Can you reverse the rotation of a DC motor and control its speed?
The answer is yes. There are three common kinds. Series motors where the field is in series as in a starter motor, shunt motors where the field is in parallel as in a sewing machine, and permanent magnet motors where the field is provided by a magnet. Reverse the motor by reversing the supply to the rotor or the field. Control the speed in shunt or permanent magnet types by keeping the field constant, and varying the supply to the rotor. The field can be controlled, but the result is not quite what is expected. Reducing the field causes the motor to go faster with less torque. Series motors are often controlled by adjusting the supply across the whole motor (rotor and field).
