speed control Temperature DC fan mini project

Here is a simple circuit based on two transistors that can be used to control the speed of a 12 V DC fan depending on the temperature.A thermistor (R1) is used to sense the temperature.
When the temperature increases the base current of Q1 (BC 547) increases which in turn decreases the collector voltage of the same transistor. Since the collector of Q1 is coupled to the base of Q2 (BD 140), the decrease in collector voltage of Q1 forward biases the Q2 more and so do the speed of the motor. Also, the brightness of the LED will be proportional to the speed of the motor.
Circuit diagram with Parts list:



Notes.
    The R1 can be a 15K @ 20°C ,N.T.C  thermistor.
    The M1 can be a 12V,700mA fan motor.
    The capacitor C1 must be rated 25V.
    The circuit can be powered from a 12V PP3 battery or 12V DC power supply.
    Assemble the circuit on a good quality PCB or common board.

8 comments :

lets rock said...

what is the use and its applications

satyam rai said...

how can i make it
components required

yogesh said...

what about using a 10k thermister??

Unknown said...

please say the advantage and disadvaantages.

Current Affairs said...

FOr More :

www.trendyprojects.blogspot.com

Anonymous said...

Here are some more mini - projects for free:
www.myclassbook.wordpress.com

Unknown said...

Want to Know more About EEE and Arduino Projects :
Visit:

www.ieeexplorer.blogspot.in

Anonymous said...

pls give me more info regarding this ...

Post a Comment

Followers