Light controlled lighting controlled by relay

The 220V alternating current is stepped down by the transformer T, bridge rectified by the diode VDI-VD4 and filtered by the capacitor CI, and
a DC voltage of about 12V is output for use by the entire circuit. The light control circuit is composed of components such as VTI, RG, Rl and RP. During the day, the photoresistor
RG is exposed to light and shows low resistance. The transistor VT is turned on, and its collector outputs a low level. The relay controls the transistor
VT2 to be in a cut-off state, and the relay It does not operate when power is lost, its normally open contact is open, and the lighting fixtures controlled by it do not work. At night
, the photoresistor RG shows high resistance without light exposure. The base potential of VT1 decreases and cuts off. Its collector outputs
a high level . VT2 changes from the original cut-off state to the conducting state, and the relay K is electrically closed. , its normally open contact is closed, and
the power supply of the lighting fixture can be turned on to make the lighting fixture light up.
    Changing the resistance of RP can change the base potential of transistor VT1, so it can be used to adjust the light control sensitivity of the circuit.