DC Brushless Motor - Built-in Thermistor control - Questions

[rfdes]

Hi
I have zero  experience with Brushless DC fans and how they are built.  I have a DC PC fan with a extra pair of wires which allows connection to a thermistor for controlling the speed of the fan.  I would like to make use of this fan for a project and want to know whether there is a typical schematic that explains the method used to control the fan's speed.  Are most of these fans similar in topology where a somewhat universal schematic exists?  My search efforts have not been fruitful, so if someone has any pointers as to the method of speed control operation, it would be appreciated.

Thanks

[strawberry]

some have PWM speed control input, some have tachometer output ... need datasheet of particular fan

[rfdes]

Thanks for the response.
The part number of the fan is DFB802512H made by Younglin Tech.  All of the datasheets that I found only show a 2 wire version.  The one I have is a 4 wire version.  1 red/1 black/2 yellow.
The 2 yellow are for a 2 wire thermistor.  There is no PWM input or Tachometer output on this model.
I've been unable to find any schematics, etc.

[strawberry]

to get thermistor slope and estimate shematic components. take thermistor and measure resistance at room temperature for first point then put in fridge with thermometer and then measure resistance for second point.. can skip and do try and error method and add adjustment pots for trimming
use 555 timer to generate PWM or just comparator to turn on/off fan at specific tempeature and power MOSFET to switch fan power on or off

or code mcu