Project Report- PID

ACKNOWLEDGEMENT

We have great pleasure in acknowledging our sincere gratitude to all who have been

given the helping hands in the successful completion of our project.

First of all, always we are thankful to Almighty GOD who had showered his blessings on

us and gave us strength for doing our project.

Next, we would like to extend out thanks to the Principal; Prof. Mohammad Ebrahim,

College of Applied Science, Kottayi for providing us best facilities and atmosphere

according to our interest for the successful completion and presentation of our project.

Then, we are most like to give our sincere gratitude to Miss Simi S and Mr Sooraj K B,

guides of our project for all valuable advice and good instruction provided to us. We

would like to extend our sincere gratitude to other lectures in Electronics department who

had been the strength and also for good guidance of our project.

We would like to thanks Mrs. Sukanya & Mr. Hashim, Laboratory Assistants, for all the

help given to us.

Last but not least we express our sincere thanks to our parents, our friends and all others

who gave valuable suggestions, constructive criticism and constant encouragement for

presenting this project as a valuable one.

All with God’s grace….!!!

PROJECT TEAM

Temperature PID Controller 2010 - 2011

ABSTRACT

Through our project we are showing the control of constant temperature according to the

desired value (set point) in a closed loop using PID controller system. For this, we are

using a microcontroller, a temperature sensor for sensing the temperature of the closed

loops. By using the microcontroller we compare the desired value with current value and

it is displayed in the LCD. Also to provide the constant temperature, Fan or Heater is

turned On or Off according with the variations of current temperature in oC from desired

setpoint.

Dept of Electronics CASK


CONTENTS

1. INTRODUCTION 1

2. BLOCK DIAGRAM 4

3. BLOCK DIAGRAM DESCRIPTION 5

4. OVERALL CIRCUIT DIAGRAM

5. COMPONENT LIST

6. OVERALL CIRCUIT DIAGRAM WORKING

7. DESIGNING OR DESCRIPTION OF EACH BLOCK

POWER SUPPLY DESCRIPTION

BLOCK DIAGRAM

CIRCUIT AND EXPLANATION

MICROCONTROLLER

PIN DIAGRAM

THE MAJOR FEATURES OF PIC

MICROCONTROLLER CIRCUIT

EXPLANATION

ADVANTAGES

APPLICATION

ARCHITECTURE

WHY PIC?

8. WHY PID?

9. TEMPERATURE SENSOR

FEATURES OF LM 35



10. LIQUID CRYSTAL DISPLAY

11. PCB

PCB DESIGNING

PCB LAYOUT

12. FIRMWARE IMPLEMENTATION

13. CONCLUSION

14. FUTURE SCOPE

15. BIBILIOGRAPHY

16. APPENDIX



INTRODUCTION

The objective of our project “TEMPERATURE PID CONTROLLLER” is

maintaining the constant temperature in a particular area using PID controller.

Whatever the process or the parameter (temp, flow, speed, ..) the principles of control are

similar. Input and output signals are specified in this project is digital. Control of a

process is achieved by means of a closed loop circuit. This project is prepared in order to

control the temperature of a furnace in the best and easiest possible way.

The control system is that means by which any quantity of interest in a machine,

mechanism or other equipment is maintained or altered in accordance with a desired

manner. Here we have used the closed loop system; that is the feedback system. The

feedback signal is derived from the output of the system. This signal gives the capability

to act as self correcting mechanism. The beneficial effects of the feedback in the system

with high loop gain. The controlled variable accurately follows the desired value and

also feedback in a control system greatly improves the speed of its response.

One of the primary purposes of using feedback in control system is to reduce the

sensitivity of the system to parameter variations.

The project deals with a simple aspect of giving information about the controlling of

temperature in a furnace. In this project we are developing a system, which can control

temperature of a furnace automatically. The system is be capable of taking decisions

accordingly of overheating of blast furnace and cooling of a furnace.

