Ok thanks I will keep it in mind until I got everything soldered up!
Maybe someone want to check this for the last time, to be sure I buy the right stuff:
-Transistor+22kOhms resistor should be fine right? Datasheet transistor: http://www.produktinfo.conrad.com/datenblaetter/150000-174999/163350-da-01-en-Transistor_2N3904.pdf
-LED+220 ohms @15mA GREEN. Datasheet LED: http://www.produktinfo.conrad.com/datenblaetter/175000-199999/184705-da-01-en-WU_8_56_GD_LED_5mm_gruen.pdf
Thanks 