I have a 12v 55 kg electromagnet. Two wires. I want to run it off a 110 V converter with an on off switch. Further, I want to rheostat the strength with a simple dial or a up/ down button. Lastly, I want to be able to run it on a variable timer I set, i.e. cycles once every five to fifteen seconds and for it to stay on five to fifteen seconds as I need again with a knob or up/down button. List the part numbers, inexpensive but reliable