Thanks for all experts here.

I want to ask Michael Karas that how can you draw this schematic? Is the software you used a freeware or shareware? In addition, can you explain how the circuit works in detail? I just knew that the darlington pair can enlarge the overall current gain by multipling both individual current gains, right? Also, followed the Ohm's Law that:

5V / ( Dropping resistor + Winding resistance ) = rated current of each winding

As the rated current = 1.5A,
then Dropping resistor + Winding resistance = 5 / 1.5 = 3 Ohms?

It is very small too. May I try larger resistance, say 20 Ohms, but I will try if it is applicable. May I apply the white rectangular resistor (I don't know the exact name) on my circuit?