Temperature Sensor using PIC16F877A Microcontroller

Temperature measurement is a crucial aspect in numerous applications, spanning from weather monitoring to industrial processes. The ability to accurately and efficiently measure temperature plays a vital role in ensuring the optimal performance and safety of various systems. In this article, we will explore the implementation of a digital temperature measurement system using a microcontroller. By utilizing components such as the PIC16F887A microcontroller, LM35 temperature sensor, and an LCD display, we will look into the circuitry, code, and practical aspects of this project.

Components

To build this system, we require the following components:

1. PIC16F877A Microcontroller

The PIC16F877A microcontroller is a powerful and easy-to-program 8-bit microcontroller. It features 256 bytes of EEPROM data memory and self-programming capabilities. The operating voltage range is between 2V and 5.5V, making it versatile for various projects. It also includes 2 comparators, a 10-bit Analog-to-Digital Converter (ADC), and PWM functions, making it suitable for interfacing with LCDs and sensors.

2. Pickit 3 Programmer

To program the PIC16F877A microcontroller, we require a Pickit 3 programmer. This programmer is compatible with the MPLAB Integrated Programmer Environment (IPE) and allows for easy programming of the microcontroller.

3. LCD 16×2 Display

A 16×2 LCD display is used to show the temperature readings. It consists of 16 pins and requires a 10K ohm potentiometer to adjust the contrast. The display also includes a backlight LED. The LCD is capable of displaying 16 characters in two lines, providing sufficient space for temperature display.

4. LM35 Temperature Sensor

The LM35 is an inexpensive yet precise temperature sensor. It has a temperature measurement range between -50°C to 150°C and operates from 4V to 30V, consuming less than 60μA current. Compared to other temperature sensors, the LM35 is more efficient, as it is made up of an integrated circuit with no risk of damaging internal circuitry. Additionally, it draws current only in micro Amperes, making it ideal for portable projects.

Others

Other components required for this project include a breadboard, jumper wires, and a 10K ohm potentiometer.

LM35 Temperature Sensor Interfacing with Pic Microcontroller

The LM35 temperature sensor converts temperature into an analog voltage value. Pin one and three of the LM35 are connected to the 5-volt power supply, whereas pin two outputs the analog voltage proportional to the temperature value. The relationship between the measured temperature and the analog output voltage is 1°C = 10mV.

To measure the analog voltage value, we use the PIC16F887A microcontroller’s built-in ADC. The microcontroller has seven built-in ADC channels, allowing for easy interfacing with multiple sensors. After reading the ADC value, the voltage is converted back into temperature using a conversion factor. The temperature value is then displayed on the LCD, which is connected to PORTB of the microcontroller.

Circuit Diagram

The circuit diagram for the digital temperature sensor is shown below:

The circuit diagram illustrates how the components, including the PIC16F877A microcontroller, LM35 temperature sensor, and LCD display, are interconnected to form a complete temperature measurement system. By using the microcontroller’s analog-to-digital converter (ADC) to read the voltage from the LM35 temperature sensor and utilizing specific code, the temperature value can be converted and displayed on the LCD screen.

temperature sensor circuit diagram

To protect the LM35 and microcontroller, it is recommended to connect an 80K ohm resistor in parallel to the output of the temperature sensor.

NOTE: Before starting this project, it is recommended to learn about LCD interfacing with a Pic microcontroller, especially the hardware part. Understanding this will help avoid any issues during the project implementation.

Code

The code for this project is written in the MIKROC compiler. It includes sections for reading the temperature, converting the data, and displaying it on the LCD. If you do not know how to use MikroC for Pic, you can refer to these tutorials:

In programming part conversion factor is used to convert voltage back into temperature.The conversion factor is:

  • 1 volt = 100 degree
  • temp   = ( Output voltage * 100 oC/V )
  • Code is written in MIKRO C compiler.
// LCD module connections
sbit LCD_D7 at RB2_bit;
sbit LCD_D6 at RB3_bit;
sbit LCD_D5 at RB4_bit;
sbit LCD_D4 at RB5_bit;
sbit LCD_EN at RB6_bit;
sbit LCD_RS at RB7_bit;

sbit LCD_D7_Direction at TRISB2_bit;
sbit LCD_D6_Direction at TRISB3_bit;
sbit LCD_D5_Direction at TRISB4_bit;
sbit LCD_D4_Direction at TRISB5_bit;
sbit LCD_EN_Direction at TRISB6_bit;
sbit LCD_RS_Direction at TRISB7_bit;

int temp;
char temper[7];

void READ_temp(void)
{
    temp = ADC_Read(0);
    temp = temp * 5/1023;
    temp = temp * 100;
}

