Electric fan automatic control circuit

Frame circuit) bistable circuit. Each bistable circuit controls the level of the output terminal by a single
key . When the circuit is instantly connected to the mains power, the mains power is stepped down by R13, cl,
full-wave rectification of VD, VD2, secondary voltage stabilization of ZD, ZDz, and then electronically filtered by VTs
to obtain a DC voltage of 8.5 V. Because of capacitance C. , C3, C, the voltage at both ends cannot
change suddenly, so the input terminals 1, 5, and 11 of the IC are low level, and the output terminals 2, 6, and 10 of the corresponding inverter
are high level, so each The output terminals 4, 8, and
12 of the bistable circuit are low level. Therefore, the bases of transistors VT,, VT2, and VT4 are at high level, and
VT,, VT,, and VT4 are cut off, and the base of VT3 is at low level , and VT3 is turned on. Because VT4 is cut off, there is no collector current
in VT3 . Therefore, the thyristors vs,, VS2, and VS3 are cut off without trigger current , the lighting lamp L does not light up, and the motor M does not rotate. At the same time, the capacitors C2, C4 and C6 are charged through the resistor scale, R4 and Rg, and can be charged to the power supply voltage of 8.5 V in about 0.18.