A Motor driver shield for Arduino boards that can control up to 4 bi-directional DC motors with individual 8-bit speed selection, or 2 stepper motors (unipolar or bipolar) with single coil, double coil, interleaved or micro-stepping. 2 connections for 5V 'hobby' servos connected to the Arduino's high-resolution dedicated timer - no jitter!
The shield contains two L293D motor drivers and one 74HC595 shift register. The shift register expands 3 pins of the Arduino to 8 pins to control the direction for the motor drivers. The output enable of the L293D is directly connected to PWM outputs of the Arduino.
To increase the maximum current, the L293D allows extra chips with "piggyback". Piggyback is soldering one or two or three extra L293D drivers on top of the L293D drivers on the board to increase the maximum current. The L293D allows parallel operation.
Power for the motors can be supplied from the Arduino boards DC Jack (normally 9V) or from the 2-pin EXT-PWR terminal block.
If you are supplying power from the EXT_PWR terminal block you should remove the PWR jumper or you could damage the shield and the Arduino board.