I'm powering a motor, and instead of rotating at a constant rate, it rotates roughly a third revolution every half second or so; the rotation keeps starting and stopping. There's no load on the motor, but I plan to add a gear pump fixture (en.wikipedia.org/wiki/Hydraulic_pump) onto it. Also, the LED on the wall charger that lights up when the charger is plugged in dims out when I connect the motor.
I have a USB wall charger plugged into an outlet with a USB cable plugged into it. The other end of the USB cable is cut, and the red and black wires are going to the leads of the motor. This diagram demonstrates the setup.
The wall charger is DC 5V 1A supply. The motor is a RS-360SH.
How can I get the motor to rotate at a constant rate?
I measured the amperage that the motor is using, and it was always below 0.5 A. I understand that the motor is drawing amperage from the power supply.
I know that current limiting resistors, other circuits, and PWM are an option, but I'm trying to keep this low cost. Using the formula I = V/R, I get 1A = 5V/R, R = 5 ohms. So my total resistance needs to be 5 ohms or greater to limit at or below the supply amperage of 1A. The resistor would need to dissipate 5W (P=A^2*R, P=1^2*5= 5 watts). I do not have any resistors capable of dissipating 5 watts.
What is the best solution to limit current so that my power supply is protected from burning out?