Street light control circuit 6

This circuit has anti-flash and light-shielding interference capabilities. The contactor of the street light is controlled by relay KA
(not shown in the figure).
    When the shading time during the day does not exceed 7s, due to the charging delay effect of capacitor C2, the potential of point B has not reached 3.2V
, the circuit will not flip, and relay KA is still in the pull-in state. At night, when the strong light interference time does not exceed 1.3s, the potential
of point B will not drop below 1V, so UB-UA is still greater than 0.7V, VTz is still on, VT3 is still off, KA remains released, and the street lights are still on. It will not be extinguished due to interference from strong light.