Hello guys, I'm having some trouble with a electronic project that my professor gave to me.
The objective of the project is to create a circuit to turn on a cooler (fan 80mm).
The especifications are that we need to use a bipolar junction transistor as a temperature sensor, when a warm object ( ex: soldering iron) is approached, the circuit must trigger the cooler. The ideia is to vary the hfe of the transistor to use him in the cut reagion.

I was trying to make this with a relay, and using the BJT saturation region.

Sorry for bad english, isnt my native language.
Hope you guys can help me.

 

Lets see schematic.

 

Hint:

Vbe also goes down with temperature.

 

Firstly, here are some guidelines to posting on forums.

Use a subject title that is more useful than "Please, can you guys help?"
Something like "Temperature controller circuit" would be better.

Show a schematic of what you are attempting to create.

All school assignments should begin by showing your efforts.