If you buy these
You can remove those jumpers (or at least the ENA one) and control the motor speed using a PWM signal from an analog pin
using an analogWrite(ENA, 200); statement. Attached is one of many L298 motor driver sketches I found on the internet that illustrates how to do that. Most of them were written for robots so to turn left, one motor is turned off while the other is left on.
The IN1,1N2 IN3,IN4 control the outputs of the H-BRIDGE. If you look at your schematic,
http://arduino-info.wikispaces.com/file/view/MotorDriver2.jpg/219771672/MotorDriver2.jpg
one motor is connected to OUT1 & OUT2,
and the other to OUT3 & OUT4. so the only way to turn ON motor-1 is to turn OFF OUT2 , while leaving OUT1 ON. Reverse the logic of IN1,IN2 and the motor changes direction. Applying a PWM signal on the ENA or ENB pin results in speed controlled by the duty cycle (0 to 255) of the analogWrite .
The discrete H-Bridge schematic using the logic gates illustrates how the L298 controls direction . Picture a current path going
down through the upper left mosfet , across through the motor and down through the lower right mosfet as one direction and down through the upper right mosfet across (right to left) through the motor and down through the lower left mosfet as the opposite direction. The speed control is accomplished by gating the motor that controls the path to ground for both of the lower motors.
L298_MOTOR_DRIVER_2.ino (1.59 KB)
