Stepper Motor tutorial + Arduino & Raspberry Pi implementation

Stepper motors are used in applications where one needs a high precision of rotational accuracy. Applications like 3d printers, CNC, or automation machinery. Unlike traditional brushed and brusless motor these motors have full torque at a stand still postition so they can hold their position

Tearing one apart we can see that these stepper motor use multiple Electromagnets positioned on the stator with a magnetized rotor. (Broll) DC motors are different in that the stator has a permanent magnet not the rotor.

Looking even closer at the rotor, we see these little u-shaped cutouts- these help channel magnetic force (Text for exact name in video) and later we will discuss them in more detail.

Now, unlike most motors, stepper motor’s rotational resolution is rated by steps. That means how many distinct positions can the make per 360 degree rotation. A 200 step motor can make finer movements in increments of 1.8 degrees compared to a 100 step motor that can only move in increments of 3.6 degrees.

We could go one step further and use a technique called microstepping to further increase the resolution of the stepper motors to a crazy high amount but with a torque trade-off.

There are 3 types of stepper motors:
Permanent magnet stepper- these have a magnatized rotor
Variable reluctance stepper- these have a non magnetic rotor but features those u cutouts
Hybrid synchronous stepper which features both u shaped cutouts and a magnetic core.

Now there are 2 types of wiring for stepper motors
Unipolar and bipolar

Unipolar energizes the phases of the motor in the same way. This allows them to be controlled with simple transistors but they have less torque cause only half of the coils can be energized at once. Watch the demo drawing

Bipolar use Hbridge drivers(Talked about in brushed motor video) to alternate the current flow in the phases and turn the motor. Watch the demo drawing

Watch the side by side comparison- In a nutshell, unipolar motors are easier motors to drive but at the cost of twice the wiring in the coils as bipolar motors

Lets do a quick demo using the common nema 14/17 hobby mot used in 3d printers, cnc, and other hobby use cases. It’s a hybrid style motor and we will be wiring it as a bipolar motor and using the common A4988 stepper motor driver to control it.

Wire- animation
Code- Swing from one side to the other, show libraries
Demo

Advantages of Stepper Motor:
The motor has full torque at standstill.
Excellent response to starting, stopping and reversing.
Very reliable since there are no contact brushes in the motor.
A wide range of rotational speeds can be realized as the speed is proportional to the frequency of the input pulses

Cons- heavy, driver

This video barely scratches the surface of stepper motors. Its just to give you a taste

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