L293D Motor Driver Shield Description:

L293D Motor Driver Shield About

Multi-Motor Driver Shield (2-L293D) – Four H-Bridges: Two L293D Motor driver chips – L293D is rated at 0.6A per bridge (1.2A peak) with thermal shutdown protection, internal kickback protection diodes. – Motor Voltages from 4.5VDC to 16VDC. (up to 36V if C6 and C7 are upgrade) – Up to 4 bi-directional DC motors with individual 8-bit speed selection (256 speeds) – Up to 2 stepper motors (unipolar or bipolar) – Pull down resistors keep motors disabled during power-up – Separate Logic and Motor power connections – Terminal block connectors for motors and power – 2 connections for 5V ‘ servos en.wikipedia.org  

A H-bridge is an electronic circuit that switches the polarity of a voltage apply to a load. These circuits are often use in robotics and other applications to allow DC motors to run forwards or backwards. The name is derive from its common schematic diagram representation, with four switching elements configure as the branches of a letter “H” and the load connected as the cross-bar.

Most DC-to-AC converters (power inverters), most AC/AC converters, the DC-to-DC push–pull converter, isolated DC-to-DC converter, most motor controllers, and many other kinds of power electronics use H bridges. In particular, a bipolar stepper motor is almost always driven by a motor controller containing two H bridges.