void data_conversion(void)
{
    inttostr(temp, temper);
}

void display_temperature(void)
{
    lcd_out(1, 1, "TEMPERATURE=");
    lcd_out(1, 13, Ltrim(temper));
    Lcd_Chr_Cp(0xdf);
    Lcd_Chr_Cp('C');
    Lcd_Chr_Cp(' ');
}

void main()
{
    ADC_Init();
    Lcd_Init(); // Initialize LCD
    Lcd_Cmd(_LCD_CLEAR); // Clear display
    lcd_cmd(_LCD_CURSOR_OFF);
    lcd_out(1, 4, "DIGITAL TEMPERATURE");
    lcd_out(2, 6, "SENSOR");
    delay_ms(1000);
    Lcd_Cmd(_LCD_CLEAR); // Clear display

    while(1)
    {
        READ_temp();
        data_conversion();
        display_temperature();
    }
}

How Does Code Work?

Here’s an explanation of each line of code:

// LCD module connections
sbit LCD_D7 at RB2_bit;
sbit LCD_D6 at RB3_bit;
sbit LCD_D5 at RB4_bit;
sbit LCD_D4 at RB5_bit;
sbit LCD_EN at RB6_bit;
sbit LCD_RS at RB7_bit;

sbit LCD_D7_Direction at TRISB2_bit;
sbit LCD_D6_Direction at TRISB3_bit;
sbit LCD_D5_Direction at TRISB4_bit;
sbit LCD_D4_Direction at TRISB5_bit;
sbit LCD_EN_Direction at TRISB6_bit;
sbit LCD_RS_Direction at TRISB7_bit;

These lines define the connections between the PIC microcontroller and the LCD module. The sbit keyword is used to define individual bits of the microcontroller’s ports (RB2, RB3, RB4, RB5, RB6, RB7) as corresponding pins of the LCD module. The sbit LCD_D7_Direction at TRISB2_bit; lines set the direction of the LCD pins as output.

int temp;
char temper[7];

Here, two variables are declared: temp to store the temperature value and temper, an array of characters to store the converted temperature value.

void READ_temp(void)
{
    temp = ADC_Read(0);
    temp = temp * 5/1023;
    temp = temp * 100;
}

This function reads the temperature value from the ADC (Analog-to-Digital Converter) channel 0. The ADC_Read(0) function returns a value in the range of 0 to 1023, which represents the analog voltage value. The temp value is then converted to temperature by multiplying it with a conversion factor.

void data_conversion(void)
{
    inttostr(temp, temper);
}

This function converts the integer temperature value (temp) into a string format (temper) using the inttostr() function. It enables the temperature value to be displayed on the LCD.

void display_temperature(void)
{
    lcd_out(1, 1, "TEMPERATURE=");
    lcd_out(1, 13, Ltrim(temper));
    Lcd_Chr_Cp(0xdf);
    Lcd_Chr_Cp('C');
    Lcd_Chr_Cp(' ');
}

This function displays the temperature value on the LCD. The lcd_out() function is used to output the string “TEMPERATURE=” at the specified position on the LCD (line 1, column 1). The Ltrim() function is used to remove any leading spaces from the temper string. The Lcd_Chr_Cp() function is used to display the degree symbol (0xdf) followed by the letter ‘C’ on the LCD.

void main()
{
    ADC_Init();
    Lcd_Init(); // Initialize LCD
    Lcd_Cmd(_LCD_CLEAR); // Clear display
    lcd_cmd(_LCD_CURSOR_OFF);
    lcd_out(1, 4, "DIGITAL TEMPERATURE");
    lcd_out(2, 6, "SENSOR");
    delay_ms(1000);
    Lcd_Cmd(_LCD_CLEAR); // Clear display

    while(1)
    {
        READ_temp();
        data_conversion();
        display_temperature();
    }
}

The main() function is the entry point of the program. It initializes the ADC and LCD by calling the ADC_Init() and Lcd_Init() functions, respectively. The Lcd_Cmd(_LCD_CLEAR) function is used to clear the LCD display. The lcd_cmd(_LCD_CURSOR_OFF) turns off the cursor on the LCD. The lcd_out() functions are used to output the specified strings on the LCD. After a brief delay, the while loop starts, continuously reading the temperature, converting it, and displaying it on the LCD.

Demonstration

To fully simulate and obtain the hex file for this project, please refer to the following link: Temperature Sensor using PIC Microcontroller.

Conclusion

Implementing a digital temperature measurement system using a microcontroller provides a cost-effective and accurate solution. By utilizing the LM35 temperature sensor and the PIC16F887A microcontroller, it is possible to measure and display temperature readings with ease.

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169 thoughts on “Temperature Sensor using PIC16F877A Microcontroller”

  3. hi malik,
    thank you for this good job, i don’t understand the function Ltrim and how to display a negative temperature
    thanks a lot

    Reply

  7. I am doing my project on load cell, in that i want to display load cell ouput voltage into load value,for that i am using PIC16f877a..Anyone pls help me

    Reply

  16. its a good thing to find your blog today!!

