Sensing darkness and LED light in the room with battery backup and available for Rs 390/-, the Automatic Night Lamp Cum Emergency Light uses a light-dependent resistor (LDR) as the sunlight sensor  and a total of 9 high-brightness white LEDs. Separate resistors are connected in series with each row of the LEDs.
The working of the circuit is very simple. During daytime, light falls on the LDR1 and it offers a low resistance. As a result, both the transistors (T1 and T2) do not conduct and the LEDs (D1 through D9) do not glow. On the other hand, during nighttime, the light does not fall on LDR1 and it offers a high resistance. As a result, transistors T1 and T2 conduct and the LEDs (D1 through D9) glow.
Assemble the circuit on a PCB and enclose in a cabinet. Connect the LEDs (D1 through LEDD9) and LDR1 on top of the box and place the unit such that during daytime the sunlight falls directly on LDR1. For powering the circuit, use a 9V battery & 9-0-9V/500mA transformer. The power supply rectifier diode D11 & D12 & filter capacitor C2 is already in the circuit.VR1 for adjusting the light intensity for LDR.

Sensing darkness and LED light in the room with battery backup and available for Rs 390/-, the Automatic Night Lamp Cum Emergency Light uses a light-dependent resistor (LDR) as the sunlight sensor  and a total of 9 high-brightness white LEDs. Separate resistors are connected in series with each row of the LEDs.
The working of the circuit is very simple. During daytime, light falls on the LDR1 and it offers a low resistance. As a result, both the transistors (T1 and T2) do not conduct and the LEDs (D1 through D9) do not glow. On the other hand, during nighttime, the light does not fall on LDR1 and it offers a high resistance. As a result, transistors T1 and T2 conduct and the LEDs (D1 through D9) glow.
Assemble the circuit on a PCB and enclose in a cabinet. Connect the LEDs (D1 through LEDD9) and LDR1 on top of the box and place the unit such that during daytime the sunlight falls directly on LDR1. For powering the circuit, use a 9V battery & 9-0-9V/500mA transformer. The power supply rectifier diode D11 & D12 & filter capacitor C2 is already in the circuit.VR1 for adjusting the light intensity for LDR.