temperature controlled fan system

temperature controlled fan system:

in this temperature controlled system used in many we use this system for fan controlling is based on we use 12V dc supply.and we use two transistor.first one is BC 547,second one is BD 140.we use 7 resistor(1.5k,270 ohm,22k,680 ohm,470 ohm,1k,2k) and one capacitor(100 microF) and one LED,one fan.this is the main component for the temperature controlled fan system.


in this process we have use only 12 V DC supply. the positive terminal of the DC supply is connected with two resistor(1k,2k) and emitter terminal of pnp transistor(BD 140).the 2k resistor is connected with base terminal of the npn transistor and 1.5k resistor.the collector terminal of the npn transistor is connected with 1k resistor and base terminal of the pnp transistor.the collector terminal of the pnp transistor is connected with fan and 22k and 680 ohm and capacitor.the emitter terminal of the npn transistor is connected with 270 ohm resistor.the 680 ohm resistor is connected wirh 470 ohm resistor and LED.and the resistor(1.5k,270 ohm,470 ohm),fan, capacitor and LED another terminal is connected with negative terminal of the power this process is temperature controlled fan system.

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