Arduino Temperature Sensor Using LM35

Introduction

The LM35 series are precision integrated-circuit temperature devices with an output voltage linearly proportional to the Centigrade temperature. LM35 is three terminal linear temperature sensor from National semiconductors. It can measure temperature from -55 degree Celsius to +150 degree Celsius. The voltage output of the LM35 increases 10mV per degree Celsius rise in temperature. LM35 can be operated from a 5V supply and the stand by current is less than 60uA. The pin out of LM35 is shown in the figure below.

Features

• Calibrated Directly in Celsius (Centigrade)

• Linear + 10-mV/°C Scale Factor

• 0.5°C Ensured Accuracy (at 25°C)

• Rated for Full −55°C to 150°C Range

• Suitable for Remote Applications

• Low-Cost Due to Wafer-Level Trimming

• Operates from 4 V to 30 V

• Less than 60-μA Current Drain

• Low Self-Heating, 0.08°C in Still Air

• Non-Linearity Only ±¼°C Typical

• Low-Impedance Output, 0.1 Ω for 1-mA Load

PinOuts Of LM35 is Shown in image.

You can download the datasheet from below file.

Step 1: Hardware Required and Circuit Diagram

• Arduino Board (Any) Buy it from Flipkart
• LM35 Sensor Buy it from Flipkart
• BreadBoard

Connect the Circuit as shown in image and upload the following code.

Step 2: Programming the Arduino

/*Code designed by Sujay Alaspure in SA Lab */

const int sensor=A5; // Assigning analog pin A5 to variable 'sensor'

float tempc; //variable to store temperature in degree Celsius

float tempf; //variable to store temperature in Fahreinheit

float vout; //temporary variable to hold sensor reading

void setup() {

pinMode(sensor,INPUT); // Configuring sensor pin as input

Serial.begin(9600);

}

void loop() {

vout=analogRead(sensor); //Reading the value from sensor

vout=(vout*500)/1023;

tempc=vout; // Storing value in Degree Celsius

tempf=(vout*1.8)+32; // Converting to Fahrenheit

Serial.print("in DegreeC=");

Serial.print("\t");

Serial.print(tempc);

Serial.print(" ");

Serial.print("in Fahrenheit=");

Serial.print("\t");

Serial.print(tempf);

Serial.println();

delay(500); //Delay of 1 second for ease of viewing }

Step 3: Output Result

See the result on Serial Moniter....

First of all, I would like to thank you for reading this guide ! I hope it helps you.

If You have any queries I am happy to help you.....

Drop a Comment. Your feedback is valuable for me.

Comments

[tgray1]

Hooked up as shown, vout fluctuates wildly (0 to 128), as do the temperatures. Is it possible the LM35 is defective?

[neodali]

My reading is:
in DegreeC= 291.99 in Fahrenheit= 557.59
in DegreeC= 291.99 in Fahrenheit= 557.59
in DegreeC= 291.99 in Fahrenheit= 557.59
in DegreeC= 291.99 in Fahrenheit= 557.59
in DegreeC= 291.99 in Fahrenheit= 557.59
in DegreeC= 291.99 in Fahrenheit= 557.59
in DegreeC= 291.99 in Fahrenheit= 557.59

what's the problem ?

[alusinehjalloh11]

Thanks very much for sharing this knowledge with the public. I am facing a challenge to integrate LM35 and heartbeat sensor. Whenever I integrate it, the temperature value will be incorrect, it will start to read 40, 52, 21 degree celcuis instead of 27.
How can I solve this problem?
Thanks for your understanding

[tgray1]

Clear and simple, easy to follow. But why does the temperature reading fluctuate so much?

[49DAVE]

Can u make a video using arduino nano, buzzer and lm35 sensor ? It should start z buzzer when a certain temp is reached .

[Jim0000]

Sujay,
Is there a sensor that could be used with this circuit and code that will have a temperature range up to 200 deg. C?
I need one for monitoring a two stroke engine head temperature.
Thanks for the page.
Jim.

[RavinderK19]

Why we are using 500

[GghV]

It doesn't work for me either. Temperature keeps changing from 30-40 to zero and back to 30-40 C. Maybe my LM35 is faulty?

[gabimal_ro]

Hi Sujay, thanks for posting this! Quick question: I did this schematic but the temperature is not showed correctly. I got variations between 120-202 Celsius on room temperature.

I actually tried several schematics with LM35 but I got the same results. I'm using an arduino nano with atmel 328P chipset if matters.

Any idea why is not working correctly? Thank you!

[salab]

you should check LM35 pin outs properly. if you connect it in wrong manner. it will not give proper output. Else there should not any issue.

[DIY Hacks and How Tos]

Nice tutorial. You should enter this in the Arduino contest.