Temperature and Humidity Monitoring Using SHT25 and Arduino

We have recently worked on various projects which required temperature and humidity monitoring, and then we realized that these two parameters actually play a pivotal role in having an estimate of the working efficiency of a system. Both for industrial and personal systems, an optimum temperature level is the requisite for the adequate performance of some systems.

This is the reason, in this tutorial, we are going to explain the working of the SHT25 humidity and temperature sensor with Arduino Nano.

Step 1: SHT25 Overview

First of all, let's start with the basic understanding of the sensor and the protocol on which it works.

SHT25 I2C Humidity and Temperature Sensor ±1.8%RH ±0.2°C I2C Mini Module: it is high-accuracy humidity and temperature sensor has become an industry standard in terms of form factor and intelligence, providing calibrated, linearized sensor signals in digital and I2C format. Integrated with a specialized analog and digital circuit, this sensor is one of the most efficient devices to measure the temperature and humidity.

The communication protocol on which the sensor works is I2C. I2C stands for the inter-integrated circuit. It is a communication protocol in which the communication takes place through SDA (serial data) and SCL (serial clock) lines. It allows connecting multiple devices at the same time. It is one of the simplest and most efficient communication protocols.

Step 2: What you need

The materials that we need for accomplishing our goal includes the following hardware components:

1. SHT25 humidity and temperature sensor

2. Arduino Nano

3. I2C Cable

4. I2C Shield For Arduino nano

Step 3: Hardware Hookup:

The hardware hookup section basically explains the wiring connections required between the sensor and the Arduino Nano. Ensuring correct connections is a basic necessity while working on any system for desired output. So, the requisite connections are as follows:

• The SHT25 will work over I2C. Here is the example wiring diagram demonstrating how to wire up each interface of the sensor.

• Out-of-the-box, the board is configured for an I2C interface; as such, we recommend using this hookup if you’re otherwise agnostic. All you need is four wires!

Only four connections are required Vcc, Gnd, SCL and SDA pins and these are connected with the help of I2C cable. These connections are demonstrated in the pictures above.

Step 4: Temperature and Humidity Monitoring Code

Lets start with the Arduino code now.

While using the sensor module with the Arduino, we include the Wire.h library. This library contains the functions which facilitate the I2C communication between the sensor and the Arduino board. The entire Arduino code is given below for the convenience of the user:

#include
// SHT25 I2C address is 0x40(64)
#define Addr 0x40
void setup()
{  
// Initialise I2C communication as MASTER  
Wire.begin();  
// Initialise serial communication, set baud rate = 9600  
Serial.begin(9600);  
delay(300);
}
void loop()
{  
unsigned int data[2];  
// Start I2C transmission  
Wire.beginTransmission(Addr);  
// Send humidity measurement command, NO HOLD master  
Wire.write(0xF5);  
// Stop I2C transmission  
Wire.endTransmission();  
delay(500);
// Request 2 bytes of data  
Wire.requestFrom(Addr, 2);
// Read 2 bytes of data  
// humidity msb, humidity lsb  
if(Wire.available() == 2)  
{    
data[0] = Wire.read();    
data[1] = Wire.read();
// Convert the data    
float humidity = (((data[0] * 256.0 + data[1]) * 125.0) / 65536.0) - 6;
// Output data to Serial Monitor    
Serial.print("Relative Humidity :");    
Serial.print(humidity);    
Serial.println(" %RH");  
}
// Start I2C transmission  
Wire.beginTransmission(Addr);  
// Send temperature measurement command, NO HOLD master  
Wire.write(0xF3);  
// Stop I2C transmission  
Wire.endTransmission();  
delay(500);
// Request 2 bytes of data  
Wire.requestFrom(Addr, 2);
// Read 2 bytes of data  
// temp msb, temp lsb  
if(Wire.available() == 2)  
{    
data[0] = Wire.read();    
data[1] = Wire.read();
// Convert the data    
float cTemp = (((data[0] * 256.0 + data[1]) * 175.72) / 65536.0) - 46.85;    
float fTemp = (cTemp * 1.8) + 32;
// Output data to Serial Monitor    
Serial.print("Temperature in Celsius :");    
Serial.print(cTemp);    Serial.println(" C");    
Serial.print("Temperature in Fahrenheit :");    
Serial.print(fTemp);    
Serial.println(" F");  
}  
delay(300);
}

All you need to do is burn the code in Arduino and check your readings on serial port. The output is shown in the picture above.

Step 5: Applications:

SHT25 temperature and relative humidity sensor has various industrial applications like temperature monitoring and computer peripheral thermal protection. We have also employed this sensor into weather station applications, as well as greenhouse monitoring system.