This project is done by using microcontroller (PIC 16F873A) which was developed by

microchip company with several features than processors with cheap cost. A temperature

LM 35 is used in sensing the temperature and relays like heater or fan are used for

adjusting the temperature with desired temperature value. The functions occurring are

displayed on the liquid crystal display.

In this system, it can implement any applications about controlling or monitoring the

temperature without any human effort.



BLOCK DIAGRAM


Micro-controller

PIC16F873A

Temperature sensor

(LM35)

Power supply

Micro keys

SET UP DOWN

RELAY

Heater

Fan

LCD Display


BLOCK DIAGRAM DESCRIPTION

The block diagram for “temperature PID controller” circuit consist of

IC LM 35

PIC 16F873A

POWER SUPPLY

RELAY

DISPLAY SECTION

A fixed three terminal voltage regulator has a regulated dc output voltage of 5v and

provide it to IC LM 35, PIC 16f873A, micro keys, relays and display section

Temperature sensing section consists of an IC LM 35 which acts as a transducer. It

senses the temperature and converts it into voltage as a scale of 1oC into 10mv.

At the heart of the circuit is microcontroller PIC 16F873A with many advantages and it is

available in RISC architecture.

The output of the microcontroller is give to the relays and display section.

Relays we used here are Heater and Fan; they are used for adjusting the obtained

temperature with the desired temperature value.

The display section, through the IC LM020L, that displays temperature. It is the main

observable part of this whole system.



OVERALL CIRCUIT DIAGRAM





LIST OF COMPONENTS

REGULATOR 7805

PIC 16F873A

LM35

LCD DISPLAY – LM020L

RELAYS (2)

CRYSTAL – 4MHz

MICROSWITCHES (4)

DIODES – 1N4007 (4)

CAPACITORS

C1 - 1000µF

C2 – 100µF

C3, C4 – 33pF

RESISTORS

R1 – 10k (4)

R2, R3 – 1k

TRANSFORMER

TRANSISTORS – BC548 (2)

OVERALL CIRCUIT DIAGRAM WORKING



The circuit shows microcontroller based temperature PID controller using temperature

sensor.

Microcontroller PIC 16F873A is the heart of the circuit. It is available in

RISC architecture. The PIC 16F873A is a mid-range 8-bit CPU optimized for Control

Applications. It has 35 instructions on chip flash program memory.

LM35 used as the temperature sensor. It sense the current temperature of a closed

loop and converts into corresponding voltage as it is a transducer. It is connected to

pin 2 (RA0/AN0) of microcontroller. The microcontroller circuit is connected with

reset circuit and crystal oscillator circuit. Crystal oscillator is the one used to

generate the pulses to the microcontroller and it is also called as the heart of

microcontroller. Here we have used 4 MHz crystal which generates pulses. It offers

the highest precision (exactness/accuracy) and stability.

Even the microcontroller has an internal RC oscillator with a maximum frequency

of 4 MHz, noise affect it easily. Because of increasing of aging of oscillator,

resonant frequency varies and cannot get the fixed frequency. So we use crystal

oscillator externally for accuracy.

To set up the desired temperature value, we use the micro keys such as SET, UP,

DOWN. And also the tolerance value is set in the firmware using embedded C

language.

According to the comparison of desired temperature (here we say as ‘Set point’) with the

current temperature, the relay - Heater or Fan is worked.



Case I:

If the current temperature is greater than desired temperature (including tolerance) then

turn off the heater and turn on the fan.

Case II:

If the current temperature is less than the desired temperature (including tolerance), then

turn on the heater and turn off the fan.

Case III:

Else turn off both heater and fan.

The relays such as heater connected to pin 25 (RB4) and fan is connected to pin 26

(RB5).

The processing of controller will display in the LCD. The current temperature as ‘CT’

and the set point as ‘SP’can be observed on the first line of LCD. And also, the present

conditions of the relays are displayed on the second line of the LCD.



