1

PROBLEM STATEMENT

GBPUAT is an agro-based university with considerable efforts of research being

applied in this field through experimentation; therefore a large part of these studies takes

place in the several polyhouses that are installed across the university campus. To provide

these installations with a low-cost ventilation temperature control system, our project aims to

fulfill this very need.

The project aims to automatically control and regulate the speed of Induction Motor

according to the current temperature of the surroundings thereby increasing the air flow rate

and bringing about a resultant decrease in temperature. It is aimed at designing an integrated

low cost solution that can be easily installed in external environments of

Polyhouses/Greenhouses and to remove the need for manual control of the ventilation

system.

2

Chapter 1: INTRODUCTION

The concept of this project is to create an Automatic Temperature Control System to

control the temperature of a system. The circuit maintains the temperature of the system in a

particular range. The fan RPM increases with increase in temperature and vice versa. For the

circuit, it consists of Temperature Sensing Unit, ATMEGA16 microcontroller, LCD Module,

Switching Device, Driver Circuit and a Fan. It will operate based on the values or ranges of

temperature in the system which is detected by the Temperature Sensor.

The Temperature Sensor detects the temperature of the system. The Temperature

Sensor consists of an LM35 IC. The temperature sensor is connected to the ADC input of the

ATMEGA16 microcontroller. It converts the analog input to a digital value. The

ATMEGA16 generates Pulse Width Modulation (PWM) value according to the temperature

sensor value. The ATMEGA16 is connected to a driver circuitwhich regulates the speed of

the fan. The LCD module is also connected to the ATMEGA16 microcontroller. The LCD

module displays the current temperature and PWM value.

3

Chapter 2: LITERATURE REVIEW

2.1 DC Motor:

A DC motor is a mechanically commutated electric motor powered from direct

current (DC). The stator is stationary in space by definition and therefore its current. The

current in the rotor is switched by the commutator to also be stationary in space. This is how

the relative angle between the stator and rotor magnetic flux is maintained near 90 degrees,

which generates the maximum torque.

DC motors have a rotating armature winding (winding in which a voltage is induced)

but non-rotating armature magnetic field and a static field winding (winding that produce the

main magnetic flux) or permanent magnet. Different connections of the field and armature

winding provide different inherent speed/torque regulation characteristics. The speed of a DC

motor can be controlled by changing the voltage applied to the armature or by changing the

field current. The introduction of variable resistance in the armature circuit or field circuit

allowed speed control. Modern DC motors are often controlled by power electronics systems

called DC drives.

The introduction of DC motors to run machinery eliminated the need for local steam

or internal combustion engines, and line shaft drive systems. DC motors can operate directly

from rechargeable batteries, providing the motive power for the first electric vehicles. Today

DC motors are still found in applications as small as toys and disk drives, or in large sizes to

operate steel rolling mills and paper machines.

The speed of a d.c. motor is given by:

N=(V-IR)/Ф (2.1)

It is clear that there are three main methods of controlling the speed of a d.c. motor, namely:

(i) By varying the flux per pole. This is known as flux control method.

(ii) By varying the resistance in the armature circuit. This is known as armature control

method.

(iii) By varying the applied voltage V. This is known as voltage control method.

4

2.2 Controlling dc motor speed with Pulse Width Modulation (PWM)

PWM is an effective method for adjusting the amount of power delivered to the load.

PWM technique allows smooth speed variation without reducing the starting torque. In PWM

method, operating power to the motors is turned on and off to modulate the current to the

motor. The ratio of on to off time is called as duty cycle. The duty cycle determines the speed

of the motor. The desired speed can be obtained by changing the duty cycle. The Pulse-

Width-Modulation (PWM) in microcontroller is used to control duty cycle of DC motor

drive.

PWM is an entirely different approach to controlling the speed of a DC motor. Power

is supplied to the motor in square wave of constant voltage but varying pulse-width or duty

cycle. Duty cycle refers to the percentage of one cycle during which duty cycle of a

continuous train of pulses. Since the frequency is held constant while the on-off time is

varied, the duty cycle of PWM is determined by the pulse width. Thus the power increases

duty cycle in PWM.

