The circuit utilizes a voltage comparator and a monostable clock to give the cautioning caution on distinguishing a moving individual. Ic ua741 (Ic1) is utilized as a voltage comparator with two potential dividers in its upsetting and noninverting inputs. Resistors R1 and R2 give half-supply voltage of 4.5 volts to its transforming include (pin 2). Ldr1 and preset Vr1 structure an alternate potential divider to furnish a variable voltage include to the non-upsetting enter (stick 3).
In the event that Vr1 is fittingly balanced for the obliged light level, the yield of Ic1 will be high, which drives pnp transistor T1 out of conduction. This is because of the high potential at the base of T1. The emitter voltage of T1 will be high in this condition, which hinders Ic2 from wavering and Led1 from lighting. Ic2 is wired as a monostable clock. R6 and C2 give a preset time delay.