemperaturMessung()
    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
 
# Main program loop
# The measured temperature is output to the console - between the individual measurements
# is a pause, the length of which can be set with the "sleeptime" variable
try:
    while True:
        print ("---------------------------------------")
        print ("Temperature:", TemperaturAuswertung(), "degC")
        time.sleep(sleeptime)
 
except KeyboardInterrupt:
    GPIO.cleanup()

Example program download

KY001-RPi.zip

To start with the command:

sudo python3 KY001-RPi.py

# Load libraries
import machine, onewire, ds18x20
from time import sleep

# Initialization of GPIO2
ds_pin = machine.Pin(10)

# Initialization of the sensor object
ds_sensor = ds18x20.DS18X20(onewire.OneWire(ds_pin))

# Search for all matching sensors
roms = ds_sensor.scan()

# Serial output
print("Found DS devices")
print("Temperature (°C)")

# Endless loop for continuous reading of the temperature
while True:
  ds_sensor.convert_temp()
  sleep(1)
  # Based on the number of compatible sensors found it will count up
  for rom in roms:
    # Serial output of the measured temperature
    print(ds_sensor.read_temp(rom))
  sleep(3)