5

2.3 Induction Motor

An AC motor is an electric motor driven by an alternating current (AC).It commonly

consists of two basic parts, an outside stationary stator having coils supplied with alternating

current to produce a rotating magnetic field, and an inside rotor attached to the output shaft

that is given a torque by the rotating field.

An induction or asynchronous motor is an AC motor in which current is induced in

the rotor winding by the magnetic field of the stator winding, by electromagnetic induction.

Therefore they do not require the sliding electric contacts, such as a commutator or slip rings,

which are needed to transfer current to the rotor winding in other types of motor such as

the universal motor. Rotor windings consist of short-circuited loops of conductors and are

made in two types: the wound rotor and the squirrel-cage rotor.

Three-phase squirrel-cage induction motors are widely used in industrial drives

because they are rugged, reliable and economical. Single-phase induction motors are used

extensively for smaller loads, such as household appliances like fans. Although the simple

induction motor is a fixed-speed device, they are increasingly being used with variable-

frequency drive (VFD) systems, which allow the speed to be varied. VFDs offer especially

important energy savings opportunities for existing and prospective induction motors in

variable-torque centrifugal fan, pump and compressor load applications. Squirrel cage

induction motors are very widely used in both fixed-speed and VFD applications.

There are the following methods for the Speed control of the Induction motors:

1.Speed control by Frequency Changing or Variable Frequency control method

2.Speed control by Voltage Variation or Stator voltage Control Method

3.Speed control by pole changing method

6

2.4 Speed Control by Voltage Variation using TRIAC

The Induction motor speed can be controlled by changing the applied voltages on

the stator; because in induction motor the output torque is directly proportional to the square

of the voltage. Thus the motor speed controlled without changing the supply frequency, for

example, if the supply voltage value is decreases to its half, the motor torque is decreases ¼th

times; the torque is directly proportional to the speed of the motor.

In stator voltage control method, the stator voltage is controlled by a SCR; these

SCRs are connected with three phase supply (with each Phase) in anti parallel conduction.

The output voltage of the SCR is controlled by the firing angle of the SCR. Increasing the

firing angle, decreases the output voltage and this way the speed of the induction motor is

decreases. By decreases the firing angle, increasing the output voltages and the speed of the

motor is increases.

7

Chapter 3: PROJECT RESOURCES REQUIRED

3.1 Softwares

3.1.1 Proteus ISIS 7.6: Proteus is the best simulation software for various designs with

microcontroller. It is mainly popular because of availability of almost all microcontrollers

in it.This software combines mixed mode circuit simulation, micro-processor models and

interactive component models to allow the simulation of complete micro-controller based

designs. Proteus provides the means to enter the design in the first place, the architecture

for real time interactive simulation and a system for managing the source and object code

associated with each project. In addition, a number of graph objects can be placed on the

schematic to enable conventional time, frequency and swept variable simulation to be

performed.

3.1.2 ExpressPCB: ExpressPCB is a simple to use PCB layout packager aimed at the

first time user and designer. ExpressPCB offers a schematic capture program that

integrates with their PCB layout software. The schematic and layout files can be linked to

automatically carry changes forward. ExpressPCB is meant to be used with the

ExpressPCB PCB manufacturing service and does not support outputting to standard

formats directly. ExpressPCB offers a file conversion service for a fee if standard outputs

are required.

8

3.2 Hardware

3.2.1 Atmega16 Microcontroller:

Fig 3.1: Pin Diagram of Atmega16 Microcontroller

ATmega16 is an 8-bit high performance microcontroller of Atmel‟s Mega AVR

family with low power consumption. Atmega16 is based on enhanced RISC architecture

with 131 powerful instructions.. Atmega16 can work on a maximum frequency of 16MHz.

ATmega16 has 16 KB programmable flash memory, static RAM of 1 KB and EEPROM

of 512 Bytes. ATmega16 is a 40 pin microcontroller.

There are 32 I/O (input/output) lines which are divided into four 8-bit ports

designated as PORTA, PORTB, PORTC and PORTD. ATmega16 has various in-built

peripherals like USART, ADC, Analog Comparator, SPI, JTAG etc. Each I/O pin has an

alternative task related to in-built peripherals.