DESCRIPTION OF EACH BLOCK



POWER SUPPLY DESCRIPTION

BLOCK DIAGRAM

The ac voltage, typically 220V ms, is connected to a transformer, which steps

that ac voltage down to the level of the desired dc output. A diode rectifier then

provides a full-wave rectified voltage that is initially filtered by a simple capacitor

filter to produce a dc voltage, this resulting dc voltage usually has some ripple or ac

voltage variation.

A regulator circuit removes the ripples and also remains the same dc value

even if the input dc voltage varies, or the load connected to the output dc voltage

changes. This voltage regulation is usually obtained using one of the popular voltage

regulator IC units.

Block diagram (Power Supply)


Transformer(Step down)

Rectifier Filter IC Regulator

Load


CIRCUIT AND EXPLANATION

WORKING PRINCIPLE

TRANSFORMER

The transformer will step down the power supply voltage (0 – 230 V) to (0-

6V) level. Then the secondary of the potential transformer will be connected to the

center-tapped full-wave rectifier; where diodes are working in the property of one-

side conduction capability.

CENTER-TAPPED RECTIFIER

In a rectifier, a center-tapped transformer and two diodes can form a full-

wave rectifier that allows both half-cycles of the AC waveform to contribute to the

direct current, making it smoother than a half-wave rectifier. A center-tapped rectifier

is preferred to the full bridge rectifier when the output DC current is high and the



output voltage is low. The advantages of using precision rectifier are it will give peak

voltage output as dc; rest of the circuits will give only RMS output.

FILTERS

Pre-filter and post-filter are connected to the regulator IC. Distance between pre-

filter and post-filter should be 5cm. High frequency post-filters are used.

IC VOLTAGE REGULATOR

Voltage regulators comprise a class of widely used ICs. Regulator IC units

contain the circuitry for reference source, comparator amplifier, control device, and

overload protection all in a single IC. IC units provide regulation of either a fixed

positive voltage, a fixed negative voltage, or an adjustably set voltage. The regulators

can be selected for operation with load currents from hundreds of milliamperes to tens of

amperes, corresponding to power ratings from milli watts to tens of watts.

A fixed three terminal voltage regulator has an unregulated dc input voltage, Vi,

applied to one input terminal, a regulated dc output voltage, Vo, from a second terminal,

with the third terminal connected to ground.

The series 78 regulators provide fixed positive regulated voltages from 5 to 24

volts.

For ICs, microcontroller, LCD ---------- 5volts.

For relay circuits ------------ 12volts.



MICRONTROLLER

PIN DIAGRAM



THE MAJOR FEATURES OF PIC 16F873A MICROCONTROLLER

High-Performance RISC CPU:

• Only 35 single-word instructions to learn.

• All single-cycle instructions except for program branches, which are two-cycle.

• Operating speed: DC – 20 MHz clock input.



DC – 200 ns instruction cycle.

• Up to 8K x 14 words of Flash Program Memory,

Up to 368 x 8 bytes of Data Memory (RAM),

Up to 256 x 8 bytes of EEPROM Data Memory.

• Pinout compatible to other 28-pin or 40/44-pin PIC16FXXX microcontrollers.

Peripheral Features:

• Timer0: 8-bit timer/counter with 8-bit prescaler.

• Timer1: 16-bit timer/counter with prescaler can be incremented during Sleep via

external crystal/clock.

• Timer2: 8-bit timer/counter with 8-bit period register, prescaler and postscaler.

• Two Capture, Compare, PWM modules.

- Capture is 16-bit, maximum resolution is 12.5 ns.

- Compare is 16-bit, maximum resolution is 200 ns.

- PWM maximum resolution is 10-bit.

• Synchronous Serial Port (SSP) with SPI™ (Master mode) and I2C™ (Master/Slave).

• Universal Synchronous Asynchronous Receiver Transmitter (USART/SCI) with 9-bit

address detection.

