Choosing a Motor Controller

Before you can think of how to drive your motor, you need to know what kind of motor/actuator you are using. This is because each motor type got different spec especially on the current consumption, rated voltage and torque.

1. Rated voltage - always check your motor operating voltage. if your motor operates at 12V, you cannot use a motor controller that support output voltage at only 5V or less.
2. Current requirement - Choose a motor controller that offers output current equal to or above the motor’s continuous current consumption under load. If your motor require 3A current under load, it means that you will need at least 4A motor driver to drive the motor. otherwise you might burn your motor controller. What if we don't know the current requirement for the motor?? - try to attach the motor to laboratory power supply that has digital output display for voltage and current. increase the voltage gradually until the motor running and you can see the current consumption from the current display. try to halt the motor while its running and you'll get the current draw under load.
3. Control method is another important consideration. Control methods include analogue voltage, I²C, PWM, R/C, UART (a.k.a. serial). If you are using a microcontroller, check to see which pin types you have available and which motors are viable for you to choose. If your microcontroller has serial communication pins, you can choose a serial motor controller; for PWM, you will likely need one PWM channel per motor.
   
4. The final consideration is a practical one: Single vs. dual (double) motor controller. A dual DC motor controller can control the speed and direction of two DC motors independently and often saves you money (and time). The motors do not need to be identical, though for a mobile robot, the drive motors should be identical in most cases. You need to choose the dual motor controller based on the more powerful DC motor. Note that dual motor controllers tend to have only one power input, so if you want to control one motor at 6V and the other at 12V, it will not be possible. Note that the current rating provided is almost always per channel.
5. examples of motor controller or motor driver can be found here

Power window motor require high operating current(>3A)

reference : http://www.robotshop.com/ Read More!