9

Advanced Features of Atmega16 Microcontroller:

• Up to 16 MIPS Throughput at 16 MHz

• 16K Bytes of In-System Self-Programmable Flash

• 512 Bytes EEPROM

• 1K Byte Internal SRAM

• 32 Programmable I/O Lines

• In-System Programming by On-chip Boot Program

• 8-channel, 10-bit ADC

• Two 8-bit Timer/Counters with Separate Prescalers and Compare Modes

• One 16-bit Timer/Counter with Separate Prescaler, Compare Mode, and Capture

• Four PWM Channels

• Programmable Serial USART

• Master/Slave SPI Serial Interface

• Byte-oriented Two-wire Serial Interface

• Programmable Watchdog Timer with Separate On-chip Oscillator

• External and Internal Interrupt Sources

10

The following table shows the pin description of ATmega16:

Pin no. Pin name Description Alternate Function

1 (XCK/T0)

PB0

I/O PORTB, Pin 0 T0: Timer0 External Counter Input.

XCK : USART External Clock I/O

2 (T1) PB1 I/O PORTB, Pin 1 T1:Timer1 External Counter Input

3 (INT2/AIN0)

PB2

I/O PORTB, Pin 2 AIN0: Analog Comparator Positive I/P

INT2: External Interrupt 2 Input

4 (OC0/AIN1)

PB3

I/O PORTB, Pin 3 AIN1: Analog Comparator Negative I/P

OC0 : Timer0 Output Compare Match

Output

5 (SS) PB4 I/O PORTB, Pin 4 In System Programmer (ISP)

Serial Peripheral Interface (SPI) 6 (MOSI) PB5 I/O PORTB, Pin 5

7 (MISO) PB6 I/O PORTB, Pin 6

8 (SCK) PB7 I/O PORTB, Pin 7

9 RESET Reset Pin, Active

Low Reset

10 Vcc Vcc = +5V

11 GND GROUND

12 XTAL2 Output to Inverting Oscillator Amplifier

13 XTAL1 Input to Inverting Oscillator Amplifier

14 (RXD) PD0 I/O PORTD, Pin 0

USART Serial Communication Interface 15 (TXD) PD1 I/O PORTD, Pin 1

16 (INT0) PD2 I/O PORTD, Pin 2 External Interrupt INT0

17 (INT1) PD3 I/O PORTD, Pin 3 External Interrupt INT1

18 (OC1B) PD4 I/O PORTD, Pin 4

PWM Channel Outputs 19 (OC1A) PD5 I/O PORTD, Pin 5

20 (ICP) PD6 I/O PORTD, Pin 6 Timer/Counter1 Input Capture Pin

21 PD7 (OC2) I/O PORTD, Pin 7 Timer/Counter2 Output Compare Match

Output

11

22 PC0 (SCL) I/O PORTC, Pin 0

TWI Interface 23 PC1 (SDA) I/O PORTC, Pin 1

24 PC2 (TCK) I/O PORTC, Pin 2

JTAG Interface

25 PC3 (TMS) I/O PORTC, Pin 3

26 PC4 (TDO) I/O PORTC, Pin 4

27 PC5 (TDI) I/O PORTC, Pin 5

28 PC6

(TOSC1)

I/O PORTC, Pin 6 Timer Oscillator Pin 1

29 PC7

(TOSC2)

I/O PORTC, Pin 7 Timer Oscillator Pin 2

30 AVcc Voltage Supply = Vcc for ADC

31 GND GROUND

32 AREF Analog Reference Pin for ADC

33 PA7 (ADC7) I/O PORTA, Pin 7 ADC Channel 7

34 PA6 (ADC6) I/O PORTA, Pin 6 ADC Channel 6

35 PA5 (ADC5) I/O PORTA, Pin 5 ADC Channel 5

36 PA4 (ADC4) I/O PORTA, Pin 4 ADC Channel 4

37 PA3 (ADC3) I/O PORTA, Pin 3 ADC Channel 3

38 PA2 (ADC2) I/O PORTA, Pin 2 ADC Channel 2

39 PA1 (ADC1) I/O PORTA, Pin 1 ADC Channel 1

40 PA0 (ADC0) I/O PORTA, Pin 0 ADC Channel 0

Fig 3.2: Pin Description of Atmega16 Microcontroller

12

3.2.2 Temperature Sensor LM35:

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).