• Parallel Slave Port (PSP) – 8 bits wide with external RD, WR and CS controls (40/44-

pin only).

• Brown-out detection circuitry for Brown-out Reset (BOR).

Analog Features:

• 10-bit, up to 8-channel Analog-to-Digital Converter (A/D).

• Brown-out Reset (BOR).

• Analog Comparator module with:

- Two analog comparators

- Programmable on-chip voltage reference (VREF) module.

- Programmable input multiplexing from device inputs and internal voltage reference.

- Comparator outputs are externally accessible.



Special Microcontroller Features:

• 100,000 erase/write cycle Enhanced Flash program memory typical.

• 1,000,000 erase/write cycle Data EEPROM memory typical.

• Data EEPROM Retention > 40 years

• Self-reprogrammable under software control

• In-Circuit Serial Programming™ (ICSP™) via two pins.

• Single-supply 5V In-Circuit Serial Programming

• Watchdog Timer (WDT) with its own on-chip RC oscillator for reliable operation.

• Programmable code protection.

• Power saving Sleep mode.

• Selectable oscillator options.

• In-Circuit Debug (ICD) via two pins.

CMOS Technology:

• Low-power, high-speed Flash/EEPROM technology.

• Fully static design.

• Wide operating voltage range (2.0V to 5.5V).

• Commercial and Industrial temperature ranges.

• Low-power consumption.



MICROCONTROLLER CIRCUIT

o MICROCONTROLLER

o RESET CIRCUIT

o OSCILLATOR



EXPLANATION: The microcontroller circuit is connected with reset circuit, crystal oscillator, LCD

circuit; the reset circuit is the one which is an external interrupt which is designed to reset

the program. And the crystal oscillator circuit is the one used to generate the pulses to

the microcontroller and it also called as the heart of the microcontroller.

The Liquid Crystal Display which is used to display the what we need the LCD

has fourteen pins in which three pins for the command and eight pins for the data. If the

data is given to LCD it is write command which is configured by the programmer

otherwise it is read command in which data read to microcontroller the data pins are

given to the port 0 and command pins are given to the port 2.

Other than these pins a one pin configured for the contrast of the LCD. Thus the

microcontroller circuit works.

o MICROCONTROLLER

A microcontroller is a complete microprocessor built on a single IC.

Microcontrollers were developed to meet a need for microprocessors to be put

into low cost products.

To solve the problem in microprocessor system is implemented with a single chip

microcontroller. This could be called microcomputer, as all the major part are in

the IC. Most frequently they are called microcontroller because they are used to

perform control functions.

The microcontroller contains full implementation of a standard

MICROPROCESSOR, ROM, RAM, I/O, CLOCK, TIMERS, and also SERIAL

PORTS. Microcontroller also called “system on a chip” or “single chip

microprocessor system” or “computer on a chip”.

Another term to describe a microcontroller is embedded controller, because the

microcontroller and its supports circuits are often built into or embedded in the

devices they control.



ADVANTAGES:

o If a system is developed with a microprocessor, the designer has to go for external

memory such as RAM, ROM or EPROM and peripherals and hence the size of

the PCB will be large enough to hold all the required peripherals. But, the

microcontroller has got all these on a single chip so development of a similar

system with a microcontroller reduces PCB size and cost of the design.

o One of the major differences between a microcontroller and microprocessor is

that a controller often deals with bits, not bytes as in the real world application.

o It has only 35 instructions, so it is easy to learn.

o Design complexity is small.

o It has eight level stacks. And also addresses are in vectored form (pre-defined).



APPLICATIONS:

A microcontroller is a kind of miniature computer that you can find in all kinds of

Gizmos. Some examples of common, every-day products that have microcontrollers are

built in. if it has buttons and a digital display, chances are it also has a programmable

microcontroller brain.

