I think it will be very interesting in my thought that your room light is controlled automatically when a person enters or out from the room.After thinking about it i am presenting a very interesting but useful circuit for saving your electricity.The circuit is about controlling your room electrical equipments.
The main object of this circuit is that when a person enters in your room, all the lights of the room will glow automatically and after just going out from the room all the lights will switched off automatically.Is not it interesting?The principle of this circuit is to use a light sensor.The light sensor senses person and control the light or electrical equipments through the designed circuit.But here is a problem that what should be happen here when two persons enters together in the room i mean one after the other?Because the circuit is designed in such a way that when one person comes to the room it gets one pulse and take required actions on the light means switch on or off.
Now when two persons comes into the room it gets two pulse and the lights remain off becasue in first pulse it gets on but after second pulse it again gets off.In this circuit a very small memory is used which solves our above problem and enables it to taking desired action as our project. The remaining description about the circuit you can read in the manual given below. Download it .