fan cycling speed control circuit

Published:2011/5/23 20:09:00 Author:John | Keyword: fan | From:SeekIC

The circuit is shown in Figure 1a. NE555 in the circuit is connected as a square wave generator with an adjustable duty cycle. It can change the duty cycle through adjusting RW. When the pin 3 of the NE555 outputs in high power level, primary end of the zero-off-type optocoupler MOC3061 achieves forward current of about 10mA. And it leads the internal infrared emitting diode of gallium silicide to emit infrared light. The two-way switch in photosensitive zero-crossing detector opens when the electricity over zero. Then the power supply of the fan motor is connected. And the fan runs for air supply. When the pin 3 in the NE555 outputs in low power level, two-way switch turns off and the fan stops.



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