LM35 Pin Diagram:

+Vcc 1

Output 2

GND 3

Fig. 3.3 LM35 Pin Diagram

13

3.2.3 LCD JHD162A

LCD is based on the HD44780 microcontroller (Hitachi) and can display messages in

two lines with 16 characters each. It can display all the letters of alphabet, Greek letters,

punctuation marks, mathematical symbols etc on a miniature liquid crystal display. It is

also possible to display symbols made up by the user. Other useful features include

automatic message shift (left and right), cursor appearance, LED backlight etc.

An LCD (Liquid Crystal Display) basically works on the concept of Light

Polarization of a „Liquid Crystal‟ under the influence of an Electric Field. Every LCD

contains a Back-Light behind the Liquid Crystal array, which acts as a light source.

When an Electric Field is applied across certain fluids, it changes the way they allow

light to pass through them, that is, it changes the orientation of the liquid crystal

molecules as a result they do not allow light to pass through them. Hence, by applying

suitable potential difference, we can control if light passes or doesn‟t pass through the

LCD pixels.

Fig 3.3: Pin Diagram of LCD

14

Pin Description of JHD162A:

LCD Pin Symbol Function External connection

1 Vss Signal Ground (GND) External ground (Power section)

2 Vdd Vcc for LCD Power supply for logic (+5v)

3 Vo Contrast Adjust Externally connected potentiometer

4 RS Register Select Signal To micro-controller control pins

5 R/W Read/Write Select Signal To micro-controller control pins

6 E Enable Signal To micro-controller control pins

7 DB0 Four low oder bidirectional

three-state data bus lines .

These four are not used if 4-

bit interface used.

To micro-controller data pins

8 DB1 To micro-controller data pins

9 DB2 To micro-controller data pins

10 DB3 To micro-controller data pins

11 DB4 Four low oder bidirectional

three-state data bus lines .

These four are not used if 4-

bit interface used

To micro-controller data pins

12 DB5 To micro-controller data pins

13 DB6 To micro-controller data pins

14 DB7 To micro-controller data pins

15 1 LED (K) Back light LED cathode terminal

16 15 LED (A) Back light LED cathode terminal

Fig 3.4: Pin Description of LCD

15

3.2.4 Motor Drive IC L293D

Fig. 3.5: Pin Diagram of L293D

Pin Diagram shows that L293D consists of four inputs (A), which accepts TTL

logic voltage level and four outputs (Y) that gives VCC2 Voltage. That allows L293D

to be used as two "reversible" output or four "one-way" outputs. There are two more

TTL inputs (EN), which stands for enable. This means that pin 1 (1,2EN) enables

outputs 1Y and 2Y. Without pin 1 set to logical 1, the outputs will remain inactive.

The enable inputs are usually hooked to +5V to be set still. In "motor driving"

applications, enable inputs are called slow stop and it's used for speed control.

Switching from logical 1 to logical 0 causes motor to rotate according to the switching

interval.

16

Pin configuration of L293D

Pin no. Function Name

1 Enable pin for motor 1; active high Enable 1,2

2 Input 1 for motor 1 Input 1

3 Output 1 for motor 1 Output 1

4 Ground (0v) Ground

5 Ground (0V) Ground

6 Output 2 for motor 1 Output 2

7 Input 2 for motor 1 Input 2

8 Supply Voltage for motors; 9-

12V(upto 36V)

Vcc 2

9 Enable pin for motor 2; active high Enable 3,4

10 Input 1 for motor 1 Input 3

11 Output 1 for motor 1 Output 3

12 Ground (0V) Ground

13 Ground (0V) Ground

14 Output 2 for motor 1 Output 4

15 Input 2 for motor 1 Input 4

16 Supply voltage; 5V(upto 36V) Vcc1

Fig. 3.6: Pin Configuration of L293D

17

3.2.5 Optocoupler

Fig. 3.7: Pin Diagram of Optocoupler

Optocouplers (MOCs) are used to transmit signals between circuits that do not share a

power source.MOCs have a LED and a sensor inside. If the LED is turned on, it activates

the sensor and lets the current flow.

