I need a way to detect a person walking through a hallway. It is for a lighting project and I only have access to one side of the hall for components. What kind of sensor would be the cheapest to install? The hall is about 3 feet wide and I just need to know when a person is in a 1 or 2 foot section of the hall. I don't want a device that makes any noise or uses visible light. How well would bouncing infrared off the opposite semi gloss painted wall and look for the signal to go away to be the trigger work? Anyone try something like this? Any ideas would be greatly appreciated.
By the way it will be connected to a microcontroller that has an analog input (incase this increases my options).