    I want to do two projects;
    first; i wants to measure and display room temperature and humidity at real-time , or every 2seconds, I need one pin to be high and low at 1hr intervals,
    Also i want one pin to be high for only 5 seconds after every 2hrs,

    these are for alarms, one pin high per each condition ,when temperature is at 34c, 36c, 38c 39c and 39.5c
    in case of humidity, one pin high per each condition , when humidity is at 50%, 60% and 70%

    I want it to control my homemade incubator , I hope you can add to a certain pins which will control the heaters for generating temperature and humidity default temp. is 37.8c and humidity is 65%, so any deviation from these defaults the pins assigned will act accordingly from there it will stabilizer the condition

    is it possible to add several buttons for setting the completed unit? if possible it will be awesome to include. Please kindly suggest the circuit diagram and the codes.

    Let me end here with only the first .

    Sorry for my bad English, I am from Africa, Tanzania. I am waiting for you to inbox me via nziku99@gmail.com , thanks in advance

    Reply

  19. Hey there,
    I wish to add a keypad to this same project, such that, message on the lcd ask me press (*),
    Then ” Enter Code”. If the right code is entered, then the temperature is displayed.
    if Wrong code is entered, Code error message is displayed.
    Can you please help with a complete source code?

    Reply

  23. Dear Sir,

    I am Shrikant M and Pursuing B.E final year. I came across your site
    and it’s really to say that your web site is amazing which provides
    new trends techno project ideas. So, I am doing project on the title
    “Temperature control in PROTEUS using ADC with motor attached to it”.
    Its like when temperature is high then RPM of motor should be more and
    vise versa. In addition to that I needed to add any feature by adding
    TRANSISTOR. But I am not getting sir. Please help me out this. I saw
    your all projects So, your one of the expert.

    Please send me the design of such project and its C-code. I am using
    8051 or 8951. Please send me ADC-Motor-LCD-TRANSISTOR-Any other
    feature. Please send sir and your help will be like star for me.

    Thanking You,

    Shrikant M
    shrshr03@rediffmail.com

    Reply

      • Dear Sir,

        My logic is that
        — –> From 0-19 Celsius, Fan OFF and Heater ON
        — –> 20-25 Normal Temp. Fan OFF and Heater OFF
        — –>26-30 Fan ON at 1 level
        — –> More than 30, Fan level 2.

        With above logic I wanted to add one more feature. I am not getting sir. So, I am seeking help from you because you the one who can help me out. Project dates are very near sir. I wanted in Embedded C program. I am using Keil software. Please check my previous circuit. Kindly, help me out.
        Thanking You,
        Shrikant M
        shrshr03@rediffmail.com

        Reply

  24. i have a couple of questions:
    what is the range of temperature which can be sensed?
    is this similar to the thermometer?

    Reply

  27. it is a good project .i need temperature sensor project with buzzer which beep at above 40 c using pic18f452 in assembly languange .

    Reply

  29. Hi! I downloaded all the files and simulated it. But there is no display in the lcd, just the white background indicating that it is running. But no texts display. Pls help

    Reply

  33. hey men. i have a troubble in the communicate tempreature. when you read the tempreatue on the LCD . it send the values to your computer an you can read on the computer. Help me! thanks!

    Reply

  40. Hello!
    I would like to know the full components package for “automatic speed control of ac fan using triac,temperature sensor lm35 and,and pic microcontroller”.

    Reply

  41. sir can i have the code for air pollution detection system using pic16f877a where sulpher dioxide carbon monoxide sensors are interfaced to controller and readings of sensors are compared with threshold values

    Reply

  45. Assalamualaikum,
    Sir ,this project is very good.I want to try it as a project in university , please send me programming file of “Temperature sensor using PIC16F877A microcontroller” in micro c compiler .Please send me urgent and my email is umar.13253@gmail.com.
    Thanks

    Reply

  46. this code is working in the proteus software but not in circuit. can u please help us to fix this problem.
    we use MPLAB XC8 compiler and PIC16F877A.
    my Email address- b.kiru29@gmail.com
    i have to submit my project with in two weeks.

