Hello, im going to create a crane, arm device that can pick up metallic objects using a magnet, then with a press of a button, or switch it turns off. i know you need a soft iron core pole thing for the magnet. i also know kinda how to magnetize a piece of iron but in afraid i am thinking along the wrong lines. so how exactly shall i do it. (the magnet part please) also is there a change i would be able to change the strength with a variable resistor or something?? please help.