Circuit working principle: As can be seen from the figure, the LED is the power and air pressure sensor action indication. After the vacuum cleaner is working for a long time, the internal dust bag will not be cleaned in time to increase the load of the motor. If the internal vacuum pressure reaches or exceeds 21 kPa, the air pressure sensor will operate, and the air pressure sensor will detect the air pressure sensor action, no matter the motor work. In which power state, it will quickly return to the low power state, and the LEDs and LED2 will flash in a cycle of Is and a duty cycle of 50% to remind the user to clean the dust, thus effectively protecting the motor.
220 V AC is divided into two channels after being stepped down by transformer T. One way is connected to the RAz end of the single-chip microcomputer through R8 and C6 for AC zero-cross sampling, so that the thyristor controlled by the single-chip microcomputer can be completely synchronized with the AC mains, and the thyristor phase shift trigger mode is adopted. The high and low voltages are isolated by the optocoupler to improve the safety; the other is connected to the 78L05 through the diode VD.
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