What you need to know about the motor and drive types

In the previous section, I explained a high-level overview of how stepper motors are driven. But it’s more complicated than just hooking things up. There are different types of drives, motors and wiring schemas.

Bipolar and unipolar motors
Broadly speaking, there are 2 types of stepper motors – bipolar and unipolar. The difference is how coils inside the motor are wired up and how they can be energized to get correct magnetic poles for each step. It all boils down to a simple question. How many wires does a stepper motor have? Based on wires which come out of motor we can determine what kind of motor it is and what kind of drive we need to run it.

A 4-wire step motor can be only driven by the bipolar drive. 5-wire motor can only be driven by the unipolar drive since center taps are tied together internally. Motors with 6 and 8 wires can be used with both drive types since you can decide how to hook them up externally.

The difference is how coils inside motors are energized. In the bipolar motor current (polarity) must be reversed in wires for each step. Unipolar motors achieve pole reversal trough center taps in coils, but only energizing half of the coil same time. Adafruit has a good article about unipolar vs bipolar motor coils and wiring. It’s definitely a plus if you make yourself familiar with how they differ.

Driver types
Other than being unipolar and bipolar drives- there are also different ways how they control current and voltage in the motor windings. Primary types are the following:

constant voltage drives also referred to as L/R drives
constant current drives also referred as chopper drives
I don’t go into detail about unipolar drives or constant voltage drives since most likely you end up with a constant current driver with a bipolar motor. Chopper drives are the most popular these days because of the torque and speed limitations of L/R stepper drives.

Chopper drive benefits
When using a chopper drive, the nominal voltage of the motor is mostly irrelevant for practical purposes. At least for hobby user and Arduino enthusiast. So don’t get scared away from stepper motor based on very low rated voltage. The important figure is the rated current.

A chopper drive can run the stepper motor with much higher voltage than the motor’s rated voltage. Higher voltage allows the current to flow through the stepper motor faster, which gives the ability to turn it faster with more torque. Drive keeps current in the motor below the fixed value which keeps motor burning out. Additionally- higher voltage means less heat.

Fixed current is usually set by trimmer pot on the drive board. That allows you to change maximum current based on needed torque and rated current by motor specs.

https://article-realm.com/article/Writing-and-Speaking/Article-Writing/3754-How-to-choose-the-NEMA-23-or-the-NEMA-34-stepper-motors.html
http://www.stepperchina.com/2019/11/22/do-you-really-whichi-is-fit-for-you-nema-17-or-nema23/