The Engineering Projects

Introduction to LM35

Hello friends, I hope you all are doing great. In today's tutorial, we are gonna have a look at a detailed Introduction to LM35. LM35  is a type of commonly used temperature sensor, that can be used to measure temperature with an electrical output compared to the temperature in (°C). In can measure temperature in a better way than a thermistor. LM35 is used in industries and commercial buildings where high accuracy of temperature measuring is needed. I will give you a detailed overview of this temperature sensor in today’s post where we will have a look its pinout, working, protocol, etc. I will also share some links of projects where I have interfaced it with Arduino or other microcontrollers. If you have any questions please ask in the comments, I will resolve your queries and will guide you in a comprehensive way. So, let’s get started with the basic Introduction to LM35:

Introduction to LM35

• LM35 is a commonly used temperature sensor, It shows values in the form of output voltages instead of degrees Celsius.
• LM35 shows higher voltage values than thermocouples and may not need the output voltage to be amplified.

• The output voltage of LM35 is proportional to the Celsius temperature. The scale factor is .01 V/°C.
• One most important characteristics is that it draws just 60 microamps from its supply and acquires a low self-heating capacity.
• LM35 temperature sensor available in many different packages like T0-46 metal transistor-like package, TO-92 plastic transistor-like package, 8-lead surface mount SO-8 small outline package.

Let's have a look at LM35 PINOUT configuration:

LM35 Pinout

• LM35 has three pinouts which are:
  • PIN 1: Vcc, it used as input at this pin we apply +5 V input voltage.
  • PIN 2: At this pin, we get output voltage.
  • PIN 3: This pin is used for ground.
• Here's the table for LM35 Pinout for better understanding:

 

No.	Parameter	Pin Type
1.	Vcc	Power Pin ( Connected to +5V )
2	Vout	Output Pin (It should be connected with an analog pin of Microcontroller)
3	Ground	Ground Pin ( Connected to 0V or GND )

For better understanding lets, have a look at LM35 Pinout figure. Let's have a look at working of LM35  Working.

Working of LM35

• LM35 is used to measure precise centigrade temperature. The output of this sensor changes describes the linearity. The output voltages of this sensor are linearly comparative to the Celsius temperature.
• The output voltage range of this sensor is from -55° to +150°C. It also has low self-heating power.
• Its operating voltages is 4 to 30 volts.
• In the most circuit, this sensor is used with an operational amplifier. An amplifier is a device which amplifies applied a voltage at a certain level.
• Operational Amplifier has three terminal, first two are inverting and noninverting inputs third one is used for output.
• By using LM35 with operational amplifier we can get amplification of output voltages of LM35.
• For better understanding lets have a look at circuit diagram.

LM35 Features

• Its maximum and minimum input voltages are 35 V and -2 V respectively. It typically operates at 5 V.
• It can measure temperature from -55°C to 150°C.
• Its Output voltage is directly proportional (Linear) to temperature (i.e.) there will be a rise of 10mV (0.01V) for every 1°C rise in temperature.
• Its Drain current is less than 60 uA.
• Its low-cost temperature sensor.
• It is small and hence suitable for remote applications.
•  It is available in TO-92, TO-220, TO-CAN and SO IC package.
• It is low self-heating, 0.08 C in still air n Non-linearity only ±1/4C typical.

Parameters of LM35

Let's discuss some working parameters of LM35

No.	Parameter	Conditions	Value	Unit
1.	Accuracy LM35, LM 35C	T A=+25°C	±0.4	°C
2	Accuracy, LM35D	T A=+25°C	±0.6	°C
3	Non linearity	T MIN=TA=T MAX	±0.3	°C
4	Sensor Gain	T MIN=TA=T MAX	+10.0	mV/°C
5	Load Regulation	T A=+25°C	±0.4	mV/mA
6	Line Regulation	T A=+25°C	±0.01	mV/V
7	Quiescent Current	V S=+5V, +25°C	56	µA
8	Change of Quiescent Current	4V=VS=30V	0.2	µA
9	Temperature Coefficient of Quiescent Current	-	+0.39	µA/°C
10	Long Term Stability T J=T MAX, for 1000 hours	±0.08	±0.08	°C

 

LM35 Interfaced with Aurdino

Now, let's discuss LM35 interfacing with Arduino and design a simple project:

• The project which we are gonna discuss is Temperature Monitoring on Virtual Terminal of Arduino.
• Temperature Sensor we are gonna use is LM35.
• In this circuit, Aurdino is the main component because it controls all functions.
• In this circuit LM35 senses the temperature and converts into an electoral (analog) signal, then this signal applied to Microelectronic Unit through an analog-to-digital converter (ADC).
• The analog signal is converted into digital format by the ADC.
• The value of temperature sensed by the sensor will be displayed on Serial Terminal or virtual Terminal if you are working on Proteus.
• You can download this complete Proteus simulation from Interfacing of LM35 with Arduino in Proteus.
• I have also shared Interfacing of LM35 with PIC Microcontroller, so if you are working on PIC Microcontroller then you should read that out.
• For better understanding lets see the circuit diagram of this project:

Now, let's discuss the advantage and application of this project. Let's have a look at applications of LM35:

Applications of LM35

These are some applications of LM35, let discuss them.

