hi i saw this http://www.heatsink-guide.com/conten...=control.shtml made 1 it runs 2 pc fans ie the hotter it gets the faster they spin i thought i'd share it with you if its a repost sorry

Done it already..
But good site for people who would like to use this method

Found this very helpful and a cheap alternative to thermostats
i modfied it and instead of conectin it to a pc fan i wired it to a relay that powers a bigger inline fan

I'd up the max voltage if I were you.. What voltage is that sensor rated up to? Most 12V fans run really nicely at 18-24V..

i have no idea how many volts it could take i just use it as above and no probs with temp at all so i have'nt tried it

I just mentioned that the schematic will only drive up to 12V, but yea dc fans are fine to overpower, the caps in them are often rated for 50V I've noticed.. If the sensor can handle higher voltage, you could just hook it up to a higher supply.. If its touchy, just add a resistor..