Help required with my automation system

[Aniket Maithani]

First of all I would like to thank all the people who attended the first meetup. Secondly, I got some ray of hope that I am not the only software guy who gets boggled by these hardware terms such as SHIELDS, INTERRUPTS etc.
                     Well I want to make a project (hobbyist nature), in which I want to design a system which would detect the presence of people in the room, and will turn the electrical equipment ON and OFF in the room accordingly. My only exposure to hardware was when I created a open power monitor using AVR and Raspberry Pi. So the basic outline of the project is

• Sensor detects the "human presence"
• Sends the signal to a central hub, lets say Raspberry Pi or whatever
• My micro controller/hub will initiate the switching system, and turn on the electrical equipment accordingly.
  

  I want help in two cases, firstly the cheapest sensor I could use (occupancy sensor etc.) and secondly the mechanism that would trigger the whole electrical system ON and OFF.

I hope it's clear what I want to achieve as I don't have enough knowledge about the HARDWARE VOCABULARY. And secondly I want to keep the budget as low as possible, like around 10-15K at max.

[Vikas Patial]

Hi

Such devices are already there , You can search ebay.in for PIR switch , it will switch the light on / off . About Rs 500 + 

If you want to make something it might be a little more complicated -

http://www.instructables.com/id/DIY-Arduino-Motion-Sensor-Lighting-Control/

Regards