AUTOMATIC FAN CONTROLLER BASED ON ROOM TEMPERATURE

Prepared byP NIKHIL KUMAR REDDY

ECE

CIRCUIT DIAGRAM

KIT

IC 741Thermistor

Bridge rectifier

Increase in temperature

Power supply(230V)

230 VAC

BLOCK DIAGRAM

OBJECTIVES

• BRIDGE RECTFIER

• IC 7812

• THERMISTER

• RESISTORS & VARIABLE RESISTOR

• CAPACITOR

• IC 741

• TRANSISTOR

• DIODE (2222N)

• RELAY(12V) DPDT

INTRODUCTION• This automatic fan controller is used to monitor the temperature of the load without any human interruption by

using temperature depends upon thermistor. Generally fan speed is controlled manually. it is done by normal

regulator circuit which is controlled outside manually. In this project if the temperature increase a certain limit.

Then a fan is automatically switched on to bring the temperature to normal state.

• The automatic fan controller circuit uses a thermistor along with an operational amplifier is used for monitoring

the input voltages. The thermistor  temperature sensor  is used to detect the temperature. If the temperature

exceeds the predefined limit, then the thermistor will give a signal to operational amplifier to activate the lamp

using a relay to retain the temperature at that value.

BRIDGE RECTIFIER

• A Bridge rectifier is an arrangements of four or

more Diodes in a bridge circuit configuration.

which provides same output polarity.

• It is used for converting an alternating current

(AC) Input into a direct current (DC) as output.

IC 7812

• The ic 7812 is also called as voltage regulator has 3 pins in this Input

Ground Output

A voltage regulator is a electronic device. This is designed

It can operate both in AC&DC

THERMISTER

• A thermistor is a type of resistor whose resistance dependent on

temperature . The word is a portmanteau of thermal and resistor.

thermistors are widely used as current limiters.

• Thermistors are differs from resistance temperature detectors.

In this thermistors generally a ceramic (or) polymer material is used.

There are 2 types of thermistors :-

I. NTC – Negative temperature co-efficient

II. PTC - Positive temperature co-efficient

VARIABLE RESISTOR

• A Variable resistor consists of a track which provides the

resistance

path. Two terminals of a device is connected to both

the end of a track. The third terminal is connected to a WIPER

that decides the motion of a track. The motion of track helps the

increase or decrease the resistance.

• A potentiometer has 3 terminals in this two terminals are fixed

and one terminal is movable. Variable resistor is also called as

potentiometer. Potentiometers are operated by rotating shafts.

Potentiometers are commonly used to control electrical devices.

CAPACITOR• An electrical device consisting of two conducting plates

separated by an electrical insulator (the dielectric ), designed

to hold an electric charge.

• Charge builds up when a voltage is applied across the plates,

creating an electric field between them.

• The standard unit of capacitance is the farad. Symbol is “F”.

Three prefixes (multipliers) are used, µ (micro), n (nano) and p (pico): µ means 10-6 (millionth), so 1000000µF = 1F n means 10-9 (thousand-millionth), so 1000nF = 1µF p means 10-12 (million-millionth), so 1000pF = 1nF

TRANSISTOR

• A transistor is a semiconductor device used as amplifier and

switch electronic signals and electrical power.

• A transistor is a basic electrical component that alters the flow of

electrical current.

• If we now join together two individual signal diodes back-to-

back, this will give us two PN-junctions connected together in

series that share a common P or N terminal. The fusion of these

two diodes produces a three layer, two junction, three terminal

device forming the basis of a Bipolar Junction Transistor, or BJT.

DIODE

• In electronics, a diode is a two-terminal device (Thermionic

diodes may also have one or two ancillary terminals for a heater).

• Diodes have two active electrodes between which the signal of

interest may flow, and most are used for their unidirectional

electric current property. The varicap diode is used as an

electrically adjustable capacitor.

RELAY (12V) DPDT

• An electrically operated switch, for example a 9V battery circuit

connected to the coil can switch a 230V AC mains circuit.

NO = Normally Open, COM = Common, NC = Normally Closed.

ADVANTAGES & DISADVANTAGES

• Quick cooling.

• More moisture removable.

• Lower fan noise and quieter operations.

• Good for night time. When cooling loads are low and humidity is high.

ADVANTAGSE:-

DISADVANTAGES:-

• Thermistor is the heart of the circuit , if thermistor is damaged the whole

circuit

well be damaged .

• Speed control is independent of individual preference.

APPLICATIONS

• Applicable to the protection of the power circuits of conversion power supply.

• Applicable for switching power supply, UPS power supply, electric heaters, incandescent

lamps and other lights.

• It is also applicable for A.C’s, kitchen exhausters, ceiling fans.

THANK YOU