This circuit is used to isolate signal circuitry from transients generated or transmitted

by power supply and high-current control circuits. An optocoupler, also known as opto-

isolator, is a component that transfers electrical signals between two isolated circuits by

using light. Opto-isolators prevent high voltages from affecting the system receiving the

signal.

18

3.2.6 Power Supply

Fig. 3.8: Circuit Diagram of Power Supply

The ATMEGA16 requires a regulated 5 volt supply voltage. The 7805 voltage

regulator is used to provide for that. The 7805 takes in a voltage between 7 and 30

volts and regulates it down to exactly 5 volts. The first capacitor takes out any ripple

coming from the transformer so that the 7805 is receiving a smooth input voltage, and

the second capacitor acts as a load balancer to ensure consistent output from the 7805.

The 7805 has three leads. If we look at the 7805 from the front (the side with printing

on it), the three leads are, from left to right, input voltage (7 to 30 volts), ground, and

output voltage (5 volts).

19

3.2.7 Triac

A triac is basically a bidirectional electronic switch, which can conduct current in either

directionwhen it is triggered. The triggering can be either a positive or negative voltage

applied to its gateelectrode. By applying a steady state gate signal, the triac may be

triggered into a low impedancestate where conduction across the main terminals will

occur. The gate signal polarity need notfollow the main terminal polarity. Gate

requirement vary depending on the direction of the mainterminal current and the gate

current.

Fig. 3.9: Symbol & Pin Diagram of Triac

Pin 1: Main Terminal 1

Pin 2: Main Terminal 2

Pin 3: Gate

20

3.2.8 Printed Circuit Board

A printed circuit board, or PCB, is used to mechanically support and electrically

connect electronic components using conductive pathways, tracks or signal

traces etched from copper sheets laminated onto a non-conductive substrate. When the

board has only copper tracks and features, and no circuit elements such as capacitors,

resistors or active devices have been manufactured into the actual substrate of the board, it

is more correctly referred to as printed wiring board (PWB) or etched wiring board. Use of

the term PWB or printed wiring board although more accurate and distinct from what

would be known as a true printed circuit board, has generally fallen by the wayside for

many people as the distinction between circuit and wiring has become blurred. Today

printed wiring (circuit) boards are used in virtually all but the simplest commercially

produced electronic devices, and allow fully automated assembly processes that were not

possible or practical in earlier era tag type circuit assembly processes.

21

Chapter 4: METHOD

4.1 Block Diagram:

Fig. 4.1: Block Diagram of Project

22

4.2 Circuit Diagram:

Fig. 4.2: Circuit Diagram of Project

23

4.3 Working:

The circuit maintains the temperature of the system below a particular value. A fan is

used for controlling the temperature of the system. The fan RPM increases with increase in

temperature and vice versa. The current temperature within the greenhouse is measured by

using a temperature sensor. When the current temperature is above the set maximum

temperature, the system is cooled by using a fan. When the current temperature is below the

set maximum temperature, no control action is needed. The current temperature of the room

is continuously displayed on the LCD. This makes user aware of current temperature of the

system.

The Temperature Sensor detects the temperature of the system. The Temperature

Sensor consists of an LM35 IC. The temperature sensor is connected to the ADC input of the

microcontroller. It converts the analog input to a digital value. The microcontroller generates

the corresponding PWM value according to the sensed temperature.

If using AC motor as the load, we use an optocoupler to isolate the 230V circuit from

the microcontroller circuit.The switching device (triac) is connected to the microcontroller

through the optocoupler. The firing angle of triac is changed according to the PWM value of

the microcontroller; hence, changing the speed of the fan.When using DC motor as load, the

PWM generated output control signals are sent to the Motor Driver IC L293D. Motor Driver

IC L293D is fed with the PWM generated output from microcontroller. The speed of the fan

is controlled by the ON time of the PWM generated by the controller. With increasing ON

time, the speed of the fan reduces the temperature of the system. The LCD module is also

connected to the microcontroller. The LCD module displays the currenttemperature and

PWM value in terms of percentage.

