A Simple White LED Lamp to give light in Corridor or Staircase during night. It saves energy considerably since Zero watt (Not Zero but 15 watts) or CFL (minimum 5 watts) is usually used in such places. The White LED lamp automatically turns on when the ambient light reduces below the set level. It can give sufficient light in a confined area. The circuit is provided to familiarize the working of AND gate IC 7407.
As you know, LDR offers high resistance in dark and low resistance in light. So during day time, LDR conducts and T1 will be forward biased and conducts. So its collector voltage remains low. This keeps IC1 off and LED remain off. When the light falling on the LDR decreases, its resistance increases and T1 turns off. The gate of IC1 now turns high and since it is a NAND gate, output also turns high and LED lights. This condition will be retained till morning.VR1 adjusts the sensitivity of LDR at the particular light level. Power can be obtained from a 6 volt adapter.