• It's used for measuring the temperature of a particular environment.
• It provides thermal shutdown for a circuit or component used in a specific project.
• It can be used for battery temperature measurement. It provides battery protection from overheating.
• It can be used in HVAC applications as a temperature measurement device.

I hope you have enjoyed today's tutorial on this simple temperature sensor LM35. Let me know if you need any help with its projects. Will meet you guys in the next tutorial. Till then take care, have fun !!! :)

Interfacing of LM35 with Arduino in Proteus ISIS

Hello friends, I hope you all are fine and enjoying yourself. Today I am going to share a new project titled Interfacing of temperature sensor LM35 with Arduino UNO in Proteus ISIS. So far, I have only worked on temperature sensor DS18B20 for temperature measurements and I have also uploaded a tutorial on Interfacing of Temperature Sensor 18B20 with Arduino.

Recently I got a chance to work on a project regarding temperature sensing but the condition of this project was that to use only LM35 for temperature detection. Then, I get to know much about LM35, its operating conditions and features. So I thought I should also upload its tutorial as it will also be advantageous for engineering students. Because learning new things is always a charm.

An excellent thing about LM35 is that it's quite cheap as compared to other temperature sensors. And as it's cheap, that's why it's not very reliable, if you personally ask me then I will prefer DS18B20 over LM35 because of its accurate readings. Now, let's move towards its interfacing and its practical applications. First of all, let's have a quick look at the introduction of LM35 and then we will design it in Proteus ISIS.

Where To Buy?
No.	Components	Distributor	Link To Buy
1	LM35	Amazon	Buy Now
2	Arduino Uno	Amazon	Buy Now

Introduction of LM35 Temperature Sensor

• LM35 is an embedded sensor, used to measure the temperature of its surroundings and is famous because of its low cost.
• Its output is generated in the form of an Electrical signal and this electrical signal is proportional to the temperature, which it detects.
• Lm35 is much more sensitive than other temp measuring devices (not accurate).
• The internal circuitry of this embedded sensor is sealed inside a capsule.
• LM35 is a 3 pin IC and it is used for temperature detection. The physical appearance of LM35 is shown in the image given below:

• As you can see in the above image that LM35 is a 3 pin IC:
  1. The first pin is Vcc, so it should be connected to 5V.
  2. The center pin is its Data Pin and LM35 gives its output when it measures temperature.
  3. The third pin is GND and should be connected to the ground of the battery/source.

LM35 Arduino Interfacing

• As my today's tutorial is about interfacing LM35 with Arduino so let's start it.
• I have connected LM35 with Arduino microcontroller and it is shown in the image given below:

• As you can see in the above image, I have connected an LM35 sensor with Arduino UNO.
• The VCC pin of LM35 is connected to +5V of the Arduino board.
• Since LM35 generates an analog value at its output pin that's why I have connected this pin to the 'A0' pin of the Arduino board.
• This pin of Arduino board is used to receive analog data from an external source.
• And the last pin is connected to the GND pin of the Arduino board.

Arduino Code for LM35

• After connecting the circuit, now upload the below code to your Arduino board.

#define TempPin A0

int TempValue;

void setup()
{
  Serial.begin(9600); // Initializing Serial Port
}
void loop()
{
  TempValue = analogRead(TempPin); // Getting LM35 value and saving it in variable
  float TempCel = ( TempValue/1024.0)*500; // Getting the celsius value from 10 bit analog value
  float TempFarh = (TempCel*9)/5 + 32; // Converting Celsius into Fahrenhiet

  Serial.print("TEMPRATURE in Celsius = "); //Displaying temperature in Celsius
  Serial.print(TempCel);
  Serial.print("*C");
  Serial.print("    |    ");

  Serial.print("TEMPRATURE = "); // Displaying Temperature in Fahrenheit
  Serial.print(TempFarh);
  Serial.print("*F");
  Serial.println();
  
  delay(1000);

}

LM35 Arduino Simulation in Proteus ISIS

• Now let's do this project in Proteus. Proteus also has an LM35 sensor in its database which we are going to use here.
• Moreover, we also know about Arduino Library for Proteus V2.0, so using that library we are going to interface LM35 with Arduino in Proteus ISIS.
• First of all, design the same circuit as shown in the above figure in Proteus software as shown below:

• It's the same circuit as we designed before, the only addition is the virtual terminal. We are using it to check the values.
• It's simply like the Serial Monitor we use in Arduino software.
• So, now using the above code, create the hex file and upload it in Proteus.
• Now hit run and if everything goes fine then you will get results as shown in the below figure:

• You can see the Virtual Terminal is showing the same value as shown on the sensor which is 33 in Celsius and later I converted it to Fahrenheit.

It's quite simple and I have also commented on the code but still if you find trouble then ask in comments and I will resolve them. Will meet in the next tutorial, till then take care!!! :)