big led project

hello... so i went back and got a irfz24n mosfet got everything together (im including a pic) and most of it is working w/o a problem 1 little detail is im not able to make the strip turn off completely ive been playing with different basic programs but to no luck as to turn the strip completely off, ive also tried different connections the strip does dim a lot more if i connect the source to led - instead of drain to -....... maybe someone can tell me if im connecting anything wrong ???

thanks for all the help