Machine movements are generally made either by pneumatic valves or by electro-magnetic motors. Omitting the pneumatics for now, the electro-magnetic motors generally further divide to alternating-current or AC in short and direct-current, or DC in short. So far so good.

Anyway, AC motors are high power, heavy-duty devices. Heavy things are hard to get moving and have high inertia once they are already set in motion, meaning they do not really like to change their movement too much. This means AC motors have little place in delicate little movements you are probably interested in here. This leaves us with the DC motors group.

A humble DC motor

Now the taxonomy gets a little trickier, and I just want to get to one specific motor type as you may already picked up from the title. Most prominent players here are permanent magnet brushed DC motors, which are in fact the ones that are usually called simply DC motors because not only they use DC current, the direction of their rotation is determined by the direction of the current that passes through it. Pass the current through it and it rotates. Simple as that, this is a rare property regarding motors.

Then there are the brush-less DC motors, or BLDC in short to easily differentiate between the two, as they quite different inside. Remember, there are quite a few other specialized DC motors, I will again omit here and lastly there are stepper motors. Phew, finally.

A mighty stepper

Stepper motors use direct current too, but they do not rotate quite that easily. Their main specificity regarding the physical construction is that they have multiple windings that can be depending on the stepper construction be mapped to one or multiple so called phases. A phase is in turn mapped to one, two or more steps per full revolution. Thus the stepper.

Why I am writing this? Well I have been experimenting with some stepper drivers lately, as I have already hinted in my previous post about pulse ouputs. Just today I have learned that a 2-phase motor has a very close relative, which is a 3-phase stepper motor. I have already known about the unipolar and bipolar types, but this is again a different taxonomy I have kept for this opportunity. Yeah I know, with so many different types and groups, motors are complicated.

The difference between an unipolar a bipolar are quire nicely explained in many other publications already, so I will not do it here. But the fact the there are 3-phase stepper motors eluded me so far, so I was really surprised seeing the LCDA357H driver with just three terminals to connect the motor labeled U, V and W, instead of A+, A-, B+ and B- for the 2-phase drivers. I have yet to compare both in real application. But a pair of 3-phase kits is already on the way. Both the drivers and the steppers are a little bit more expensive than their 2-phase counterparts but just looking around the Internet, the 3-phase offers many advantages. I'll post the updates on the topic soon.

This is a 86th post of #100daystooffload.