This Solar 12V for load 24 Bright 3w LED circuit is an automatic street light using a LDR and 12V/10W solar panel. During day time, the internal rechargeable 12 Volt SLA battery receives charging current from the connected solar panel through polariy protection diode IN5820 and current limiting resistor 15E/10w. If ambient light is normal, transistor BD678 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 trimpot P1 (variable resistor 100k) sets the detection sensitivity. When ambient light dims,transistor BD678 turns on to drive the load Bright LED. Now this lamp load at the output of transistor energises. When the ambient light level restores, circuit returns to its idle state and light(s) switched off by the circuit.
