Help with a project, plz

Hi,
I am trying to build a circuit with a thermally controlled fan with a battery power supply. Any idea on how i should approuch this? And i have seen soom schematics with a resistor with a arrow going into it, could anyone explain what this it and how it works. I have attach a picture of the resistor thingey.
Thanks

1. What kind of fan? (do you have a specific kind picked out yet? like a motor with a propeller on it, or a computer fan)

2. What kind of temperature sensor do you want to use (what type of environment temperature range, physical setup are you working with).

The symbol is a variable resistor. The arrow is supposed to slide up and down the resistive element placing more or less resistance between the two contacts.

Hi not really that sure on which type of fan to get i thought the case fans would be best but not sure? The Temperature sensor would be measuring the temerature around it. So it would make the fans speed up or down.
Thks

http://www.catb.org/~esr/faqs/smart-questions.html

This link will help you out. Maybe you could even help yourself.