On the market "Cooling Fan Manufacturer" spin down the line is in the fan series with a 12V input resistance, prolonged use will make it heat, long past will be damaged. Today we teach can make a stepless the "Cooling Fan Manufacturer" governor, look forward DIY spirit. The governor uses the LM317T regulator IC to do at the core of the circuit, in the process of adjustment to control the intensity by LM317T voltage, so that the "Cooling Fan Manufacturer" speed change, without cause overheating rheostat.