GOOD MORNING

PROGRESS SEMINAR

TOPIC:-TEMPERATURE CONTROLLED FAN

GROUP MEMBERS:-

Pooja Baruah(94061)

Baishali Chakraborty(94062)

Pinky Deka(94077)

Amrapalee Purkayastha(94081)

Components Required

Components Quantity1. Temperature sensor LM35 1

2. Op-amp LM741 3

3. Opto-coupler MOC3011 1

4. Power triac BT136 1

5. Microcontroller AT89S52 1

6. Microcontroller interfacing devices -

7. Resistors -

8. Capacitors -

9. Diodes -

INTRODUCTION

This Project is used to control the speed of the fan according to the temperature and it also indicates the temperature. The system will get the temperature from the temperature sensor and it will control the speed according to the values stored by the user. The System is fully controlled by the microcontroller AT89S52

CONTROL FLOW CHART

TEMPERATURE SENSOR

RAMP GENRRATOR

COMPARATOR

OUTOCOUPLER DRIVER STAGE

POWER DRIVE CIRCUIT

POWER SUPPLY5V 12V

DETAILED EXPLANATION POWER SUPPLY– The circuit needs a d.c power supply of +5V and -5V for the A/D

converter IC– And a d.c supply of +12V and -12V for the various op-amps used in

the circuit– We used a step down transformer of 220V-12V a.c– The a.c voltage is rectified to d.c by a bridge rectifier circuit– The d.c voltage is then filtered to remove the ripples with the help

of capacitors– This o/p voltage is then fed to 4 ICs

7812 IC to get +12V 7805 IC to get +5V7905 IC to get -5V7912 IC to get -12V

Temperature sensorThe temperature sensor chosen for our circuitis the LM35 ICLM35 IC:-• LM35 is a precision IC temperature sensor with its

output proportional to the temperature (in oC). • With LM35, temperature can be measured more

accurately than with a thermistor.• The operating temperature range is from -55°C to 150°C.• The output voltage varies by 10mV in response to every

oC rise/fall in ambient temperature• Work under any environmental condition.

Pin Diagram

Pin No

Function Name

1 Supply voltage; 5V (+35V to -2V)

Vcc

2 Output voltage (+6V to -1V) Output3 Ground (0V) Ground

The output of the temperature sensor is fed to anon-inverting amplifier to amplify the output For the need of our project we chose our gain ofthe amplifier to be 5 We know for non-inverting amplifierVoltage gain Av=1+R2/R1

Choosing R2=10 k ohm and Av =5

We have,R1=(1/(Av -1))× R2

= 2.2 k ohmHence we take R1=2.2k ohm & R2=10k ohm To achieve a required gain of 5

Ramp generator

We need a ramp waveform which serves as thereference waveform while comparing the outputOf temperature sensor.The ramp generator is built using an op-ampastable multivibrator circuit.

Circuit For Ramp Generator

ComparatorThe function of the comparator is to comparethe output voltage of the sensor stage with thatfrom the ramp generator and produces pulsesthat have varying pulse-width depending on themagnitude of the sensor output voltage.We have used LM741 op-amp as comparator

LM741 as comparator

Outo-coupler stage

There are two functions of the outo-coupler stage:-

• It serves as an isolator between the sensor stage and the power drive stage

• It is used to trigger the power-triac circuit that is present in the power drive circuit.

We are using MOC 3011 as the outo-coupler

MOC 3011

• The MOC3011 is an optically isolated triac driver device.

• These devices contain a GaAs infrared emitting diode and a light activated silicon bilateral switch, which functions like a triac.

• They are designed for interfacing between electronic controls and power triacs to control resistive and inductive loads

Description Of Opto-coupler

•An opto-coupler is used to isolate the low voltage DC , from the high voltage AC•The input opto-coupler is often a light emitting diodes while the output is often a photo triac for switching on a triac

Power drive circuit

Power Triac:-• Allows Biderectional flow of current• Can be triggered by either a positive or a negative current applied to its gate electrode•Once triggered, the device continues to conduct until the current drops below a certain threshold, called the holding current.• Used as AC switches• Controls flow of current in a circuit

BT136

Features:•It is a 3-pin IC•Power TRIAC•Conducts current in both

directions when triggered

through gate•AC switch

Pin Diagram of BT136

Symbol

Operation of BT136

•By varying the firing angle we can control the flow of current through the Triac•Firing angle here refers to the pulse with of the comparator output

Operating principleThe operation is thus-When the temperature is fixed, by the gain ofthe amplifier the comparator would generateregular pulses to sustain the temperaturethrough the fan. Then if the temperature increases ,the comparatorwould end up generating wider pulses which inturn results in increased firing angle and henceincreases the fan speed.

USE OF MICROCONTROLLER

The main role of the microcontroller AT89S52 used in our project is to:-• Read temperature from the temperature sensor• Display the temperature on a 16×2 LCD connected to it.• Take decision to operate the fan attached to it when temperature changes.

AT89S52:-

Features• It is a 8-bit microcontroller• 8K Bytes of In-System Programmable Flash Memory • 4.0V to 5.5V Operating Range • Operating speed- 0 Hz to 33 MHz • 256 x 8-bit Internal RAM• 32 Programmable I/O Lines• Three 16-bit Timer/Counters • Eight Interrupt Sources • Full Duplex UART Serial Channel

Pin Diagram:

Our Progress:-

• Till date we have made the power supply, the ramp generator and the comparator.

• Our next approach will be the temperature sensor .

ConclusionIt is a very useful circuit as-• It simplifies life when used for household

purpose.• It can be used inside electronic devices to cool

it that generate heat.• The same principle can be used in sensible Air

conditioner

Reference

• www.atmel.com• www.bristolwatch.com/ele/triac2.html• www.elprojects.blogspot.in• Op-Amps And Linear Intregated Circuits

-Ramakant.A.Gayakwad