### Project 19 What’s the temperature

**1.Introduction**

In this lesson, we will combine DS18B20 Temperature Sensor and 1602 I2C Module to make a temperature measuring device. You can also apply the experiment principle to make a temperature alarm.

**2.Hardware required**

- EASY plug controller Board x1
- USB cable x1
- EASY plug cable x2
- EASY plug 1602 I2C Module x1
- EASY plug DS18B20 Temperature Sensor x1

Before we get to the test, let’s take a look at this DS18B20 Temperature Sensor.

![](media/image-20251126155051432.png)

This DS18B20 Temperature Sensor Module is not like traditional analog temperature sensors that need additional A/D and D/A conversion chip, placing a challenge on limited port resources of Arduino, this newly developped DS18B20 Temperature Sensor can be easily connected to an Arduino digital input. The sensor communicates over a one-wire bus and requires little in the way of additional components so users can easily create a sensor network. Below are its specifications:

- Supply Voltage: 3.3V to 5V
- Temperature range: -55 °C ~ +125 °C
- Interface: Digital
- Size: 40*20mm
- Weight: 3g

**3.Connection Diagram**

Now, connect the DS18B20 module to the D2 port of the controller board, and LCD module to IIC using the EASY plug cables.

![](media/image-20251126155204695.png)

**4.Sample Code**

Connect the board to your PC using the USB cable; copy below code into Arduino IDE, and click upload to upload it to your board.

```c
#include <OneWire.h>   // Place file “OneWire.h” under the directory “library” of Arduino
#include <Wire.h>    // Place file “OneWire.h” under the directory “library” of Arduino
#include <LiquidCrystal_I2C.h>   // Place file “LiquidCrystal_I2C.h” under the directory library of Arduino
 int DS18S20_Pin = 2; //DS18S20 Signal pin on digital 2
 //Temperature chip i/o
OneWire ds(DS18S20_Pin);  // on digital pin 2
LiquidCrystal_I2C lcd(0x27,16,2);  // set the LCD address to 0x27 for a 16 chars and 2 line display
 void setup(void) {
  Serial.begin(9600);
  lcd.init();                      // initialize the lcd 
  lcd.init();
  // Print a message to the LCD.
  lcd.backlight();
}
 void loop(void) {
  float temperature = getTemp();
{
  lcd.setCursor(1,0);
  lcd.print("temperature is");
  lcd.setCursor(3,1);
  lcd.print(temperature);
}
delay(2000);
}
float getTemp(){
  //returns the temperature from one DS18S20 in DEG Celsius
  byte data[12];
  byte addr[8]; 
  if ( !ds.search(addr)) {
      //no more sensors on chain, reset search
      ds.reset_search();
      return -1000;
  }
  if ( OneWire::crc8( addr, 7) != addr[7]) {
   {
   lcd.setCursor(3,0);
   lcd.print("CRC is ");
   lcd.setCursor(3,1);
   lcd.print(" not valid!");
   }
      return -1000;
  } 
  if ( addr[0] != 0x10 && addr[0] != 0x28) {
  {
  lcd.setCursor(3,0);
  lcd.print("Device is ");
  lcd.setCursor(3,1);
  lcd.print("not recognized");
  }
      return -1000;
  }
  ds.reset();
  ds.select(addr);
  ds.write(0x44,1); // start conversion, with parasite power on at the end
  byte present = ds.reset();
  ds.select(addr);    
  ds.write(0xBE); // Read Scratchpad
  for (int i = 0; i < 9; i++) { // we need 9 bytes
    data[i] = ds.read();
  }
  ds.reset_search();
  byte MSB = data[1];
  byte LSB = data[0];
  float tempRead = ((MSB << 8) | LSB); //using two's compliment
  float TemperatureSum = tempRead / 16; 
  return TemperatureSum;
}
```

**5.Result**

After power is on, LCD first line displays “temperature is”, second line displays the current temperature. Temperature is updated in 3 seconds interval.

![](media/image-20251126155332276.png)