Working With LM35 Temperature Sensor Using Arduino Uno

Kumaresh Rajalingam

IoT Arduino UnoArduinoTemperature SensorLM35 Temperature Sensor

15 Comments

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Gowtham Rajamanickam10y ago
Very good article
Kumaresh Rajalingam10y ago
Thank you santhakumar sir
Dr.Venkatesan Balakrishnan10y ago
Good work Kumaresh. I joined because of your motivation :)
- Kumaresh Rajalingam10y ago
  Thank u so much sir.....
Kumaresh Rajalingam10y ago
Thank you sir
Santhakumar Munuswamy10y ago
Good work. Keep it up
Kumaresh Rajalingam10y ago
Thanks joe wilson sir
Kumaresh Rajalingam10y ago
Thanks karthiga Madam
Kumaresh Rajalingam10y ago
Thanks Ankit Bansal sir
Kumaresh Rajalingam10y ago
Thanks Gowtham Rajamanickam sir
Joe Wilson10y ago
Thank you for sharing.
Sr Karthiga10y ago
cool
Ankit Bansal10y ago
Thanks for sharing
Gowtham Rajamanickam10y ago
good article..
Gowtham Rajamanickam10y ago
good article..

In my previous article, I had explained 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 board 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

Formula

°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 the 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 wants to work. Inside the loop function, we have some values,

temp=analogRead(temppin); //Read Vout from LM -35 at analog pin 5
float t=(temp/1024.0)*5000; //Convert analog data to the Celsius Reading
float celsius=t/10;
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 the system.