After the circuit switches off the light from the led will no longer reach the ldr which will cause the circuit to switch the led on again. The circuit will carry on oscillating like this until there is enough ambient light or the light from the led is prevented from reaching the ldr.

Automatic Solar Garden Lights With Leds
Automatic on off light switch circuit. Keep the led away from the ldr. In this article we are going to build a smart automatic onoff switch using arduino which can turn on or off gadgets automatically by sensing the presence of human nearby through the concept of ultrasonic. The light automatically turns on when the bathroom door is opened and remains lit in the occupied state. When the door is opened again the lamp turns off after a very short delay. Circuit diagram for auto switch off light construction and working here the 230 volt 60w bulb is connected through 1 amps bridge rectifier and triac component to the main power supply the gate terminal of triac. This automatic circuit saves energy and greatly assists your visitors especially at night.
There are several ways to make the automatic onoff switching circuit for the inverter but to make it simple and universal is slightly challenging. To make a universal circuit a transformer a regulator a relay and a few discrete components are required. 1 shows the circuit of the home made auto onoff switch. We are going to use ultrasonic module and arduino to sense the presence of human which activates the gadgets such as table lamp or table fan. Here is a simple and low cost automatic bathroom light circuit. If the light from the led is bright enough and it reaches the ldr then the circuit will switch off because there will be enough light reaching the ldr.
The auto switch off light circuit drives ac lamp up to few seconds and turn off the lamp this can be used in staircase or some other application where the few second lighting needed.