Step 27: Y-Axis Motor Wire Connections
Now we come to the wire connections. To describe the bigger picture, first mechanically, the motors must turn the screw to provide linear power transmission (movement back and forth). The motor needs power to turn the motor shaft, so the motor connects to the driver board that will accept three motor connections, one for each axis. The driver board is connected to a power supply to provide power to the driver board. The computer is also connected to the driver board to provide step pulse and direction instructions.
In this video, I will demonstrate the wire connections to the motor. In the video, I go into a little detail on the motor wire/coil concept. The driver that I assembled is compatible with Unipolar Stepper Motors. Unipolar motors have different combination on how the wires and how many wires are connected. Usually there are 5, 6 or 8 wires for Unipolar motors. There are 4 coils in all, but these coils are separated into pairs, called phases. A coil is a wound-up wire to create an electromagnetic field, when charged). Basically, each phase will provide 2 main wires. That makes 4 wires for two phases. The motor will also include connections (wires) to what is called center taps. Think of a center tap as the center point of the two coils. A 5 wire motor includes only one wire to both center taps (one center tap per phase). 6 wire motors have a wire to each center tap. 8 wire motors separate the coils and provides two wires per coil. In 8 wire motors, two wires on each phase are usually connected to create a single center tap condition. This is the case in my configuration.
So, how do you tell the wires apart if there are no instructions or labeling. That's the hard part, but there is a way (at least for some motors). You can use an ohm meter (multimeter) to determine the resistance from one wire to another. First, a determination of each phase is necessary. the wire connected to a phase and its center tap usually has a very low resistance. The main wires for a phase has a bit higher resistance, due to the fact that the connection must travel through quite a bit of coil. Think if this, why does the chicken cross the street? To get to the other side, right? Ok, the street is a phase, and the yellow line in the middle of the street is the center tap. There are a whole bunch of cars zooming down the street, right? Still with me? The chicken can more easily get to the center tap, than all the way to the other side, with all those cars moving. Then there is that other street a little farther away, on the other side of a tiny earth. Those phase connections will have even more resistance. 5 wire motors are a little more difficult to determine, since both phases are connected together by the common center tap.
Ok, on to the actual connection, the video. A long wire is needed, preferably one with a bundle of wires rapped up in insulation. 22 gauge stranded wire is recommended. Stranded means a bunch of tiny wires that make up one wire, like wire hairs (looks like a pony tail). Gauge is the size of the wire, the lower the number, the bigger it is, sometimes abbreviated AWG. Twisted pair cat 5 is probably not a good choice since it's typically 24 gauge. Make sure to use stranded wire at 22 gauge, very important. Make sure the wire is long enough to provide for the total travel of the axis, but not too long. It is suggested to limit the wire to 6 feet for driver that I'm using.