Staircase Lighting Control
A simple system using multiple motion sensors and a light sensor to activate stairway lighting at night - and avoid the problem of lights turning out when you're chatting on the landing ;-)
Do you have a large staircase with many floors? This might help you out.
The code is written to be self-explanatory rather than super efficient.
All you need are some cheap components like PIR sensors, a relay and a light sensor and you're off!
The actual components I used were :
Light sensor -
PIR sensors -