Arduino motion detection sensor

I have been willing to start playing with electronics for some time, now I have some free time and I have decided to go for it :-) I got Arduino board, bread board, some jumper cables, lots of resistors, and I built my own 1st serial IR receiver for Linux. Currently I am testing the IR motion detection sensor, it depend on detecting the change of the IR in the surrounding area and triggers an alarm, in my case just to light up a small red LED as long as there is motion, and turn it off after 100ms, sorry for the bad quality of the video, enjoy the video which demonstrate the detection of the motion in light and in a dark room :-)