    #define _XTAL_FREQ 4000000
    #include
    #include
    #include
    #include
    #pragma config FOSC = HS // Oscillator Selection bits (HS oscillator)
    #pragma config WDTE = OFF // Watchdog Timer Enable bit (WDT disabled)
    #pragma config PWRTE = OFF // Power-up Timer Enable bit (PWRT disabled)
    #pragma config BOREN = OFF // Brown-out Reset Enable bit (BOR enabled)
    #pragma config LVP = OFF // Low-Voltage (Single-Supply) In-Circuit Serial Programming Enable bit //(RB3/PGM pin has PGM function; low-voltage programming enabled)
    #pragma config CPD = OFF

    void main() // main program begins
    {
    double value;
    TRISD=0b00000000;
    TRISA = 0b11111111; // initialize Port A as an input port
    TRISC = 0b00000000; // initialize Port C as an Output port
    PORTC = 0b00000011;// exhaust fan switches on

    PORTD= 0b00000000;
    while(1)
    {

    ADCON0 = 0b11000101;

    ADCON1 = 0b10000000;

    while(GO_DONE);

    value = (ADRESH <75.0)
    {
    PORTC = 0b00001100;
    __delay_ms(5000);
    }

    }

    }

    Reply

  47. hi bilal
    help me codes in microcontroller based power factor correction .
    i`m using pic16f877a microcontroller. it is my final year project

    Reply

  50. Sir, I’m a final year student working on a project that requires to take temperature as input and identify whether the temperature is withing admissible range. please help me out with this.
    also, if you can send the hex file and simulation of the project, it would be very helpful.
    namgem.11@gmail.com

    Reply

  52. Can you please send me the hex file and circuit diagram and other details.i am working on project similar to this.
    @azimahabdullah20@gmail.com

    Reply

  54. please mail me the source code for the project temperature automatic fan speed control system using PIC16F877A. I can send u the circuit diagram for this. please sir, its very urgent.

    Reply

  55. Sir, please can u kindly send me the simulation and the programming file compiled in Mikro C of this project. I am working on a similar one and I need u to help me out please. I have few works to submit it, so kindly email me the details- joembia1@gmail.com

    Reply

  56. Dear,
    I have copied each and every bit of your project but lcd display shows 0 degree centigrade. i have checked the code and connections twice but could not find anything wrong. what is the issue.

    Reply

  57. hi dear Bilal Malik
    I can´t find the display working to show the setup data to many kind of display Models using with PIC16F877A.
    the programming method I am using are Flowcode 6 & Flowcode 7 with EB-006-00-8. programming module. every thing shows ok from my Laptop but this small mistake in setting the programming configuration is not correct .now I say it is for a long time I am searching for a solution for this problem.
    the outputs configuration has been a problem with me in many of my privet projects.
    looking forward to hear from you if there is any solution

    Reply

  59. I want to know why you have added the external crystal, capacitors, and the resistors. Please tell the function of these external components.

    Reply

    • The crystal gives the oscillator frequency the micro controller will be using as a clock to perform the operations. The capacitors are to absorb noise from the power, and they are chosen according to the crystal speed. The resistor is to hold the MCLR pin on high, so it runs, and it’s a high resistor so the current that flows there is super low, so the micro controller doesn’t get damaged.

      Reply

  63. Please send me an email of this program because it doesn’t seem to run on the one I built; I’m using v6.6.1 of mikroPC and proteus 8.

    Reply

  76. sir,
    How the source code will change, if I use HIGH-TECH ANSI compiler. Please send source code for that compiler.

    Reply

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    and it has helped mе out loads. I hope tօ give a
    contribution & assist Ԁifferent customers ⅼike itѕ aided me.

    Good job.

    Reply

  79. sir can you help me with me thesis about battery management system.
    that can monitor voltage, current, state of charge of individual battery

    Reply

  82. I’m using pic16F877A n LM35 sensor with CCS compiler to coding for this project. Someone who need the hex file or full code n simulation file on Proteus, just leave your Email, I’ll send it to you.

    Reply

  89. hi can i have the hex file am also working on the same project and it REALLY would be helpful for my project if you just send me the file please

    Reply

  99. hi mr.bilal this is really good job. i dont understand the part that i attached below.
    void display1(void)
    {
    lcd_out(1,1,”TEMPERATURE=”);
    lcd_out(1,13, Ltrim(temper));
    Lcd_Chr_Cp(0xdf);
    Lcd_Chr_Cp(‘C’);
    Lcd_Chr_Cp(‘ ‘);

    }
    can you pls help me. my mail id is sripriya.dharshini@yahoo.com
    pls do the neeedfull mr.bilal.

    Reply

  104. I need project circuit diagram and code of project with hex file for digital thermometer using pic16f877a and lm35 sensor with LCD display.

    Reply

  105. I need project circuit diagram and code of project with hex file for digital thermometer using pic16f877a and lm35 sensor with LCD display.

    Reply

  106. Sir after running the code , hex file is being created but while opening it the file is not opening and a message of : FILE NOT FOUND is being shown up. Please help me with it.

    Reply

  120. Hello sir. Can I please have the whole code of an automatic temperature controller as per circuit. I learning this language and I’m using proteus 8.

    Reply

  122. hello sir ,can i get the code in assembly language? and is there a code that support humidity sensor with tempreture sensor in one circuit

    Reply

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