Temperature Controlled Fan

29 March 2016 User Review

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Depending upon the temperature the speed of the fan is regulated. In power supply unit 7805 voltage regulator is used to regulate 9v into 5v. Capacitors 100uf are used to stabilize the voltage. Pow_LED1 is used to indicate power on condition. In this project, we are using a temperature sensor LM35 for reading the temperature. There will be an amplifier section for amplifying the temperature voltage. This amplified voltage is given to the base of a Darlington pair IC for regulating the speed of the fan.

The resistor value used in the amplifier section is R4= 220ohm and R3 = 120ohm. Here we use LM358 opamp IC for the amplifier circuit. When the temperature varies, the output voltage of the LM35 changes and this voltage is amplified by the amplifier circuit. The amplifier circuit is done using LM 358. The output from this amplifier is given to Transistor T3 TIP 122. In the initial stage T3 will be in off state and once output from amplifier comes to the base of the transistor it will be turned on, thus speed of fan is regulated. So when the temperature increases, the output voltage changes and the fan speed is regulated.

Circuit Diagram

circuit diagram

PCBKIT

 

Component List:

 

PARTS LIST

SEMICONDUCTORS

IC1

IC2

T3

POW_LED

 

-7805  Voltage Regulator

-LM 358

-TIP 122 NPN Transistor

- 3mm Led Red

RESISTORS ( all ¼  -watt)

R3

R4

R6

R5

 

-120 ohm

-220 ohm

-330 ohm

-1 k

CAPACITORS

C3,C4

 

-100µF,25V electrolytic

MISCELLANEOUS

BATTERY1

TEMP SENSOR

FAN

IC BASE

 

-9V  Battery with  Strip

-LM35 temperature sensor

-9V DC Fan

-8 pin

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