Microcontrollers are designed for use in sophisticated real time applications such as

1. Industrial Control

2. Instrumentation and

3. Intelligent computer peripherals

They are used in industrial applications to control

Motor

Robotics

Discrete and continuous process control

In missile guidance and control

In medical instrumentation

Oscilloscopes

Telecommunication

Automobiles

For scanning a keyboard

Driving an LCD

For frequency measurements

Period measurements

Machinery

Aerospace designs

And other high tech devices



ARCHITECTURE OF PIC 16F873A

o RESET CIRCUIT



The reset circuitry consist capacitor in series with 10K resistor. When switch on

the supply the capacitor is changed and discharged gives high low pulse.

When power is turned on the circuit holds the RST pin high for an amount of time

that depends on the capacitor value and the rate at which it charges.

To ensure a valid reset, the RST pin must be held high long enough to allow the

oscillator to start up plus two machine cycles. On power up, Vcc should rise

within approximately 10ms. The oscillator start-up time depends on the oscillator

frequency. For a 10 MHz crystal, the startup time is typically 1ms. Within the

given circuit, reducing Vcc quickly to zero causes the RST pin voltage to

momentarily fall below zero volt. However, this voltage is internally limited and

will not harm the device.

o OSCILLATOR

Crystal oscillator is the one used to generate the pulses to the microcontroller and

it is also called as the heart of microcontroller. Here we have used 4 MHz crystal

which generates pulses. It offers the highest precision (exactness/accuracy) and

stability. Even the microcontroller has an internal RC oscillator with a maximum

frequency of 4 MHz, noise affect it easily. Because of increasing of aging of

oscillator, resonant frequency varies and cannot get the fixed frequency. So we use

crystal oscillator externally for accuracy.

WHY PIC?



Microchip provides solutions for the entire performance range of 8-bit, 16-bit, and 32-bit

microcontrollers, with a powerful architecture, flexible memory technologies,

comprehensive easy-to-use development tools, complete technical documentation and

post design-in support through a global sales and distribution network. Benefits realized

by selecting Microchip’s microcontroller solutions are:

● Easy migration across product families

● Low-risk product development & faster time to market

● Lower total system cost

● 24/7 support and Regional Training Centers worldwide

● Production programming services

● Certified quality

● Convenient ordering using microchip DIRECT

.

WHY PID ?



1) PID Explained:

Only very control of temperature can be achieved by causing heater power to be

simply switched on and off according to an under or over temperature condition

respectively.

Ultimately, the heater power will be regulated to achieve a desired system temperature

but refinement can be employed to enhance the control accuracy.

Such refinement is available in the form of proportional (P), integral (I), and derivative

(D) functions applied to the control loop. These functions, referred to as control “terms”

can be used in combination according to system requirements. The desired temperature is

usually referred to as the set-point (SP).

To achieve optimum temperature control whether using on-off, P, PD or PID

techniques, ensure that:

a) Adequate heater power is available (ideally control will be achieved with 50% power

applied!)

b) The temperature sensor, be it thermocouple or PRT, is located within reasonable

“thermal” distance of the heaters such that it will respond to changes in heater

temperature but will be representative of the load temperature (the “thing” being heated).

c) Adequate “thermal mass” in the system to minimize its sensitivity to varying load or

ambient conditions.

d) Good thermal transfer between heaters and load.

e) The controller temperature range and sensor type are suitable – try to choose a range

that results in a mid-scale set-point.

Control functions simply described:

a) On – Off – Usually simplest and cheapest but control may be oscillatory. Best

confined to alarm functions only or when “thermostatic” type control is all that is

required, but this may be the most suitable means of control in some applications.



b) Proportional (P) – A form of anticipatory action which slows the temperature rise

when approaching set-point. Variations are more smoothly corrected but an offset will

occur (between set and achieved temperatures) as conditions very.

Average heater power over a period of time is regulated and applied power is

proportional to the error between sensor temperature and set-point (usually by time

proportioning relay switching). The region over which power is thus varied is called the

Proportional Band (PB) it is usually defined as a percentage of full scale.