24

4.4 Algorithm:

1. Initialize Ports & LCD.

2. Sense temperature.

3. Display temperature on LCD with corresponding PWM.

4. If temperature<28ºC

Then PWM=0

Motor OFF

5. If 28º C<temperature< 38ºC

Then PWM=31

Motor ON and run at low speed

6. If temperature>38º C

Then PWM=98

Motor ON and run at full speed

7. Goto step 2

25

4.5 Program:

#define F_CPU 8000000UL

#include <util/delay.h>

#include <avr/io.h>

#include <string.h>

#include <avr/interrupt.h>

/*Global Variables Declarations*/

/*LCD function declarations */

voidLCD_send_command(unsigned char cmnd);

voidLCD_send_data(unsigned char data);

voidLCD_init();

voidLCD_goto(unsigned char y, unsigned char x);

voidLCD_print(char *string);

void Convert1(unsigned int value);

void Convert(unsigned int value);

voidbin_to_ascii_two(unsigned char);

voidInitPWM();

#define LCD_DATA_PORT PORTC

#define LCD_DATA_DDR DDRC

#define LCD_DATA_PIN PINC

#define LCD_CNTRL_PORT PORTD

#define LCD_CNTRL_DDR DDRD

#define LCD_CNTRL_PIN PIND

#define LCD_RS_PIN6

#define LCD_RW_PIN5

#define LCD_ENABLE_PIN 4

#define FREQ 8000000

#define prescaler 8

unsigned int Count=0;//,d1,d2,d3,d4,x1,x2,x3,x4;

void main(void)

{ unsignedinti,brightness,tempC,display;

DDRC=0xff;

DDRD=0xf0;

26

LCD_init();

InitPWM();

LCD_goto(1,1);

LCD_print("COT PANTNAGAR");

LCD_goto(2,8);

LCD_print("Temp:");

LCD_goto(2,1);

LCD_print("PWM:");

DDRA = 0x00; // Configure PortA as input

while(1)

{

ADCSRA = 0x97; // Enable the ADC and its interrupt feature

// and set the ACD clock pre-scalar to clk/128

ADMUX = 0xE0; // Select internal 2.56V as Vref, left justify

// data registers and select ADC0 as input channel

ADCSRA |= (1<<ADSC);

while(!(ADCSRA & (1<<ADIF)));

tempC = ADCH; // Output ADCH to PortD

LCD_goto(2,13);

itoa(tempC/10,display,10);

LCD_print(display);

itoa(tempC%10,display,10);

LCD_print(display);

LCD_send_data(0xDF);

LCD_print("C");

//bin_to_ascii_two(((brightness*100)/256)+1);

bin_to_ascii_two(((255-brightness)*100)/255);//*100);

if(tempC<=27)// &&tempC<=30)

{

for(brightness=0;brightness<250;brightness++)

{

SetPWMOutput(brightness);

}

27

} if(tempC>=28 &&tempC<=37)

{

for(brightness=0;brightness<175;brightness++)

{

SetPWMOutput(brightness);

}

}

if(tempC>=38) {

for(brightness=0;brightness<5;brightness++) //5

{

SetPWMOutput(brightness);

} }

}

}

/* This function sends a command 'cmnd' to the LCD module*/

voidLCD_send_command(unsigned char cmnd)

{

LCD_DATA_PORT = cmnd;

LCD_CNTRL_PORT &= ~(1<<LCD_RW_PIN);

LCD_CNTRL_PORT &= ~(1<<LCD_RS_PIN);

LCD_CNTRL_PORT |= (1<<LCD_ENABLE_PIN);

_delay_us(2);

LCD_CNTRL_PORT &= ~(1<<LCD_ENABLE_PIN);

_delay_us(100);

}

/* This function sends the data 'data' to the LCD module*/

voidLCD_send_data(unsigned char data)

{

LCD_DATA_PORT = data;

LCD_CNTRL_PORT &= ~(1<<LCD_RW_PIN);

