1. "Waterproof Cooling Fan" series with an internal motor temperature resistance, when the temperature rises or decreases, temperature resistance with temperature change, and then make a series of micro-fan motor is saying (ie stator ) resistance to change, the fan speed will change. Also can have temperature control IC, higher precision of this design some similar principles
2. PWM function with "Waterproof Cooling Fan", when the ambient temperature changes, the temperature will affect the products that do have a PWM design to the motherboard, the motherboard will send a message to the fans, so that changing the PWM duty cycle, miniature fan will vary the duty ratio, the rotational speed changes linearly
3. An external temperature control switch, such as when the temperature reaches 40 degrees, the temperature control switch is closed, "Waterproof Cooling Fan" is energized to work, less than 40 degrees, the thermostat switches off the fan power to stop work, which volume switch is about the size of a thumb, temperature sensitivity is poor.