Tiny Cooling Fan transform ideas

There are many on the market with PWM function "Tiny Cooling Fan", this type of fan through the motherboard Bioses the fan speed settings to set the fan speed, but this type of chassis fan is not cheap. In addition, there is a class that comes with the thermal resistance of the chassis fan, without going through the motherboard Bioses setup and support, you can adjust the fan speed, but the second class fan is not common. Since not all fans have a temperature control function, to ensure the cooling while keeping fan noise to an acceptable range, we might pass the deceleration line, grafting "Tiny Cooling Fan" input voltage, the governor and other measures to achieve purposes. But these are not easily let us save more carefully adjust the fan speed, and if you need to deal with different environments, manual speed seems a bit of trouble, what shall we do it? If we can all cooling fans have become thermostat "Tiny Cooling Fan" That will save a lot of costs to purchase additional PWM fan.