Offset is the deviation of the sensor temperature from the desired value (set-point).

This can be adjusted out manually by means of a potentiometer adjustment (Manual

reset) or automatically (Integral Action).

c) Proportional + Derivative (PD) – The Derivative term when combined with

proportional action improves control by sensing changes and correcting for them quickly.

The proportional is effectively intensified (its gain is increased) to achieve a quicker

response.

PD action is commonly employed in general applications. Its use can help to minimize or

even eliminate overshoot on system start up, especially when an approach (overshoot

inhibition) feature is incorporated.

d) Proportional + Integral + Derivative (PID)

Adding an integral term to PD control can provide automatic and continuous elimination

of any offset. Integral action operates in the steady state condition by shifting the

Proportional Band upscale or downscale until the system temperature and set-point

coincide.

e) Choosing P, PD or PID

Although superior control can be achieved in many cases with PID control action, values

of the PID terms inappropriate to the application can cause problems.

If an adequately powered system with good thermal response exists and the best possible

control accuracy is required, full PID control is recommended.



If somewhat less critical precision is demanded, the simpler PD action will suffice and

will suit a board range of applications.

If simple control is all that is required, for instance to improve upon thermostatic

switching, Proportional (P) or on-off action will suffice.

Adjustable PID Values?

If the controller specified offers adjustable PID values, the opportunity exists to optimize

or “tune” the control loop to achieve the best possible accuracy in each case.

Various tuning methods exist but the following technique provides a simple approach.

2) Optimizing Control Terms (Tuning):

Fast Tune PID Control

Firstly adjust P to minimum, D to off and I to off (or some very large value if not to off).

Full power is applied to the heaters and is switched off when the measured temperature

rises to set-point. The resultant overshoots T0 and the time taken to attain the maximum

overshoot t0 (mins), allow suitable P, I and D values to be calculated.

These or similar values should then be set on the controller and good result will be

achieved.

For critical processes there are alternative more precise methods for obtaining optimum

PID values. Such methods are more time consuming and Auto Tune

Techniques described below provide an attractive solution in most applications, simple or

complex.



Auto Tune PID Control

Auto tune controllers utilize PID terms and an “approach” feature which are all

optimized automatically. During the first process warm-up the controller familiarizes

itself with the system dynamics and performs self-optimization. No user adjustments are

required for PID values. Some instruments include an “approach” feature to minimize or

eliminate start-up overshoot, also automatically.

3) Control Outputs:

Accurate and reliable energy regulations are essential for good control loop performance

if it is assumed that suitable PID values have been determined and applied.

Depending on the method of applying energy to the process, for example electrical

energy to a resistive heating element, a suitable type of controller output arrangement

must be specified. In some cases, more than one output may be required (e.g. for

multizone heaters, heating-cooling applications).



TEMPERATURE SENSOR

The LM35 series are precision integrated-circuit temperature sensors, whose

output voltage is linearly proportional to the Celsius (Centigrade) temperature. The

LM35 thus has an advantage over linear temperature sensors calibrated in ° Kelvin, as

the user is not required to subtract a large constant voltage from its output to obtain

convenient Centigrade scaling. The LM35 does not require any external calibration or

trimming to provide typical accuracies of ±1⁄4°C at room temperature and ±3⁄4°C over a

full −55 to +150°C temperature range. Low cost is assured by trimming and calibration at

the wafer level. The LM35’s low output impedance, linear output, and precise inherent

calibration make interfacing to readout or control circuitry especially easy. It can be used

with single power supplies, or with plus and minus supplies. As it draws only 60 μA

from its supply, it has very low self-heating, less than 0.1°C in still air. The LM35 is

rated to operate over a −55° to +150°C temperature range, while the LM35C is rated for

a −40° to +110°C range (−10° with improved accuracy). The LM35 series is available

packaged in hermetic TO-46 transistor packages, while the LM35C, LM35CA, and

LM35D are also available in the plastic TO-92 transistor package. The LM35D is also

available in an 8-lead surface mount small outline package and a plastic TO-220

package.





