Now is the era of energy conservation and environmental protection in the global energy increasingly tense occasion, to ease the pressure brought about by economic development, energy, the country is to promote universal access to energy-saving products. Energy saving product features increasingly become the first factor, the previous "Exhaust Fan" can only control switch, and no exhaust timing and intermittent function, through which the exhaust gas after the logic circuit design product, just by a button you can control the timing of intermittent exhaust time and variable duty cycle to achieve the exhaust product of humanity. At home and abroad, "Exhaust Fan" function has been very complete, but my poor design or not meaningful. Because the logic circuit design and analysis of ideas worth learning and research. And because of its simple and easy to design. No specific material design requirements, making "Exhaust Fan" control logic circuit design of this topic is widely used in the electronic class-based.