As a result the circuit is operating functionly.....
Some review for circuit operation.
During day time, the internal rechargeable 12 Volt SLA battery receives charging current from the connected solar panel through polarity protection diode IN5820 and current limiting resistor R10. If ambient light is normal, transistor T1 is reverse biased by IC1 (LM555). Here IC1 is wired as a medium current inverting line driver, switched by an encapsulated light detector (10mm LDR). Multi-turn variable resistor 1K sets the detection sensitivity. When ambient light dims, transistor BD 678 turns on to drive the super bright LED. The LDR act as a photocell sensor at night. Now this lamp load at the output of T1 energizes. When the ambient light level restores, circuit returns to its idle state and light(s) switched off by the circuit.
