I have a Geared DC Motor rated 12V, 0.6A, 180RPM, 3kg.cm, 66% Efficiency. I measured the impedance of the disconnected motor at 45 Ohm. I want to use it with a with a simple 12V 1A DC Power Supply in a Field Current Control Circuit to be able to dial in variable speeds. Will the circuit in the attached diagram work? What are good Theoretical Resistance values to start with for R1 and the Potentiometer to give me a wide range of speeds with no load on the motor? For which Wattage should the Resistor and POT be rated to deal with the currents correctly? Thanks in advance!