asslam o alikum
well what would be the functionality of this system
what i have understood is that you want that when ever a person is in room lights would be on and else they would be off
there are many sensors that can be used e.g u can count the number of people who enter or leave the room and when entered = left you can switch off the lights
this would be done through either micro controller of simple gate level implemention of digital logic ICs the sensor woud be either IR or the simple LDR used with a light source
another thimg would be that you can make a clap circuit which would switch light on and off on claps simple circuit requires one mic and some transistors
one more way is that you can make an automatic light control system which would change the intensity of light with respect to sroundings for that you would need light intensity sensors but light dependent resistance works fine too
i hope you have got some help
asslam o alikum