Help for a beginner with sensors

Hi, I'm a final year Product design student and am currently doing my final major project. I am attempting to prototype an interaction. This interaction is simple, but not for me. All I need is when it senses you in the room an led will begin to pulse and as you get closer it become a continous light. What materials do I need? And any help with the programming would be alot of help. Thanks Sam

Specifications? Number of targets? Range?

That is actually quite a complex project - and sensing the person is going to be the hard part (and what do you do with multiple people in the room?). A simple PIR "motion sensor" would not work very well (and if the person is either well insulated (heavy coat etc.) or the same temperature as the room, they become basically invisible. RF detectors can detect motion, but I don't think they can resolve location/distance. I almost think the best solution is a wide angle video camera overhead and you process the image (which is well outside the ability of an Arduino unless the subject is a slug ... ). You could break it up into zones with pressure switch mats. Another option would be to track the target from two different locations and calculate their position from where the "beams" cross (do a Google search on soloshot I think it is called).

How about ultrasonic? There's a handy library for coding, and various models of sensor around like the HC-SR04.

Then simple enough to blink an led at a rate which depends on the distance, using an "if/else".

Ultrasonic is not great for human targets, who often, inconvenigently, wear sound-absorbing clothing.