This circuit lights an electric bulb in darkness. Sensitivity can be controlled using R4. Schematic for gschem.

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Schematic

Schematic

Parts

R1 Photoresistor LDR03 (0.1kΩ-2kΩ lit, 1MΩ-100MΩ dark)
R22.2kΩ
R3220Ω
R4Potentiometer, 10kΩ
R5680Ω
Q1BC547B
Q2BC368
U1 74L14 (Schmitt trigger)
T1..2 Terminals for electric bulb, 6V/2.4W