Working With LM35 Temperature Sensor Using Arduino Uno

In my previous article I had explained that how to control your led using serial monitor and in this article I'll show you the working with temperature sensor. After that we will look into how to connect the LM35 Temperature Sensor to your arduino borad and how we can sketch the program for that and finally using the temperatures how we can control your LEDs. It's quiet an interesting topic.

 

Introduction

 

Before using the temperature sensor we want to know how could we convert the values between Celsius and Fahrenheit 

 

Forumula
 

°F = °C x 1.8 +32   //Fahrenheit

°C = (°F-32)/1.8  // Celsius   

 

(or) we can use the simple trick for the conversion °C * 2 and °F + 30, using this trick we can find the value of Celsius and Fahrenheit

 

STEP1: 

 

Requirements:

• Arduino Uno
• Bread board
• LM35 Temperature Sensor
• LED-2
• Some Wires 

STEP2:

 

Connection:


   Figure 1: LM35 Temperature Sensor

The Temperature Sensor has 3 pins:

• +Vc to 5v
• Vout to Analog-5
• Gnd to Gnd
• LED1 to 7
• LED2 to 6

After the completion of  connection we want to sketch the following code to the arduino board to identify the current temperature in the room.

 

STEP3:

 

Programming:

//Declare the variables
int temp;
int temppin = 5;
int led1 = 7;
int led2 = 6;
void setup()
{
    pinMode(led1, OUTPUT);
    pinMode(led2, OUTPUT);
    Serial.begin(9600); //BaudRate
}
void loop()
{
    temp = analogRead(temppin);
    float t = (temp / 1024.0) * 5000;
    float celsius = t / 10;
    float farh = (celsius * 9) / 5 + 32;
    //Celsius Temperature
    Serial.print("Temperature =");
    Serial.print(celsius);
    Serial.print("*C");
    Serial.println();
    delay(1000);
    if (celsius > 30)
    {
        digitalWrite(led1, HIGH);
    }
    else
    {
        digitalWrite(led2, LOW);
    }
    if (celsius < 30)
    {
        digitalWrite(led1, HIGH);
    }
    else
    {
        digitalWrite(led2, LOW);
    }
    //Farenhite Temperature
    /*
    Serial.print("Temperature =");
    Serial.print(farh);
    Serial.print("*F");
    Serial.println();
    if(celius<30)
    {
    digitalWrite(led1,HIGH); //Sets LED ON
    }
    else
    {
    digitalWrite(led2,LOW);  / /Sets LED OFF
    }
    if(celius>30)
    {
    digitalWrite(led1,HIGH);//Sets LED ON
    }
    else
    {
    digitalWrite(led2,LOW);//Sets LED OFF
    }
    */
}

OUTPUT: 

The following output of the room temperature is shown in the serial monitor screenshots below,





Explanation

Declare the variables first named temp, temppin, led1, led2, then move on to the function mode setup() and initialize the variables, pinModes, and loop() function it is fully based upon your condition that how it want to work. Inside the loop function we have some values,

1. temp=analogRead(temppin); //Read Vout from LM -35 at analog pin 5
2. float t=(temp/1024.0)*5000; //Convert analog data to the  Celsius Reading
3. float celsius=t/10; 
4. float farh=(celsius*9)/5+32; //Convert Celsius Reading to the Fahrenheit

And then we want to glow your LED based up on the room temperature. For that here we are using IF conditional statement if(celsius>30), then led1 want to glow ,else led2 want to glow. Based upon your own conditions the led will work automatically.

 

Conclusion: 

 

And finally we conclude that we made Automated temperature based led on and off system.