Stepper motor 05/28/16
“Is it possible to have a motor that can make discrete revolutions?”
Like almost any engineering problem that does not violates the laws of physics, the answer is yes. A stepper motor is a motor whose revolutions are divided in to steps (hence the name stepper motor). Stepper motors are made up of an electromagnetic rotor and are surrounded by electrical windings. As each winding is activated with current, the rotor rotates to align itself with the stepper motor (as a result of being magnetized).
There are several different ways to control a stepper motor. The first one is known as a wave drive or a single-coil excitation. As the name implies, each coil is activated one at a time, so the rotation is completely discrete. The next is known as a full drive in which two coils are active at a given time, with a “leapfrog” like pattern of coil activation (one the coil behind the leading one goes off, the coil in front goes on). A half step mode is like a full step except for the fact that there is a delay with each step, so at some time intervals there will be periods in which only one coil is activated. The most common method is called microstepping in which electric current is delivered sinusoidally to each coil so it becomes a continuous change instead of a discrete one.
There are three different types of builds for stepper motors. The Permanent magnet stepper motor uses a permanent magnet as the rotor which uses basic electromagnetism to guide each step. The variable reluctant stepper motor Used a non-magnetized soft iron rotor, and when each winding is activated the rotor rotates so that each of the teeth have a minimum gap between the ends of the magnet. The hybrid-synchronus stepper motor is a combination of the above two stepper motors, Which uses two teethed permanent magnet rotors of opposite polarity.