The traditional "220V Cooling Fan" is the use of a fan bearing temperature probes to detect nearby fan inlet temperature, and thus the fan speed can be adjusted. This thermostat solves some problems, but there is rough precision, speed and temperature control can do high-speed low polar shift. PWM pulse width modulation circuit is short, and in industrial control, single-chip "220V Cooling Fan" on the already widely used. And he and motherboards Intel CPU temperature detection combined, will be applied to precisely control the radiator fan speed, and achieved good results. PWM intelligent "220V Cooling Fan" of features First, PWM fan to adjust the fan speed is to get the temperature information directly from the CPU, the fan without any temperature measuring device.