Make This Automatic LED Staircase Light

The Automatic LED Staircase Light circuit operates as a discrete timing and amplification system powered by a 9V battery or power adapter. At the heart of the system are complementary bipolar junction transistors—specifically the NPN BC547 (T1) and the PNP BC557 (T2)—which work together to form a solid-state switching network. When an operator triggers one of the push switches (S1 or S2), a small base current is introduced to the transistor network, causing the active transistor pair to transition from a cutoff state into saturation. This rapid state change completes the current path from the 9V power source through the current-limiting resistors (such as R1, R2, and R3) to illuminate the 5mm white LEDs (LED1 and LED2) positioned at either end of the staircase. To achieve the automatic shut-off feature, the circuit incorporates capacitive networks using components like capacitor C1. When the switch is released, C1 slowly discharges through the associated biasing resistors, maintaining the transistor base voltage for a predetermined duration of a couple of minutes. Once the capacitor voltage drops below the base-emitter conduction threshold, the transistors return to cutoff, cleanly cutting power to the LEDs without requiring any programmable microcontroller or software.