"Mini Air Cooling Fan" using zero-crossing triac trigger mode, controlled by the microcontroller triac-off, by changing each control cycle on and turn-off thyristor AC complete full-wave signal number to adjust the load power, and thus achieve the purpose of speed control. Because "Mini Air Cooling Fan" INT0 signal reflects frequency voltage zero crossing time, so as long as the external interrupt 0 interrupt service routine complete control of the door opening and closing, and the use of frequency control interrupt service to count and determine the amount of n, ie Each interrupt once performed for n minus 1 count, if n is not equal to 0, maintain control level "1" and continue to open the "Mini Air Cooling Fan" control gate; if n = 0, then the control level is reset to " 0 ", close the control gates, to SCR zero trigger pulse no longer pass.