Automatic Temperature Controlled Fan ..Read more http://electronicsproject.org/automatic-temperature-controlled-fan/

Automatic Temperature Controlled Fan

Power supply Circuit:- The primary AC voltage is step down to 12 – 0 – 12 by using transformer X₁ which further rectified using bridge rectifier (D₁ through D₄). The rectified output is filtered using capacitor and given to input pin 1 of voltage regulator IC 7812 (IC₁). The regulated output is taken from pin 3 of IC₁where pin 2 is grounded.

PARTS LIST

Resistors (all ¼-watt, ± 5% Carbon)

R₁ = 100 KΩ

R₂ = 56 KΩ

R₃ = 39 KΩ

R₄, R₅, R₆ = 1 KΩ

VR₁, VR₂ = 

Capacitors

C₁ = 1000 µF/40V

C₂, C₃ = 1000 µF/25V

C₄ = 0.1 µF

Semiconductors

IC₁ = LM7812 (12V regulator IC)

IC₂ = LM324 (operational amplifier)

T₁, T₂ = SL100

D₁ – D₆ = 1N4001 (rectifier diode)

Miscellaneous

TT₁ = AD590 (temperature transducer)

RL₁, RL₂ = 12V 200Ω

..Read more http://electronicsproject.org/automatic-temperature-controlled-fan/