An Arduino servo motor with DC motor and potentiometer.
Beware with correct position of wire motor (pin 5 and 6 of Arduino). If they are changed, the motor will turn to the end travel of pot and can broke it. Make a test with a low power (motorPWM variable) first. If you want change the direction of motor, use something like this in Arduino loop: runMotor(1023-val);
Using only proportionality for read/target value.
Using proportionality for read/target value and pwm.