LCD_CNTRL_PORT |= (1<<LCD_RS_PIN);

28

LCD_CNTRL_PORT |= (1<<LCD_ENABLE_PIN);

_delay_us(2);

LCD_CNTRL_PORT &= ~(1<<LCD_ENABLE_PIN);

_delay_us(100);

}

voidLCD_init()

{ LCD_send_command(0x38);

LCD_send_command(0x0C);

LCD_send_command(0x01);

_delay_ms(10);

LCD_send_command(0x06);

}

/* This function moves the cursor the line y column x on the LCD module*/

voidLCD_goto(unsigned char y, unsigned char x)

{

unsigned char firstAddress[] = {0x80,0xC0,0x94,0xD4};

LCD_send_command(firstAddress[y-1] + x-1);

_delay_ms(10);

}

voidLCD_print(char *string)

{

unsigned char i=0;

while(string[i]!=0)

{

LCD_send_data(string[i]);

i++;

}}

voidbin_to_ascii_two(unsigned char binbyte)

{unsigned char adc_out1;

char i=0;

char position=0xC5;

29

for(i=0;i<=1;i++)

{

adc_out1= binbyte %10;

binbyte=binbyte/10;

LCD_send_command(position);

LCD_send_data(48+adc_out1);

_delay_ms(10);

position--;

}

}voidSetPWMOutput(uint8_t duty)

{

OCR2=duty;

}

void Wait()

{

_delay_loop_2(3200);

}voidInitPWM()

{

TCCR2=0x75; //Set OC0 PIN as output. It is PB3 on ATmega16 ATmega32

DDRD|=(1<<PD7);

}

30

4.6 PCB Design:

Fig. 4.3: PCB Circuit Layout

31

Chapter 5: Results

Fig. 5.1: Waveform at 25º C

The results at 25º C(<28 º C) were obtained as given above with PWM=1.

These were matching with those obtained on the model. At this temperature, the fan

was OFF.

32

Fig. 5.2: Waveform at 30º C

The results at 30º C(28 º C< temperature < 38 º C) were obtained as given above with

PWM=31. These were matching with those obtained on the model. At this

temperature, the motor was ON and working at low speed.

33

Fig. 5.3: Waveform at 40º C

The results at 40º C(38 º C< temperature ) were obtained as given above with

PWM=98. These were matching with those obtained on the model. At this

temperature, the motor was ON and working at full speed.

34

Chapter 6: Conclusion

As displayed in the results, the prototype was successful in implementing the aims of

the project. The project model provides with a low-cost automatic temperature control

system.

The project was successful in automatically controlling and regulating the speed of

Induction Motor according to the current temperature of the surroundings thereby

increasing the air flow rate and bringing about a resultant decrease in temperature. It was

aimed at designing an integrated low cost solution that can be easily installed in external

environments of Polyhouses/Greenhouses and to remove the need for manual control of

the ventilation system, which it effectively proves to do.

35

Chapter 7: Future Scope

1. By replacing the temperature sensor with pressure sensor, we can use it in furnaces.

When large quantities of metal enters the furnace, the pressure sensor would sense

the additional weight and would run the furnace at higher output, thereby increasing

efficiency by saving energy in idle stages and reducing running costs.

2. It can be used in various industrial applications such as to control the temperature in

boilers.

3. It can be used in various industrial applications such as to control the temperature in

Refrigerators and Air Conditioners as air flow control component.

4. By replacing the fan with a heater and reversing the programming logic, it can be

used to maintain temperatures in a narrow range in incubation centres and scientific

laboratories.

36

References

Maizidi Ali, MekinlyRolin D &CarseyDenny , “Microcontroller & Embedded

System”, Pearson Education, 2nd Edition.

8051 Microcontroller and Application, 2nd

Edition, Chris Braithwaite, Fred Cowan

and HasanParchizadeh. Prentice Hall Inc. New Delhi India, 2001.

Embedded System, Raj Kamal, 3rd

Edition, Tata McGraw Hill

Electrical Machinery Fundamentals, S. J. Chapman, McGraw Hill, 2005

http://www.datasheetscatalog.com