"Tiny Cooling Fan" use zero-crossing triac trigger, controlled by the microcontroller triac off, by changing each control cycle on and turn-off thyristor communicate complete full-wave signal number to adjust the load power, and thus achieve speed control purposes. Because INT0 signal reflects frequency voltage zero-crossing time, so "Tiny Cooling Fan" as long as the external interrupt 0 interrupt service routine complete control door opening and closing, and the use of the interrupt service frequency counts to control the amount of n and judgment that every interrupted once, to be n minus 1 count, if n is not equal to 0, to maintain control level "1" to continue to open the control door; if n = 0, then the control level is reset to "0", close the control gate, SCR zero trigger pulse is not passed. Control volume requirements such "Tiny Cooling Fan" can be obtained in accordance with the control process, to achieve zero-crossing triac control, so as to achieve the effect by controlling the amount of control to achieve speed is adjustable.