FEATURES OF LM35

Calibrated directly in ° Celsius (Centigrade)

Linear + 10.0 mV/°C scale factor

0.5°C accuracy guaranteeable (at +25°C)

Rated for full −55° to +150°C range

Suitable for remote applications

Low cost due to wafer-level trimming

Operates from 4 to 30 volts

Less than 60 μA current drain

Low self-heating, 0.08°C in still air

Nonlinearity only ±1⁄4°C typical

Low impedance output, 0.1 W for 1 mA load

The output voltage is converted to temperature by a simple conversion factor.



LIQUID CRYSTAL DISPLAY

LIQUID CRYSTAL DISPLAY (LCDs) has materials, which combines the properties of

both liquids and crystals. Rather than having a melting point, they have a temperature

range within which the molecules are almost as mobile as they would be in a liquid, but

are grouped together in an ordered form similar to a crystal.

An LCD consists of two glass panels, with the liquid crystal material sandwiched in

between them. The LCDs are lightweight with only a few millimeters thickness. Since

the LCDs consume less power, they are compatible with low power electronic circuits

and can be powered for long durations.

The LCD does not generate light and so light is needed to read the display. By using

backlighting, reading is possible in the dark. The LCDs have long life and a wide

operating temperature range.

The LCDs have long life and a wide operating temperature range.



Changing the display size or the layout size is relatively simple which makes the LCDs

more customer’s friendly.

The LCDs used exclusively in watches, calculators and measuring instruments are the

simple seven segment displays, having a limited amount of numeric data. The recent

advances in technology have resulted in better legibility, more information displaying

capability and a wider temperature range. These have resulted in the LCDs being

extensively used in telecommunications and entertainment electronics. The LCDs have

been started replacing the cathode ray tube (CRTs) used for the display of text and

graphics and also in small TV applications.



PCB DESIGNING

Printed circuit boards sometimes abbreviated PCB. A flat board made of non-conducting

material, such as plastics or fiber glass on which chips and other electronic components

are mounded usually in pre-drilled holes designed to hold them.

The components on a PCB or more specifically the holes that hold them are connected

electrically by pre-defined conductive metal pathways that are printed on the surface of

the board. The metal leads protruding from the electronic components are soldered to the

conductive metal pathways to form a connection. A PCB should be held by the edges

and protected from dirt and static electricity to avoid damage.

PCB forms the core of electronic equipment domestic and industrial. Some of the areas

where PCBs are intensively used are computers, process control, telecommunication and

instrumentation.

The manufacturing process consists of two methods; print and etch, and plate and

etch.

The software used in our project to obtain;

The schematic layout is PROTEUS 7 PROFESSIONAL.

The software for stimulating is ISIS 7 PROFESSIONAL.

The software for wiring on PCB board is ARES 7 PROFESSIONAL.

STEPS IN DESIGNING:

i. PENALIZATION

ii. DRILLING

iii. PLATING

iv. ETCHING

v. SOLDER MASK

vi. HOT AIR LEVELING



PCB LAYOUT



FIRMWARE IMPLEMENTATION

/*

* Author : PROJECT TEAM

* File : PID.c

* Year : 2010

* Overview : Temperature PID Controller means to control the temperature in

a fixed range, which is achieved with the help of a fan/cooler as

well as a heater. User can Set the required level by using three

switches namely UP, DOWN and SET.

