Servo motors are a type of electromechanical actuators that do not rotate continuously like DC/AC or stepper motors, rather they used to position and hold some object. They are used where continuous rotation is not required so they are not used to drive wheels (unless a servo is modified). In contrast they are used where something is needed to move to particular position and then stopped and hold there.
Servo motors are so called “closed feedback” systems. This means that motor comes with control circuit, which senses if motor mechanism is in desired location and if not it continuously corrects an error until motor reaches proper point.
There are many ways to drive small current motors, those requiring 500mA or less but the L293H Quadruple Half-H driver is a versatile chip that was designed for use with motors, can very easily be controlled with a micro-controller. Using this chip we can drive either 2 DC motors or one Stepper motor and we will learn how to do both in this tutorial.
A stepper motor is a motor controlled by a series of electromagnetic coils. The center shaft has a series of magnets mounted on it, and the coils surrounding the shaft are alternately given current or not, creating magnetic fields which repulse or attract the magnets on the shaft, causing the motor to rotate.