Lighting switch automatic circuit

The NE555 time base circuit and the AC solid state relay SSR can form an automatic lighting switch circuit. The circuit is as shown in the figure. It can be seen from the figure
that the incandescent lamp EL automatically goes out during the day due to the decrease in the resistance of the photoresistor in the circuit, and at night. EL lights up automatically.
    In the picture. RG is the photoresistor 2CU2B. When RG is exposed to light, the resistance becomes smaller, and the voltage applied to the ② and ⑥ pins of the NE555 time base circuit
is higher, so the NE555 output terminal ③ is low level, the AC solid state relay SSR is cut off, and the Zhaomeng light does not light up.
    When night falls, the RG resistance increases, and the ② and ⑥ voltages of NE555 are lower than 5v. Make the output pin @ change to high level, and
the ① pin of the AC solid-state relay SSR obtains positive power and conducts, making its AC output controlled terminals ③ and ④ conduct. When the incandescent lamp EL lights up, adjusting the potentiometer RP can
change the switching time of the lighting lamp .