I plan to have a thermistor attached to a CPU heatsink control the speed of a computer case fan.
For temperatures below 30c (room temp) I want to stop the fan, and for temperatures at or above 60c, I want the fan to run at full.
I've heard someone tell me it's better to use PWM to control the speed since I won't be dissipating so much heat, but it feels silly to use a whole arduino to control a computer case fan. So unless you try to convince me that's a better approach, what I would like is to scale the response of the thermistor to a range of resistances that more closely approximates what the fan needs to reach those goals.
I know I can add to the resistance of a black box with a resistor in series, but I don't know how to scale the output resistance of the termistor. (note: I'm leaning towards this one)
(PS - this is an educational hobby project; I know I could get a simpler premade solution off the shelf)
(PPS - I'd be open to using the 3-pin "fan 2" output from my motherboard (asrock A75M mini-itx), which is already controlled by a temperature, but I don't know how to apply the pinouts to a simple DC case fan)