*/

#include <pic.h>

#include "lcd.h"

#include "delay.h"

#include <stdio.h>

_CONFIG(WDTDIS & HS);

#define SW_SET RB0

#define SW_UP RB1

#define SW_DN RB2

#define RLY_HEATER RB6

#define RLY_FAN RB7

#define ON 1

#define OFF 0

#define TRUE 1



#define FALSE 0

#define TOLERENCE 5 // Allowable Temp. Range SET_POINT +/

TOLERENCE

int SET_POINT = 40; // Default Set Point 40 Degree Celcius

bit SET; // Flag to indicate the Status of settings

char msg[16] = "0\0";

unsigned int read_adc(void)

{

ADGO = 1;

while(ADGO);

return((ADRES);

}

// temp = (5/256)*adcval/10mv

// ~ (5*adcval*1000)/(256*10)

// ~ adcval*2

unsigned int get_temp(void)

{

return(2*read_adc());

}

void main(void)

{

char i;

unsigned int temp = 0;



TRISA = 0XFF;

TRISB = 0X07;

TRISC = 0X00;

ADCON0 = 0XC1;

ADCON1 = 0X00;

RLY_HEATER = OFF;

RLY_FAN = OFF;

lcd_init();

lcd_puts("TEMP PID CONTRLR");

lcd_Secline(0);

lcd_puts(" CAS KOTTAYI ");

//10 sec delay

for(i = 0; i < 4; i++)

DelayMs(250);

while(1)

{

lcd_goto(0);

temp = get_temp();

sprintf(msg,"C.T: %2u S.P: %2u ",temp,SET_POINT);

lcd_puts(msg);

lcd_Secline(0);

if(temp <= (SET_POINT - TOLERENCE))

{

RLY_HEATER = ON;

RLY_FAN = OFF;



lcd_puts("HEATER ON,FAN OF");

}

else if(temp >= (SET_POINT + TOLERENCE))

{

RLY_HEATER = OFF;

RLY_FAN = ON;

lcd_puts("HEATER OF,FAN ON");

}

else

{

RLY_HEATER = OFF;

RLY_FAN = OFF;

lcd_puts("HEATER OF,FAN OF");

}

for(i = 0; i < 10; i++)

{

if(!SW_SET)

{ // Set Key Pressed

while(!SW_SET); // Wait for Key Release

SET = FALSE; // Ready to Enter into Settings

while(SET == FALSE)

{

lcd_clear();

sprintf(msg,"S.P:%2u",SET_POINT);

lcd_puts(msg);

while(SW_SET && SW_UP && SW_DN);// wait for a key depression

if(!SW_SET) // Set Key Pressed

{

while(!SW_SET); // Wait for Key Release

SET = TRUE; // Settings Over



DelayMs(250); // Wait a while

}

else if(!SW_UP) // Up Key Pressed

{

while(!SW_UP); // Wait for Key Release

SET_POINT = SET_POINT + 2; // Increment Set Point by 2

}

else if(!SW_DN) // Down Key Pressed

{

while(!SW_DN); // Wait for Key Release

SET_POINT = SET_POINT - 2; // Decrement Set Point by 2

}

}

}

else

DelayMs(10);

}

}

}



CONCLUSION

We are pleasure to conclude our project on the topic “Temperature PID Controller”.

The detail of this project has been made by members of our team sincerely with the

inspiration of out tutors.

Through this project we have done, sensing and maintaining the temperature using IC

LM35, which is very sensitive. This IC is ideal for interfacing with microcontroller

PIC16F873A.

According to the program installed in the PIC, it regulates or works the relays based on

the comparison of current temperature with set point. And the working of the system can

be observed in the LCD.



FUTURE SCOPE

Now-a-days also these types of circuits can be used in large farms and in certain places

where we want to measure the current temperature and also to maintain the temperature

constant according to the user’s decision.

We can use in a wide variety of applications like:

Poultry farm

Industries

Thermal furnace

Boiler

Medical applications

And in all temperature controlling areas



BIBLIOGRAPHY

Electronics For You (EFI) – www.efy.com

www.microchip.com

www.mikroe.com

www.datasheetcatalog.com


http://www.datasheetcatalog.com/

http://www.mikroe.com/

http://www.microchip.com/

http://www.efy.com/

Documents

Project Report- PID