Automatic fan controller based on room temperature

Automatic fan controller based on room temperature

1. AUTOMATIC FAN CONTROLLER BASED ON ROOM TEMPERATURE Prepared by P NIKHIL KUMAR REDDY ECE

2. CIRCUIT DIAGRAM

3. KIT

4. IC 741 Thermistor Bridge rectifier Increase in temperature Power supply (230V) 230 V AC BLOCK DIAGRAM

5. Objectives BRIDGE RECTFIER IC 7812 THERMISTER RESISTORS & VARIABLE RESISTOR CAPACITOR IC 741 TRANSISTOR DIODE (2222N ) RELAY(12V) DPDT

6. I ntroduction 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.

7. 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.

8. 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

9. 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 :- NTC – Negative temperature co-efficient PTC - Positive temperature co-efficient

10. 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.

11. 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

12. 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.

13. 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.

14. 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.

15. 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.

16. 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.

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